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1.
  • Anderson, Leif G, 1951, et al. (författare)
  • Shelf-Basin interaction along the East Siberian Sea
  • 2017
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 13:2, s. 349-363
  • Tidskriftsartikel (refereegranskat)abstract
    • Extensive biogeochemical transformation of organic matter takes place in the shallow continental shelf seas of Siberia. This, in combination with brine production from sea-ice formation, results in cold bottom waters with relatively high salinity and nutrient concentrations, as well as low oxygen and pH levels. Data from the SWERUS-C3 expedition with icebreaker Oden, from July to September 2014, show the distribution of such nutrient-rich, cold bottom waters along the continental margin from about 140 to 180 degrees E. The water with maximum nutrient concentration, classically named the upper halocline, is absent over the Lomonosov Ridge at 140 degrees E, while it appears in the Makarov Basin at 150 degrees E and intensifies further eastwards. At the intercept between the Mendeleev Ridge and the East Siberian continental shelf slope, the nutrient maximum is still intense, but distributed across a larger depth interval. The nutrient-rich water is found here at salinities of up to similar to 34.5, i.e. in the water classically named lower halocline. East of 170 degrees E transient tracers show significantly less ventilated waters below about 150 m water depth. This likely results from a local isolation of waters over the Chukchi Abyssal Plain as the boundary current from the west is steered away from this area by the bathymetry of the Mendeleev Ridge. The water with salinities of similar to 34.5 has high nutrients and low oxygen concentrations as well as low pH, typically indicating decay of organic matter. A deficit in nitrate relative to phosphate suggests that this process partly occurs under hypoxia. We conclude that the high nutrient water with salinity similar to 34.5 are formed on the shelf slope in the Mendeleev Ridge region from interior basin water that is trapped for enough time to attain its signature through interaction with the sediment.
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2.
  • Ballarotta, Maxime, et al. (författare)
  • On the glacial and interglacial thermohaline circulation and the associated transports of heat and freshwater
  • 2014
  • Ingår i: Ocean Science. - Gottingen : Copernicus Publications. - 1812-0784 .- 1812-0792. ; 10:6, s. 907-921
  • Tidskriftsartikel (refereegranskat)abstract
    • The thermohaline circulation (THC) and the oceanic heat and freshwater transports are essential for understanding the global climate system. Streamfunctions are widely used in oceanography to represent the THC and estimate the transport of heat and freshwater. In the present study, the regional and global changes of the THC, the transports of heat and freshwater and the timescale of the circulation between the Last Glacial Maximum (LGM, ≈ 21 kyr ago) and the present-day climate are explored using an Ocean General Circulation Model and streamfunctions projected in various coordinate systems. We found that the LGM tropical circulation is about 10% stronger than under modern conditions due to stronger wind stress. Consequently, the maximum tropical transport of heat is about 20% larger during the LGM. In the North Atlantic basin, the large sea-ice extent during the LGM constrains the Gulf Stream to propagate in a more zonal direction, reducing the transport of heat towards high latitudes by almost 50% and reorganising the freshwater transport. The strength of the Atlantic Meridional Overturning Circulation depends strongly on the coordinate system. It varies between 9 and 16 Sv during the LGM, and between 12 to 19 Sv for the present day. Similar to paleo-proxy reconstructions, a large intrusion of saline Antarctic Bottom Water takes place into the Northern Hemisphere basins and squeezes most of the Conveyor Belt circulation into a shallower part of the ocean. These different haline regimes between the glacial and interglacial period are illustrated by the streamfunctions in latitude–salinity coordinates and thermohaline coordinates. From these diagnostics, we found that the LGM Conveyor Belt circulation is driven by an enhanced salinity contrast between the Atlantic and the Pacific basin. The LGM abyssal circulation lifts and makes the Conveyor Belt cell deviate from the abyssal region, resulting in a ventilated upper layer above a deep stagnant layer, and an Atlantic circulation more isolated from the Pacific. An estimate of the timescale of the circulation reveals a sluggish abyssal circulation during the LGM, and a Conveyor Belt circulation that is more vigorous due to the combination of a stronger wind stress and a shortened circulation route.
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3.
  • Beltrán-Abaunza, José M., et al. (författare)
  • Evaluation of MERIS products from Baltic Sea coastal waters rich in CDOM
  • 2014
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 10:3, s. 377-396
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, retrievals of the medium resolution imaging spectrometer (MERIS) reflectances and water quality products using four different coastal processing algorithms freely available are assessed by comparison against sea-truthing data. The study is based on a pair-wise comparison using processor-dependent quality flags for the retrieval of valid common macro-pixels. This assessment is required in order to ensure the reliability of monitoring systems based on MERIS data, such as the Swedish coastal and lake monitoring system (http://vattenkvalitet.se). The results show that the pre-processing with the Improved Contrast between Ocean and Land (ICOL) processor, correcting for adjacency effects, improves the retrieval of spectral reflectance for all processors. Therefore, it is recommended that the ICOL processor should be applied when Baltic coastal waters are investigated. Chlorophyll was retrieved best using the FUB (Free University of Berlin) processing algorithm, although overestimations in the range 18-26.5 %, dependent on the compared pairs, were obtained. At low chlorophyll concentrations (< 2.5 mg m(-3)), data dispersion dominated in the retrievals with the MEGS (MERIS ground segment processor) processor. The lowest bias and data dispersion were obtained with MEGS for suspended particulate matter, for which overestimations in the range of 8-16% were found. Only the FUB retrieved CDOM (coloured dissolved organic matter) correlate with in situ values. However, a large systematic underestimation appears in the estimates that nevertheless may be corrected for by using a local correction factor. The MEGS has the potential to be used as an operational processing algorithm for the Himmerfjarden bay and adjacent areas, but it requires further improvement of the atmospheric correction for the blue bands and better definition at relatively low chlorophyll concentrations in the presence of high CDOM attenuation.
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4.
  • Björk, Göran, 1956, et al. (författare)
  • Bathymetry and oceanic flow structure at two deep passages crossing the Lomonosov Ridge
  • 2018
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 14:1, s. 1-13
  • Tidskriftsartikel (refereegranskat)abstract
    • The Lomonosov Ridge represents a major topographical feature in the Arctic Ocean which has a large effect on the water circulation and the distribution of water properties. This study presents detailed bathymetric survey data along with hydrographic data at two deep passages across the ridge: a southern passage (80-81°ĝN), where the ridge crest meets the Siberian continental slope, and a northern passage around 84.5°ĝN. The southern channel is characterized by smooth and flat bathymetry around 1600–1700ĝm with a sill depth slightly shallower than 1700ĝm. A hydrographic section across the channel reveals an eastward flow with Amundsen Basin properties in the southern part and a westward flow of Makarov Basin properties in the northern part. The northern passage includes an approximately 72ĝkm long and 33ĝkm wide trough which forms an intra-basin in the Lomonosov Ridge morphology (the Oden Trough). The eastern side of the Oden Trough is enclosed by a narrow and steep ridge rising 500–600ĝm above a generally 1600ĝm deep trough bottom. The deepest passage (the sill) is 1470ĝm deep and located on this ridge. Hydrographic data show irregular temperature and salinity profiles indicating that water exchange occurs as midwater intrusions bringing water properties from each side of the ridge in well-defined but irregular layers. There is also morphological evidence that some rather energetic flows may occur in the vicinity of the sill. A well expressed deepening near the sill may be the result of seabed erosion by bottom currents.
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5.
  • Broomé, Sara, 1989-, et al. (författare)
  • Mechanisms of decadal changes in sea surface height and heat content in the eastern Nordic Seas
  • 2020
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 16:3, s. 715-728
  • Tidskriftsartikel (refereegranskat)abstract
    • The Nordic Seas constitute the main ocean conveyor of heat between the North Atlantic Ocean and the Arctic Ocean. Although the decadal variability in the subpolar North Atlantic has been given significant attention lately, especially regarding the cooling trend since the mid-2000s, less is known about the potential connection downstream in the northern basins. Using sea surface heights from satellite altimetry over the past 25 years (1993–2017), we find significant variability on multiyear to decadal timescales in the Nordic Seas. In particular, the regional trends in sea surface height show signs of a weakening since the mid-2000s, as compared to the rapid increase in the preceding decade since the early 1990s. This change is most prominent in the Atlantic origin waters in the eastern Nordic Seas and is closely linked, as estimated from hydrography, to heat content. Furthermore, we formulate a simple heat budget for the eastern Nordic Seas to discuss the relative importance of local and remote sources of variability; advection of temperature anomalies in the Atlantic inflow is found to be the main mechanism. A conceptual model of ocean heat convergence, with only upstream temperature measurements at the inflow to the Nordic Seas as input, is able to reproduce key aspects of the decadal variability in the heat content of the Nordic Seas. Based on these results, we argue that there is a strong connection with the upstream subpolar North Atlantic. However, although the shift in trends in the mid-2000s is coincident in the Nordic Seas and the subpolar North Atlantic, the eastern Nordic Seas have not seen a reversal of trends but instead maintain elevated sea surface heights and heat content in the recent decade considered here.
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6.
  • Caneill, Romain, 1994, et al. (författare)
  • The Southern Ocean deep mixing band emerges from a competition between winter buoyancy loss and upper stratification strength
  • 2024
  • Ingår i: OCEAN SCIENCE. - 1812-0784 .- 1812-0792. ; 20:2, s. 601-619
  • Tidskriftsartikel (refereegranskat)abstract
    • The Southern Ocean hosts a winter deep mixing band (DMB) near the Antarctic Circumpolar Current's (ACC) northern boundary, playing a pivotal role in Subantarctic Mode Water formation. Here, we investigate what controls the presence and geographical extent of the DMB. Using observational data, we construct seasonal climatologies of surface buoyancy fluxes, Ekman buoyancy transport, and upper stratification. The strength of the upper-ocean stratification is determined using the columnar buoyancy index, defined as the buoyancy input necessary to produce a 250 m deep mixed layer. It is found that the DMB lies precisely where the autumn-winter buoyancy loss exceeds the columnar buoyancy found in late summer. The buoyancy loss decreases towards the south, while in the north the stratification is too strong to produce deep mixed layers. Although this threshold is also crossed in the Agulhas Current and East Australian Current regions, advection of buoyancy is able to stabilise the stratification. The Ekman buoyancy transport has a secondary impact on the DMB extent due to the compensating effects of temperature and salinity transports on buoyancy. Changes in surface temperature drive spatial variations in the thermal expansion coefficient (TEC). These TEC variations are necessary to explain the limited meridional extent of the DMB. We demonstrate this by comparing buoyancy budgets derived using varying TEC values with those derived using a constant TEC value. Reduced TEC in colder waters leads to decreased winter buoyancy loss south of the DMB, yet substantial heat loss persists. Lower TEC values also weaken the effect of temperature stratification, partially compensating for the effect of buoyancy loss damping. TEC modulation impacts both the DMB characteristics and its meridional extent.
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7.
  • Castellucci, Valeria, et al. (författare)
  • Sea level variability in the Swedish Exclusive Economic Zone and adjacent seawaters : influence on a point absorbing wave energy converter
  • 2019
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 15, s. 1517-1529
  • Tidskriftsartikel (refereegranskat)abstract
    • Low-frequency sea level variability can be a critical factor for several wave energy converter (WEC) systems, for instance, linear systems with a limited stroke length. Consequently, when investigating suitable areas for deployment of those WEC systems, sea level variability should be taken into account. In order to facilitate wave energy developers finding the most suitable areas for wave energy park installations, this paper describes a study that gives them additional information by exploring the annual and monthly variability of the sea level in the Baltic Sea and adjacent seawaters, with a focus on the Swedish Exclusive Economic Zone. Overall, 10 years of reanalysis data from the Copernicus project have been used to conduct this investigation. The results are presented by means of maps showing the maximum range and the standard deviation of the sea level with a horizontal spatial resolution of about 1 km. A case study illustrates how the results can be used by the WEC developers to limit the energy absorption loss of their devices due to sea level variation. Depending on the WEC technology one wants to examine, the results lead to different conclusions. For the Uppsala point absorber L12 and the sea state considered in the case study, the most suitable sites where to deploy WEC parks from a sea level variation viewpoint are found in the Gotland basins and in the Bothnian Sea, where the energy loss due to sea level variations is negligible.
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8.
  • Castillo, M. I., et al. (författare)
  • Seasonal hydrography and surface outflow in a fjord with a deep sill: the Reloncavi fjord, Chile
  • 2016
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 12:2, s. 533-544
  • Tidskriftsartikel (refereegranskat)abstract
    • Seasonal data on temperature, salinity, dissolved oxygen (DO) and chlorophyll, combined with meteorological and river discharge time series, were used to describe the oceanographic conditions of the Reloncavi fjord (41 degrees 35' S, 72 degrees 20' W). The winds in the fjord valley mainly blow down-fjord during the winter, reinforcing the upper layer outflow, whereas the winds blow predominantly up-fjord during the spring and summer, contrary to the upper layer outflow. The fjord, with a deep sill at the mouth, was well stratified year-round and featured a thin surface layer of brackish water with mean salinities between 10.4 +/- 1.4 (spring) and 13.2 +/- 2.5 (autumn). The depth of the upper layer changed slightly among the different studied seasons but remained at 4.5 m near the mouth. This upper layer presented a mean outflow (Q(1)) of 3185 +/- 223 m(3) s(-1), which implies a flushing time of 3 days for this layer. The vertical salt flux was similar to 37 tons of salt per second, similar to the horizontal salt flux observed in the upper layer. These estimates will contribute to better management of the aquaculture in this region.
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9.
  • Clement Kinney, J., et al. (författare)
  • On the circulation, water mass distribution, and nutrient concentrations of the western Chukchi Sea
  • 2022
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 18:1, s. 29-49
  • Tidskriftsartikel (refereegranskat)abstract
    • Substantial amounts of nutrients and carbon enter the Arctic Ocean from the Pacific Ocean through the Bering Strait, distributed over three main pathways. Water with low salinities and nutrient concentrations takes an eastern route along the Alaskan coast, as Alaskan Coastal Water. A central pathway exhibits intermediate salinity and nutrient concentrations, while the most nutrient-rich water enters the Bering Strait on its western side. Towards the Arctic Ocean, the flow of these water masses is subject to strong topographic steering within the Chukchi Sea with volume transport modulated by the wind field. In this contribution, we use data from several sections crossing Herald Canyon collected in 2008 and 2014 together with numerical modelling to investigate the circulation and transport in the western part of the Chukchi Sea. We find that a substantial fraction of water from the Chukchi Sea enters the East Siberian Sea south of Wrangel Island and circulates in an anticyclonic direction around the island. This water then contributes to the high-nutrient waters of Herald Canyon. The bottom of the canyon has the highest nutrient concentrations, likely as a result of addition from the degradation of organic matter at the sediment surface in the East Siberian Sea. The flux of nutrients (nitrate, phosphate, and silicate) and dissolved inorganic carbon in Bering Summer Water and Winter Water is computed by combining hydrographic and nutrient observations with geostrophic transport referenced to lowered acoustic Doppler current profiler (LADCP) and surface drift data. Even if there are some general similarities between the years, there are differences in both the temperature-salinity and nutrient characteristics. To assess these differences, and also to get a wider temporal and spatial view, numerical modelling results are applied. According to model results, high-frequency variability dominates the flow in Herald Canyon. This leads us to conclude that this region needs to be monitored over a longer time frame to deduce the temporal variability and potential trends. © 2022 Jaclyn Clement Kinney et al.
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10.
  • Drivdal, Magnus, et al. (författare)
  • Wave mixing of buoyant particles: Statfjord A accident as a case study
  • 2014
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 10, s. 977-991
  • Tidskriftsartikel (refereegranskat)abstract
    • This study focuses on how wave–current and wave–turbulence interactions modify the transport of buoy- ant particles in the ocean. Here the particles can repre- sent oil droplets, plastic particles, or plankton such as fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM), modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production, as well as the stronger veering by the Coriolis–Stokes force, affects the drift of the particles. The energy and momentum fluxes, as well as the Stokes drift, depend on the directional wave spectrum ob- tained from a wave model. As a first test, the depth and ve- locity scales from the model are compared with analytical solutions based on a constant eddy viscosity (i.e., classical Ekman theory). Secondly, the model is applied to a case in which we investigate the oil drift after an oil spill off the west coast of Norway in 2007. During this accident the aver- age net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by oil- drift models. In this case, using wind and wave forcing from the ERA Interim archive it is shown that the wave effects are important for the resultant drift and have the potential to im- prove drift forecasting.
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11.
  • Droste, E. S., et al. (författare)
  • The influence of tides on the marine carbonate chemistry of a coastal polynya in the south-eastern Weddell Sea
  • 2022
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 18:5, s. 1293-1320
  • Tidskriftsartikel (refereegranskat)abstract
    • Tides significantly affect polar coastlines by modulating ice shelf melt and modifying shelf water properties through transport and mixing. However, the effect of tides on the marine carbonate chemistry in such regions, especially around Antarctica, remains largely unexplored. We address this topic with two case studies in a coastal polynya in the south-eastern Weddell Sea, neighbouring the Ekstrom Ice Shelf. The case studies were conducted in January 2015 (PS89) and January 2019 (PS117), capturing semi-diurnal oscillations in the water column. These are pronounced in both physical and biogeochemical variables for PS89. During rising tide, advection of sea ice meltwater from the north-east created a fresher, warmer, and more deeply mixed water column with lower dissolved inorganic carbon (DIC) and total alkalinity (TA) content. During ebbing tide, water from underneath the ice shelf decreased the polynya's temperature, increased the DIC and TA content, and created a more stratified water column. The variability during the PS117 case study was much smaller, as it had less sea ice meltwater input during rising tide and was better mixed with sub-ice shelf water. The contrasts in the variability between the two case studies could be wind and sea ice driven, and they underline the complexity and highly dynamic nature of the system. The variability in the polynya induced by the tides results in an air-sea CO2 flux that can range between a strong sink (-24 mmol m(-2) d(-1)) and a small source (3 mmol m(-2) d(-1)) on a semi-diurnal timescale. If the variability induced by tides is not taken into account, there is a potential risk of overestimating the polynya's CO2 uptake by 67 % or underestimating it by 73 %, compared to the average flux determined over several days. Depending on the timing of limited sampling, the polynya may appear to be a source or a sink of CO2. Given the disproportionate influence of polynyas on heat and carbon exchange in polar oceans, we recommend future studies around the Antarctic and Arctic coastlines to consider the timing of tidal currents in their sampling strategies and analyses. This will help constrain variability in oceanographic measurements and avoid potential biases in our understanding of these highly complex systems.
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12.
  • Dubois, Kévin, 1995-, et al. (författare)
  • Technical note : Extending sea level time series for the analysis of extremes with statistical methods and neighbouring station data
  • 2024
  • Ingår i: Ocean Science. - : Copernicus Publications. - 1812-0784 .- 1812-0792. ; 20:1, s. 21-30
  • Tidskriftsartikel (refereegranskat)abstract
    • Extreme sea levels may cause damage and the disruption of activities in coastal areas. Thus, predicting extreme sea levels is essential for coastal management. Statistical inference of robust return level estimates critically depends on the length and quality of the observed time series. Here, we compare two different methods for extending a very short (∼ 10-year) time series of tide gauge measurements using a longer time series from a neighbouring tide gauge: linear regression and random forest machine learning. Both methods are applied to stations located in the Kattegat Basin between Denmark and Sweden. Reasonable results are obtained using both techniques, with the machine learning method providing a better reconstruction of the observed extremes. By generating a set of stochastic time series reflecting uncertainty estimates from the machine learning model and subsequently estimating the corresponding return levels using extreme value theory, the spread in the return levels is found to agree with results derived by more physically based methods.
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13.
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14.
  • Gao, Qiuju, et al. (författare)
  • On the chemical dynamics of extracellular polysaccharides in the high Arctic surface microlayer
  • 2012
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 8:4, s. 401-418
  • Tidskriftsartikel (refereegranskat)abstract
    • The surface microlayer (SML) represents a unique system of which the physicochemical characteristics may differ from those of the underlying subsurface seawater (SSW). Within the Arctic pack ice area, the SML has been characterized as enriched in small colloids of biological origin, resulting from extracellular polymeric secretions (EPS). During the Arctic Summer Cloud-Ocean Study (ASCOS) in August 2008, particulate and dissolved organic matter (POM, DOM) samples were collected and chemically characterized from the SML and the corresponding SSW at an open lead centered at 87.5° N and 5°E.  Total organic carbon was persistently enriched in the SML with a mean enrichment factor (EF) of 1.45 ± 0.41, whereas sporadic depletions of dissolved carbohydrates and amino acids were observed. Monosaccharide compositional analysis reveals that EPS in the Arctic lead was formed mainly of distinctive heteropolysaccharides, enriched in xylose, fucose and glucose. The mean concentrations of total hydrolysable neutral sugars in SSW were 94.9 ± 37.5 nM in high molecular weight (HMW) DOM and 64.4 ± 14.5 nM in POM. The enrichment of polysaccharides in the SML appeared to be a common feature, with EFs ranging from 1.7 to 7.0 for particulate polysaccharides and 3.5 to 12.1 for polysaccharides in the HMW DOM fraction. A calculated monosaccharide yield suggests that polymers in the HMW DOM fraction were scavenged, without substantial degradation, into the SML.  Bubble scavenging experiments showed that newly aggregated particles could be formed abiotically by coagulation of low molecular weight nanometer-sized gels. Experimentally-generated aerosol particles were enriched in polysaccharides by factors of 22-70, relative to the source seawater. We propose that bubble scavenging of surface-active polysaccharides was one of the possible mechanisms for the enrichment of polysaccharides in the SML.
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15.
  • Geoffroy, Gaspard, 1991-, et al. (författare)
  • Validating the spatial variability in the semidiurnal internal tide in a realistic global ocean simulation with Argo and mooring data
  • 2023
  • Ingår i: Ocean Science. - 1812-0784 .- 1812-0792. ; 19:3, s. 811-835
  • Tidskriftsartikel (refereegranskat)abstract
    • The autocovariance of the semidiurnal internal tide (IT) is examined in a 32 d segment of a global run of the HYbrid Coordinate Ocean Model (HYCOM). This numerical simulation, with 41 vertical layers and ∘ horizontal resolution, includes tidal and atmospheric forcing, allowing for the generation and propagation of ITs to take place within a realistic eddying general circulation. The HYCOM data are in turn compared with global observations of the IT around 1000 dbar, from Argo float park-phase data and mooring records. HYCOM is found to be globally biased low in terms of the IT variance and decay of the IT autocovariance over timescales shorter than 32 d. Except in the Southern Ocean, where limitations in the model cause the discrepancy with in situ measurements to grow poleward, the spatial correlation between the Argo and HYCOM tidal variance suggests that the generation of low-mode semidiurnal ITs is globally well captured by the model.
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16.
  • Heuzé, Céline, 1988 (författare)
  • Antarctic Bottom Water and North Atlantic Deep Water in CMIP6 models
  • 2021
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 17:1, s. 59-90
  • Tidskriftsartikel (refereegranskat)abstract
    • Deep and bottom water formation are crucial components of the global ocean circulation, yet they were poorly represented in the previous generation of climate models. We here quantify biases in Antarctic Bottom Water (AABW) and North Atlantic Deep Water (NADW) formation, properties, transport, and global extent in 35 climate models that participated in the latest Climate Model Intercomparison Project (CMIP6). Several CMIP6 models are correctly forming AABW via shelf processes, but 28 models in the Southern Ocean and all 35 models in the North Atlantic form deep and bottom water via open-ocean deep convection too deeply, too often, and/or over too large an area. Models that convect the least form the most accurate AABW but the least accurate NADW. The four CESM2 models with their overflow parameterisation are among the most accurate models. In the Atlantic, the colder the AABW, the stronger the abyssal overturning at 30 degrees S, and the further north the AABW layer extends. The saltier the NADW, the stronger the Atlantic Meridional Overturning Circulation (AMOC), and the further south the NADW layer extends. In the Indian and Pacific oceans in contrast, the fresher models are the ones which extend the furthest regardless of the strength of their abyssal overturning, most likely because they are also the models with the weakest fronts in the Antarctic Circumpolar Current. There are clear improvements since CMIP5: several CMIP6 models correctly represent or parameterise Antarctic shelf processes, fewer models exhibit Southern Ocean deep convection, more models convect at the right location in the Labrador Sea, bottom density biases are reduced, and abyssal overturning is more realistic. However, more improvements are required, e.g. by generalising the use of overflow parameterisations or by coupling to interactive ice sheet models, before deep and bottom water formation, and hence heat and carbon storage, are represented accurately.
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17.
  • Heuzé, Céline, 1988 (författare)
  • North Atlantic deep water formation and AMOC in CMIP5 models
  • 2017
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 13, s. 609-622
  • Tidskriftsartikel (refereegranskat)abstract
    • Deep water formation in climate models is indicative of their ability to simulate future ocean circulation, carbon and heat uptake, and sea level rise. Present-day temperature, salinity, sea ice concentration and ocean transport in the North Atlantic subpolar gyre and Nordic Seas from 23 CMIP5 (Climate Model Intercomparison Project, phase 5) models are compared with observations to assess the biases, causes and consequences of North Atlantic deep convection in models. The majority of models convect too deep, over too large an area, too often, and too far south. Deep convection occurs at the sea ice edge and is most realistic in models with accurate sea ice extent, mostly those using the CICE model. Half of the models convect in response to local cooling or salinification of the surface waters; only a third have a dynamic relationship between freshwater coming from the Arctic and deep convection. The models with the most intense deep convection have the warmest deep waters, due to a redistribution of heat through the water column. For the majority of models, the variability of the Atlantic Meridional Overturning Circulation (AMOC) is explained by the volumes of deep water produced in the subpolar gyre and Nordic Seas up to 2 years before. In turns, models with the strongest AMOC have the largest heat export to the Arctic. Understanding the dynamical drivers of deep convection and AMOC in models is hence key to realistically forecast Arctic oceanic warming and its consequences on the global ocean circulation, cryosphere and marine life.
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18.
  • Jakobsson, Martin, et al. (författare)
  • Bathymetric properties of the Baltic Sea
  • 2019
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 15:4, s. 905-924
  • Tidskriftsartikel (refereegranskat)abstract
    • Baltic Sea bathymetric properties are analysed here using the newly released digital bathymetric model (DBM) by the European Marine Observation and Data Network (EMODnet). The analyses include hypsometry, volume, descriptive depth statistics, and kilometre-scale seafloor ruggedness, i.e. terrain heterogeneity, for the Baltic Sea as a whole as well as for 17 sub-basins defined by the Baltic Marine Environment Protection Commission (HELCOM). We compare the new EMODnet DBM with IOWTOPO the previously most widely used DBM of the Baltic Se aproduced by the Leibniz-Institut fur Ostseeforschung Warnemiinde (IOW), which has served as the primary gridded bathymetric resource in physical and environmental studies for nearly two decades. The area of deep water exchange between the Bothnian Sea and the Northern Baltic Proper across the Aland Sea is specifically analysed in terms of depths and locations of critical bathymetric sills. The EMODnet DBM provides a bathymetric sill depth of 88 m at the northern side of the Aland Sea and 60 m at the southern side, differing from previously identified sill depths of 100 and 70 m, respectively. High-resolution multibeam bathymetry acquired from this deep water exchange path, where vigorous bottom currents interacted with the seafloor, allows us to assess what presently available DBMs are missing in terms of physical characterization of the seafloor. Our study highlights the need for continued work towards complete high-resolution mapping of the Baltic Sea seafloor.
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19.
  • Jalkanen, Jukka-Pekka, et al. (författare)
  • Modelling of discharges from Baltic Sea shipping
  • 2021
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792.
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper describes the new developments of the Ship Traffic Emission Assessment Model (STEAM) which enable the modelling of pollutant discharges to water from ships. These include nutrients from black/grey water discharges as well as from food waste. Further, the modelling of contaminants in ballast, black, grey and scrubber water, bilge discharges, and stern tube oil leaks are also described as well as releases of contaminants from antifouling paints.Each of the discharges is regulated by different sections of the IMO MARPOL convention, and emission patterns of different pollution releases vary significantly. The discharge patterns and total amounts for the year 2012 in the Baltic Sea area are reported and open-loop SOx scrubbing effluent was found to be the second-largest pollutant stream by volume. The scrubber discharges have increased significantly in recent years, and their environmental impacts need to be investigated in detail.
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20.
  • Jalkanen, J. P., et al. (författare)
  • Modelling of ships as a source of underwater noise
  • 2018
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0792 .- 1812-0784. ; 14:6, s. 1373-1383
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, a methodology is presented for modelling underwater noise emissions from ships based on realistic vessel activity in the Baltic Sea region. This paper combines the Wittekind noise source model with the Ship Traffic Emission Assessment Model (STEAM) in order to produce regular updates for underwater noise from ships. This approach allows the construction of noise source maps, but requires parameters which are not commonly available from commercial ship technical databases. For this reason, alternative methods were necessary to fill in the required information. Most of the parameters needed contain information that is available during the STEAM model runs, but features describing propeller cavitation are not easily recovered for the world fleet. Baltic Sea ship activity data were used to generate noise source maps for commercial shipping. Container ships were recognized as the most significant source of underwater noise, and the significant potential for an increase in their contribution to future noise emissions was identified.
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21.
  • Johansson, Lasse, et al. (författare)
  • Model for leisure boat activities and emissions – implementation for the Baltic Sea
  • 2020
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0792 .- 1812-0784. ; 16:5, s. 1143-1163
  • Tidskriftsartikel (refereegranskat)abstract
    • The activities and emissions from leisure boats in the Baltic Sea have been modeled in a comprehensive approach for the first time, using a new simulation model leisure Boat Emissions and Activities siMulator (BEAM). The model utilizes survey data to characterize the national leisure boat fleets. Leisure boats have been categorized based on their size, use and engine specifications, and for these subcategories emission factors for NOx, PM2.5, CO, non-methane volatile organic compounds (NMVOCs), and releases of copper (Cu) and zinc (Zn) from antifouling paints have been estimated according to literature values. The modeling approach also considers the temporal and spatial distribution of leisure boat activities, which are applied to each simulated leisure boat separately. According to our results the CO and NMVOC emissions from leisure boats, as well as Cu and Zn released from antifouling paints, are significant when compared against the emissions originating from registered commercial shipping in the Baltic Sea. CO emissions equal 70 % of the registered shipping emissions and NMVOC emissions equal 160 % when compared against the modeled results in the Baltic Sea in 2014. Modeled NOx and PM2.5 from the leisure boats are less significant compared to the registered shipping emissions. The emissions from leisure boats are concentrated in the summer months of June, July and August and are released in the vicinity of inhabited coastal areas. Given the large emission estimates for leisure boats, this commonly overlooked source of emissions should be further investigated in greater detail.
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22.
  • Karam, Salar, et al. (författare)
  • Continued warming of deep waters in the Fram Strait
  • 2024
  • Ingår i: OCEAN SCIENCE. - 1812-0784 .- 1812-0792. ; 20:4, s. 917-930
  • Tidskriftsartikel (refereegranskat)abstract
    • The Fram Strait is the only deep gateway between the Arctic and the rest of the World Ocean, and it is thus a key region to understand how the deep Arctic will evolve. However, studies and data regarding the deep ocean are scarce, making it difficult to understand its role in the climate system. Here, we analyse oceanographic data obtained close to the Fram Strait sill depth of 2500 m by two long-term mooring locations (F11 and HG-FEVI) in the Fram Strait between 2010-2023 to investigate long-term changes in the hydrographic properties. For additional context, we compile hydrographic profile data from the 1980s for the adjacent basins: the Greenland Sea and the Eurasian Basin. At mooring F11 in the western Fram Strait, we find a clear seasonality, with increased Greenland Sea Deep Water (GSDW) presence during summer and increased Eurasian Basin Deep Water (EBDW) presence during winter. Evaluating long-term changes, we find a modest temperature increase of similar to 0.1 degrees C for EBDW from the 1980s. For GSDW, south of the Fram Strait, we find a strong temperature increase of similar to 0.4-0.5 degrees C for the same period. The different warming rates have led to GSDW becoming warmer than EBDW since similar to 2017-2018. This means that the Greenland Sea is no longer a heat sink for the Arctic Ocean at depth but is rather a heat source. It is therefore possible that EBDW temperatures will increase faster in the future.
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23.
  • Mcdougall, Trevor J., et al. (författare)
  • A thermodynamic potential of seawater in terms of Absolute Salinity, Conservative Temperature, and in situ pressure
  • 2023
  • Ingår i: OCEAN SCIENCE. - 1812-0784 .- 1812-0792. ; 19:6, s. 1719-1741
  • Tidskriftsartikel (refereegranskat)abstract
    • A thermodynamic potential is derived for seawater as a function of Conservative Temperature, Absolute Salinity and pressure. From this thermodynamic potential, all the equilibrium thermodynamic properties of seawater can be found, just as all these thermodynamic properties can be found from the TEOS-10 (the International Thermodynamic Equation of Seawater - 2010; IOC et al., 2010) Gibbs function (which is a function of in situ temperature, Absolute Salinity, and pressure). Present oceanographic practice in the Gibbs SeaWater Oceanographic Toolbox uses a polynomial expression for specific volume (and enthalpy) in terms of Conservative Temperature (as well as of Absolute Salinity and pressure), whereas the relationship between in situ temperature and Conservative Temperature is based on the Gibbs function. This mixed practice introduces (numerically small) inconsistencies and superfluous conversions between variables. The proposed thermodynamic potential of seawater, being expressed as an explicit function of Conservative Temperature, overcomes these small numerical inconsistencies, and in addition, the new approach allows for greater computational efficiency in the evaluation of sea surface temperature from Conservative Temperature. It is also shown that when using Conservative Temperature, the thermodynamic information in enthalpy is independent of that contained in entropy. This contrasts with the cases where either in situ temperature or potential temperature is used. In these cases, a single thermodynamic potential serves the important purpose of avoiding having to impose a separate consistency requirement between the functional forms of enthalpy and entropy.
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24.
  • Norris, S. J., et al. (författare)
  • Measurements of bubble size spectra within leads in the Arctic summer pack ice
  • 2011
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 7:1, s. 129-139
  • Tidskriftsartikel (refereegranskat)abstract
    • The first measurements of bubble size spectra within the near-surface waters of open leads in the central Arctic pack ice were obtained during the Arctic Summer Cloud-Ocean Study (ASCOS) in August 2008 at 8787.6 degrees N, 1-11 degrees W. A significant number of small bubbles (30-100 mu m diameter) were present, with concentration decreasing rapidly with size from 100-560 mu m; no bubbles larger than 560 mu m were observed. The bubbles were present both during periods of low wind speed (U < 6 m s(-1)) and when ice covered the surface of the lead. The low wind and short open-water fetch precludes production of bubbles by wave breaking suggesting that the bubbles are generated by processes below the surface. When the surface water was open to the atmosphere bubble concentrations increased with increasing heat loss to the atmosphere. The presence of substantial numbers of bubbles is significant because the bursting of bubbles at the surface provides a mechanism for the generation of aerosol and the ejection of biological material from the ocean into the atmosphere. Such a transfer has previously been proposed as a potential climate feedback linking marine biology and Arctic cloud properties.
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25.
  • Nylund, Amanda, 1989, et al. (författare)
  • In situ observations of turbulent ship wakes and their spatiotemporal extent
  • 2021
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0792 .- 1812-0784. ; 17:5, s. 1285-1302
  • Tidskriftsartikel (refereegranskat)abstract
    • In areas of intensive ship traffic, ships pass every 10ĝ€¯min. Considering the amount of ship traffic and the predicted increase in global maritime trade, there is a need to consider all types of impacts shipping has on the marine environment. While the awareness about, and efforts to reduce, chemical pollution from ships is increasing, less is known about physical disturbances, and ship-induced turbulence has so far been completely neglected. To address the potential importance of ship-induced turbulence on, e.g., gas exchange, dispersion of pollutants, and biogeochemical processes, a characterisation of the temporal and spatial scales of the turbulent wake is needed. Currently, field measurements of turbulent wakes of real-size ships are lacking. This study addresses that gap by using two different methodological approaches: in situ and ex situ observations. For the in situ observations, a bottom-mounted acoustic Doppler current profiler (ADCP) was placed at 32ĝ€¯m depth below the shipping lane outside Gothenburg harbour. Both the acoustic backscatter from the air bubbles in the wake and the dissipation rate of turbulent kinetic energy were used to quantify the turbulent wake depth, intensity, and temporal longevity for 38 ship passages of differently sized ships. The results from the ADCP measurements show median wake depths of 13ĝ€¯m and several occasions of wakes reaching depths >ĝ€¯18ĝ€¯m, which is in the same depth range as the seasonal thermocline in the Baltic Sea. The temporal longevity of the observable part of the wakes had a median of around 10ĝ€¯min and several passages of >ĝ€¯20ĝ€¯min. In the ex situ approach, sea surface temperature was used as a proxy for the water mass affected by the turbulent wake (thermal wake), as lowered temperature in the ship wake indicates vertical mixing in a thermally stratified water column. Satellite images of the thermal infrared sensor (TIRS) onboard Landsat-8 were used to measure thermal wake width and length, in the highly frequented and thus major shipping lane north of Bornholm, Baltic Sea. Automatic information system (AIS) records from both the investigated areas were used to identify the ships inducing the wakes. The satellite analysis showed a median thermal wake length of 13.7ĝ€¯km (nCombining double low line144), and the longest wake extended over 60ĝ€¯km, which would correspond to a temporal longevity of 1ĝ€¯h 42ĝ€¯min (for a ship speed of 20ĝ€¯kn). The median thermal wake width was 157.5ĝ€¯m. The measurements of the spatial and temporal scales are in line with previous studies, but the maximum turbulent wake depth (30.5ĝ€¯m) is deeper than previously reported. The results from this study, combined with the knowledge of regional high traffic densities, show that ship-induced turbulence occurs at temporal and spatial scales large enough to imply that this process should be considered when estimating environmental impacts from shipping in areas with intense ship traffic.
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26.
  • Oelerich, Ria, et al. (författare)
  • Stirring across the Antarctic Circumpolar Current's southern boundary at the prime meridian, Weddell Sea
  • 2023
  • Ingår i: Ocean Science. - 1812-0784 .- 1812-0792. ; 19:5, s. 1465-1482
  • Tidskriftsartikel (refereegranskat)abstract
    • At the southern boundary of the Antarctic Circumpolar Current (ACC), relatively warm ACC waters encounter the colder waters surrounding Antarctica. Strong density gradients across the southern boundary indicate the presence of a frontal jet and are thought to modulate the southward heat transport across the front. In this study, the southern boundary in the Weddell Sea sector at the prime meridian is surveyed for the first time in high resolution over 2 months during an austral summer with underwater gliders occupying a transect across the front on five occasions. The five transects show that the frontal structure (i.e. hydrography, velocities and lateral density gradients) varies temporally. The results demonstrate significant, transient (a few weeks) variability of the southern boundary and its frontal jet in location, strength and width. A mesoscale cold-core eddy is identified to disrupt the southern boundary's frontal structure and strengthen lateral density gradients across the front. The front's barrier properties are assessed using mixing length scales and potential vorticity to establish the cross-frontal exchange of properties between the ACC and the Weddell Gyre. The results show that stronger lateral density gradients caused by the mesoscale eddy strengthen the barrier-like properties of the front through reduced mixing length scales and pronounced gradients of potential vorticity. In contrast, the barrier-like properties of the southern boundary are reduced when no mesoscale eddy is influencing the density gradients across the front. Using satellite altimetry, we further demonstrate that the barrier properties over the past decade have strengthened as a result of increased meridional gradients of absolute dynamic topography and increased frontal jet speeds in comparison to previous decades. Our results emphasise that locally and rapidly changing barrier properties of the southern boundary are important to quantify the cross-frontal exchange, which is particularly relevant in regions where the southern boundary is located near the Antarctic shelf break (e.g. in the West Antarctic sector).
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27.
  • Pauthenet, E., et al. (författare)
  • Four-dimensional temperature, salinity and mixed-layer depth in the Gulf Stream, reconstructed from remote-sensing and in situ observations with neural networks
  • 2022
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 18:4, s. 1221-1244
  • Tidskriftsartikel (refereegranskat)abstract
    • Despite the ever-growing number of ocean data, the interior of the ocean remains undersampled in regions of high variability such as the Gulf Stream. In this context, neural networks have been shown to be effective for interpolating properties and understanding ocean processes. We introduce OSnet (Ocean Stratification network), a new ocean reconstruction system aimed at providing a physically consistent analysis of the upper ocean stratification. The proposed scheme is a bootstrapped multilayer perceptron trained to predict simultaneously temperature and salinity (T - S) profiles down to 1000 m and the mixed-layer depth (MLD) from surface data covering 1993 to 2019. OSnet is trained to fit sea surface temperature and sea level anomalies onto all historical in situ profiles in the Gulf Stream region. To achieve vertical coherence of the profiles, the MLD prediction is used to adjust a posteriori the vertical gradients of predicted T - S profiles, thus increasing the accuracy of the solution and removing vertical density inversions. The prediction is generalized on a 1/4 degrees daily grid, producing four-dimensional fields of temperature and salinity, with their associated confidence interval issued from the bootstrap. OSnet profiles have root mean square error comparable with the observation-based Armor3D weekly product and the physics-based ocean reanalysis Glorys12. The lowest confidence in the prediction is located north of the Gulf Stream, between the shelf and the current, where the thermohaline variability is large. The OSnet reconstructed field is coherent even in the pre-Argo years, demonstrating the good generalization properties of the network. It reproduces the warming trend of surface temperature, the seasonal cycle of surface salinity and mesoscale structures of temperature, salinity and MLD. While OSnet delivers an accurate interpolation of the ocean stratification, it is also a tool to study how the ocean stratification relates to surface data. We can compute the relative importance of each input for each T - S prediction and analyse how the network learns which surface feature influences most which property and at which depth. Our results demonstrate the potential of machine learning methods to improve predictions of ocean interior properties from observations of the ocean surface.
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28.
  • Pipko, Irina, et al. (författare)
  • The spatial and interannual dynamics of the surface water carbonate system and air–sea CO2 fluxes in the outer shelf and slope of the Eurasian Arctic Ocean
  • 2017
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 13, s. 997-1016
  • Tidskriftsartikel (refereegranskat)abstract
    • The Arctic is undergoing dramatic changes which cover the entire range of natural processes, from extreme increases in the temperatures of air, soil, and water, to changes in the cryosphere, the biodiversity of Arctic waters, and land vegetation. Small changes in the largest marine carbon pool, the dissolved inorganic carbon pool, can have a profound impact on the carbon dioxide (CO2) flux between the ocean and the atmosphere, and the feedback of this flux to climate. Knowledge of relevant processes in the Arctic seas improves the evaluation and projection of carbon cycle dynamics under current conditions of rapid climate change. Investigation of the CO2 system in the outer shelf and continental slope waters of the Eurasian Arctic seas (the Barents, Kara, Laptev, and East Siberian seas) during 2006, 2007, and 2009 revealed a general trend in the surface water partial pressure of CO2 (pCO2) distribution, which manifested as an increase in pCO2 values eastward. The existence of this trend was defined by different oceanographic and biogeochemical regimes in the western and eastern parts of the study area; the trend is likely increasing due to a combination of factors determined by contemporary change in the Arctic climate, each change in turn evoking a series of synergistic effects. A high-resolution in situ investigation of the carbonate system parameters of the four Arctic seas was carried out in the warm season of 2007; this year was characterized by the next-to-lowest historic sea-ice extent in the Arctic Ocean, on satellite record, to that date. The study showed the different responses of the seawater carbonate system to the environment changes in the western vs. the eastern Eurasian Arctic seas. The large, open, highly productive water area in the northern Barents Sea enhances atmospheric CO2 uptake. In contrast, the uptake of CO2 was strongly weakened in the outer shelf and slope waters of the East Siberian Arctic seas under the 2007 environmental conditions. The surface seawater appears in equilibrium or slightly supersaturated by CO2 relative to atmosphere because of the increasing influence of river runoff and its input of terrestrial organic matter that mineralizes, in combination with the high surface water temperature during sea-ice-free conditions. This investigation shows the importance of processes that vary on small scales, both in time and space, for estimating the air–sea exchange of CO2. It stresses the need for high-resolution coverage of ocean observations as well as time series. Furthermore, time series must include multi-year studies in the dynamic regions of the Arctic Ocean during these times of environmental change.
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29.
  • Poropat, Lea, 1989, et al. (författare)
  • Unsupervised classification of the northwestern European seas based on satellite altimetry data
  • 2024
  • Ingår i: OCEAN SCIENCE. - 1812-0784 .- 1812-0792. ; 20:1, s. 201-215
  • Tidskriftsartikel (refereegranskat)abstract
    • From generating metrics representative of a wide region to saving costs by reducing the density of an observational network, the reasons to split the ocean into distinct regions are many. Traditionally, this has been done somewhat arbitrarily using the bathymetry and potentially some artificial latitude-longitude boundaries. We use an ensemble of Gaussian mixture models (GMMs, unsupervised classification) to separate the complex northwestern European coastal region into classes based on sea level variability observed by satellite altimetry. To reduce the dimensionality of the data, we perform a principal component analysis on 27 years of observations and use the spatial components as input for the GMM. The number of classes or mixture components is determined by locating the maximum of the silhouette score and by testing several models. We use an ensemble approach to increase the robustness of the classification and to allow the separation into more regions than a single GMM can achieve. We also vary the number of empirical orthogonal function (EOF) maps and show that more EOFs result in a more detailed classification. With three EOFs, the area is classified into four distinct regions delimited mainly by bathymetry. Adding more EOFs results in further subdivisions that resemble oceanic fronts. To achieve a more detailed separation, we use a model focused on smaller regions, specifically the Baltic Sea, North Sea, and the Norwegian Sea.
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30.
  • Possenti, L., et al. (författare)
  • Norwegian Sea net community production estimated from O-2 and prototype CO2 optode measurements on a Seaglider
  • 2021
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 17:2, s. 593-614
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on a pilot study using a CO2 optode deployed on a Seaglider in the Norwegian Sea from March to October 2014. The optode measurements required drift and lag correction and in situ calibration using discrete water samples collected in the vicinity. We found that the optode signal correlated better with the concentration of CO2, c(CO2), than with its partial pressure, p(CO2). Using the calibrated c(CO2) and a regional parameterisation of total alkalinity (AT) as a function of temperature and salinity, we calculated total dissolved inorganic carbon content, c(DIC), which had a standard deviation of 11 mu mol kg(-1) compared with in situ measurements. The glider was also equipped with an oxygen (O-2) optode. The O-2 optode was drift corrected and calibrated using a c(O-2) climatology for deep samples. The calibrated data enabled the calculation of DIC- and O-2-based net community production, N (DIC) and N (O-2). To derive N, DIC and O-2 inventory changes over time were combined with estimates of air-sea gas exchange, diapycnal mixing and entrainment of deeper waters. Glider-based observations captured two periods of increased Chl a inventory in late spring (May) and a second one in summer (June). For the May period, we found N (DIC) = (21 +/- 5) mmol m(-2) d(-1), N (O-2) = (94 +/- 16) mmol m(-2) d(-1) and an (uncalibrated) Chl a peak concentration of c(raw)(Chl a) = 3 mg m(-3). During the June period, c(raw)(Chl a) increased to a summer maximum of 4 mg m(-3), associated with N (DIC) = (85 +/- 5) mmol m(-2) d(-1) and N (O-2) = (126 +/- 25) mmol m(-2) d(-1). The high-resolution dataset allowed for quantification of the changes in N before, during and after the periods of increased Chl a inventory. After the May period, the remineralisation of the material produced during the period of increased Chl a inventory decreased N (DIC) to (-3 +/- 5) mmol m(-2) d(-1) and N (O-2) to (0 +/- 2) mmol m(-2) d(-1). The survey area was a source of O-2 and a sink of CO2 for most of the summer. The deployment captured two different surface waters influenced by the Norwegian Atlantic Current (NwAC) and the Norwegian Coastal Current (NCC). The NCC was characterised by lower c (O-2) and c(DIC) than the NwAC, as well as lower N (O-2) and craw(Chl a) but higher N (DIC). Our results show the potential of glider data to simultaneously capture time- and depth-resolved variability in DIC and O-2 concentrations.
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31.
  • Pugach, Svetlana P., et al. (författare)
  • Dissolved organic matter and its optical characteristics in the Laptev and East Siberian seas : spatial distribution and interannual variability (2003-2011)
  • 2018
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 14:1, s. 87-103
  • Tidskriftsartikel (refereegranskat)abstract
    • The East Siberian Arctic Shelf (ESAS) is the broadest and shallowest continental shelf in the world. It is characterized by both the highest rate of coastal erosion in the world and a large riverine input of terrigenous dissolved organic matter (DOM). DOM plays a significant role in marine aquatic ecosystems. The chromophoric fraction of DOM (CDOM) directly affects the quantity and spectral quality of available light, thereby impacting both primary production and ultraviolet (UV) exposure in aquatic ecosystems. A multiyear study of CDOM absorption, fluorescence, and spectral characteristics was carried out over the vast ESAS in the summer-fall seasons. The paper describes observations accomplished at 286 stations and 1766 in situ high-resolution optical measurements distributed along the nearshore zone. Spatial and interannual CDOM dynamics over the ESAS were investigated, and driving factors were identified. It was shown that the atmospheric circulation regime is the dominant factor controlling CDOM distribution on the ESAS. This paper explores the possibility of using CDOM and its spectral parameters to identify the different biogeochemical regimes in the surveyed area. The analysis of CDOM spectral characteristics showed that the major part of the Laptev and East Siberian seas shelf is influenced by terrigenous DOM carried in riverine discharge. Western and eastern provinces of the ESAS with distinctly different DOM optical properties were also identified; a transition between the two provinces at around 165-170 degrees E, also consistent with hydrological and hydrochemical data, is shown. In the western ESAS, a region of substantial river impact, the content of aromatic carbon within DOM remains almost constant. In the eastern ESAS, a gradual decrease in aromaticity percentage was observed, indicating contribution of Pacific-origin waters, where allochthonous DOM with predominantly aliphatic character and much smaller absorption capacity predominates. In addition, we found a stable tendency towards reduced concentrations of CDOM and dissolved lignin and an increase in spectral slope and slope ratio values eastward from the Lena River delta; the Lena is the main supplier of DOM to the eastern Arctic shelf. The strong positive correlation (r = 0.97) between dissolved organic carbon (DOC) and CDOM values in the surface shelf waters influenced by terrigenous discharge indicates that it is feasible to estimate DOC content from CDOM fluorescence assessed in situ using a WETStar fluorometer. This approach is reliable over the salinity range of 3 to 24.5. The fact that there is little difference between predicted and observed parameters indicates that the approach is justified. The direct estimation of DOM optical characteristics in the surface ESAS waters provided by this multiyear study will also be useful for validating and calibrating remote sensing data.
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32.
  • Rudels, B., et al. (författare)
  • Observations of water masses and circulation with focus on the Eurasian Basin of the Arctic Ocean from the 1990s to the late 2000s
  • 2013
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 9:1, s. 147-169
  • Tidskriftsartikel (refereegranskat)abstract
    • The circulation and water mass properties in the Eurasian Basin are discussed based on a review of previous research and an examination of observations made in recent years within, or parallel to, DAMOCLES (Developing Arctic Modeling and Observational Capabilities for Long-term Environmental Studies). The discussion is strongly biased towards observations made from icebreakers and particularly from the cruise with R/V Polarstern 2007 during the International Polar Year (IPY). Focus is on the Barents Sea inflow branch and its mixing with the Fram Strait inflow branch. It is proposed that the Barents Sea branch contributes not just intermediate water but also most of the water to the Atlantic layer in the Amundsen Basin and also in the Makarov and Canada basins. Only occasionally would high temperature pulses originating from the Fram Strait branch penetrate along the Laptev Sea slope across the Gakkel Ridge into the Amundsen Basin. Interactions between the Barents Sea and the Fram Strait branches lead to formation of intrusive layers, in the Atlantic layer and in the intermediate waters. The intrusion characteristics found downstream, north of the Laptev Sea are similar to those observed in the northern Nansen Basin and over the Gakkel Ridge, suggesting a flow from the Laptev Sea towards Fram Strait. The formation mechanisms for the intrusions at the continental slope, or in the interior of the basins if they are reformed there, have not been identified. The temperature of the deep water of the Eurasian Basin has increased in the last 10 yr rather more than expected from geothermal heating. That geothermal heating does influence the deep water column was obvious from 2007 Polarstern observations made close to a hydrothermal vent in the Gakkel Ridge, where the temperature minimum usually found above the 600–800 m thick homogenous bottom layer was absent. However, heat entrained from the Atlantic water into descending, saline boundary plumes may also contribute to the warming of the deeper layers.
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33.
  • Schneider-Zapp, K., et al. (författare)
  • An automated gas exchange tank for determining gas transfer velocities in natural seawater samples
  • 2014
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 10:4, s. 587-600
  • Tidskriftsartikel (refereegranskat)abstract
    • In order to advance understanding of the role of seawater surfactants in the air-sea exchange of climatically active trace gases via suppression of the gas transfer velocity (k(w)), we constructed a fully automated, closed air-water gas exchange tank and coupled analytical system. The system allows water-side turbulence in the tank to be precisely controlled with an electronically operated baffle. Two coupled gas chromatographs and an integral equilibrator, connected to the tank in a continuous gas-tight system, allow temporal changes in the partial pressures of SF6, CH4 and N2O to be measured simultaneously in the tank water and headspace at multiple turbulence settings, during a typical experimental run of 3.25 h. PC software developed by the authors controls all operations and data acquisition, enabling the optimisation of experimental conditions with high reproducibility. The use of three gases allows three independent estimates of k(w) for each turbulence setting; these values are subsequently normalised to a constant Schmidt number for direct comparison. The normalised k(w) estimates show close agreement. Repeated experiments with Milli-Q water demonstrate a typical measurement accuracy of 4% for k(w). Experiments with natural seawater show that the system clearly resolves the effects on k(w) of spatial and temporal trends in natural surfactant activity. The system is an effective tool with which to probe the relationships between k(w), surfactant activity and biogeochemical indices of primary productivity, and should assist in providing valuable new insights into the air-sea gas exchange process.
  •  
34.
  • Sirevaag, A., et al. (författare)
  • Mixing, heat fluxes and heat content evolution of the Arctic Ocean mixed layer
  • 2011
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 7:3, s. 335-349
  • Tidskriftsartikel (refereegranskat)abstract
    • A comprehensive measurement program was conducted during 16 days of a 3 week long ice pack drift, from 15 August to 1 September 2008 in the central Amundsen Basin, Arctic Ocean. The data, sampled as part of the Arctic Summer Cloud Ocean Study (ASCOS), included upper ocean stratification, mixing and heat transfer as well as transmittance solar radiation through the ice. The observations give insight into the evolution of the upper layers of the Arctic Ocean in the transition period from melting to freezing. The ocean mixed layer was found to be heated from above and, for summer conditions, the net heat flux through the ice accounted for 22% of the observed change in mixed layer heat content. Heat was mixed downward within the mixed layer and a small, downward heat flux across the base of the mixed layer accounted for the accumulated heat in the upper cold halocline during the melting season. On average, the ocean mixed layer was cooled by an ocean heat flux at the ice/ocean interface (1.2 W m(-2)) and heated by solar radiation through the ice (-2.6 W m(-2)). An abrupt change in surface conditions halfway into the drift due to freezing and snowfall showed distinct signatures in the data set and allowed for inferences and comparisons to be made for cases of contrasting forcing conditions. Transmittance of solar radiation was reduced by 59% in the latter period. From hydro-graphic observations obtained earlier in the melting season, in the same region, we infer a total fresh water equivalent of 3.3 m accumulated in the upper ocean, which together with the observed saltier winter mixed layer indicates a transition towards a more seasonal ice cover in the Arctic.
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35.
  • Solomon, A., et al. (författare)
  • Freshwater in the Arctic Ocean 2010-2019
  • 2021
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 17:4, s. 1081-1102
  • Tidskriftsartikel (refereegranskat)abstract
    • U The Arctic climate system is rapidly transitioning into a new regime with a reduction in the extent of sea ice, enhanced mixing in the ocean and atmosphere, and thus enhanced coupling within the ocean-ice-atmosphere system; these physical changes are leading to ecosystem changes in the Arctic Ocean. In this review paper, we assess one of the critically important aspects of this new regime, the variability of Arctic freshwater, which plays a fundamental role in the Arctic climate system by impacting ocean stratification and sea ice formation or melt. Liquid and solid freshwater exports also affect the global climate system, notably by impacting the global ocean overturning circulation. We assess how freshwater budgets have changed relative to the 2000-2010 period. We include discussions of processes such as poleward atmospheric moisture transport, runoff from the Greenland Ice Sheet and Arctic glaciers, the role of snow on sea ice, and vertical redistribution. Notably, sea ice cover has become more seasonal and more mobile; the mass loss of the Greenland Ice Sheet increased in the 2010s (particularly in the western, northern, and southern regions) and imported warm, salty Atlantic waters have shoaled. During 2000-2010, the Arctic Oscillation and moisture transport into the Arctic are in-phase and have a positive trend. This cyclonic atmospheric circulation pattern forces reduced freshwater content on the Atlantic-Eurasian side of the Arctic Ocean and freshwater gains in the Beaufort Gyre. We show that the trend in Arctic freshwater content in the 2010s has stabilized relative to the 2000s, potentially due to an increased compensation between a freshening of the Beaufort Gyre and a reduction in freshwater in the rest of the Arctic Ocean. However, large intermodel spread across the ocean reanalyses and uncertainty in the observations used in this study prevent a definitive conclusion about the degree of this compensation.
  •  
36.
  • Staalstrom, A., et al. (författare)
  • Propagation and dissipation of internal tides in the Oslofjord
  • 2012
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 8:4, s. 525-543
  • Tidskriftsartikel (refereegranskat)abstract
    • Observations of velocity, pressure, temperature and salinity in the inner Oslofjord have been analysed to provide new information about the relationships between internal tides generated by tidal currents across the Drobak Sill and dissipation and diffusivity in the fjord. The most energetic vertical displacement of density surfaces inside the sill is associated with the first internal mode that has maximum amplitude around sill depth. The amplitude of the vertical displacement around sill depth correlates with the amplitude of the surface elevation, and, at a distance of 1 km inside the sill, the ratio between the amplitudes is 38, decreasing to 11 at a distance of 10 km. The greatest vertical displacements inside the sill, however, are found at 40 m depth. These latter internal waves are not associated with a first-mode internal tide, but are rather associated with higher internal modes controlled by stratification. The energy flux of the internal wave propagating from the Drobak Sill into the inner fjord on the east side of the Haoya Island is estimated to vary in the range 155-430 kW. This is the same order of magnitude as the estimated barotropic energy loss over the Drobak Sill (250 kW), but only 4-10% of the total barotropic flux. Approximately 40-70 % of the internal energy flux is lost within a distance of 10 km from the sill. The mean diffusivity below 90m depth in this area (similar to 20 cm(2) s(-1)) is more than four times higher than in the rest of the fjord (similar to 5 cm(2) s(-1) or less).
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37.
  • Stigebrandt, Anders, 1942, et al. (författare)
  • Consequences of artificial deepwater ventilation in the Bornholm Basin for oxygen conditions, cod reproduction and benthic biomass - a model study
  • 2015
  • Ingår i: Ocean Science. - 1812-0784 .- 1812-0792. ; 11:1, s. 93-110
  • Tidskriftsartikel (refereegranskat)abstract
    • We develop and use a circulation model to estimate hydrographical and ecological changes in the isolated basin water of the Bornholm Basin. By pumping welloxygenated so-called winter water to the greatest depth, where it is forced to mix with the resident water, the rate of deepwater density reduction increases as well as the frequency of intrusions of new oxygen-rich deepwater.We show that pumping 1000m3 s-1 should increase the rates of water exchange and oxygen supply by 2.5 and 3 times, respectively. The CRV (cod reproduction volume), the volume of water in the isolated basin meeting the requirements for successful cod reproduction (S > 11, O2 > 2mL L-1), should every year be greater than 54 km3, which is an immense improvement, since it has been much less in certain years. Anoxic bottoms should no longer occur in the basin, and hypoxic events will become rare. This should permit extensive colonization of fauna on the earlier periodically anoxic bottoms. Increased biomass of benthic fauna should also mean increased food supply to economically valuable demersal fish like cod and flatfish. In addition, re-oxygenation of the sediments should lead to increased phosphorus retention by the sediments.
  •  
38.
  • Stigebrandt, A., et al. (författare)
  • Consequences of artificial deepwater ventilation in the Bornholm Basin for oxygen conditions, cod reproduction and benthic biomass - a model study
  • 2015
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 11:1, s. 93-110
  • Tidskriftsartikel (refereegranskat)abstract
    • We develop and use a circulation model to estimate hydrographical and ecological changes in the isolated basin water of the Bornholm Basin. By pumping well-oxygenated so-called winter water to the greatest depth, where it is forced to mix with the resident water, the rate of deepwater density reduction increases as well as the frequency of intrusions of new oxygen-rich deepwater. We show that pumping 1000 m(3) s(-1) should increase the rates of water exchange and oxygen supply by 2.5 and 3 times, respectively. The CRV cod reproduction volume), the volume of water in the isolated basin meeting the requirements for successful cod reproduction (S > 11, O-2 > 2 mL L-1), should every year be greater than 54 km(3), which is an immense improvement, since it has been much less in certain years. Anoxic bottoms should no longer occur in the basin, and hypoxic events will become rare. This should permit extensive colonization of fauna on the earlier periodically anoxic bottoms. Increased biomass of benthic fauna should also mean increased food supply to economically valuable demersal fish like cod and flatfish. In addition, re-oxygenation of the sediments should lead to increased phosphorus retention by the sediments.
  •  
39.
  • Stranne, Christian, et al. (författare)
  • Acoustic mapping of mixed layer depth
  • 2018
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 14:3, s. 503-514
  • Tidskriftsartikel (refereegranskat)abstract
    • The ocean surface mixed layer is a nearly universal feature of the world oceans. Variations in the depth of the mixed layer (MLD) influences the exchange of heat, fresh water (through evaporation), and gases between the atmosphere and the ocean and constitutes one of the major factors controlling ocean primary production as it affects the vertical distribution of biological and chemical components in near-surface waters. Direct observations of the MLD are traditionally made by means of conductivity, temperature, and depth (CTD) casts. However, CTD instrument deployment limits the observation of temporal and spatial variability in the MLD. Here, we present an alternative method in which acoustic mapping of the MLD is done remotely by means of commercially available ship-mounted echo sounders. The method is shown to be highly accurate when the MLD is well defined and biological scattering does not dominate the acoustic returns. These prerequisites are often met in the open ocean and it is shown that the method is successful in 95% of data collected in the central Arctic Ocean. The primary advantages of acoustically mapping the MLD over CTD measurements are (1) considerably higher temporal and horizontal resolutions and (2) potentially larger spatial coverage.
  •  
40.
  • Tesi, Tommaso, et al. (författare)
  • Carbon geochemistry of plankton-dominated samples in the Laptev and East Siberian shelves : contrasts in suspended particle composition
  • 2017
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 13:5, s. 735-748
  • Tidskriftsartikel (refereegranskat)abstract
    • Recent Arctic studies suggest that sea ice decline and permafrost thawing will affect phytoplankton dynamics and stimulate heterotrophic communities. However, in what way the plankton composition will change as the warming proceeds remains elusive. Here we investigate the chemical signature of the plankton-dominated fraction of particulate organic matter (POM) collected along the Siberian Shelf. POM (>10 mu m) samples were analysed using molecular biomarkers (CuO oxidation and IP25 ) and dual-carbon isotopes (delta C-13 and Delta C-14). In addition, surface water chemical properties were integrated with the POM (>10 mu m) dataset to understand the link between plankton composition and environmental conditions. delta C-13 and Delta C-14 exhibited a large variability in the POM (> 10 mu m) distribution while the content of terrestrial biomarkers in the POM was negligible. In the Laptev Sea (LS), delta C-13 and Delta C-14 of POM (> 10 mu m) suggested a heterotrophic environment in which dissolved organic carbon (DOC) from the Lena River was the primary source of metabolisable carbon. Within the Lena plume, terrestrial DOC probably became part of the food web via bacteria uptake and subsequently transferred to relatively other heterotrophic communities (e.g. dinoflagellates). Moving eastwards toward the sea-ice-dominated East Siberian Sea (ESS), the system became progressively more autotrophic. Comparison between delta C-13 of POM (> 10 mu m) samples and CO(2)aq concentrations revealed that the carbon isotope fractionation increased moving towards the easternmost and most productive stations. In a warming scenario characterised by enhanced terrestrial DOC release (thawing permafrost) and progressive sea ice decline, heterotrophic conditions might persist in the LS while the nutrient-rich Pacific inflow will likely stimulate greater primary productivity in the ESS. The contrasting trophic conditions will result in a sharp gradient in delta C-13 between the LS and ESS, similar to what is documented in our semi-synoptic study.
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41.
  • Valk, Ole, et al. (författare)
  • Decrease in Th-230 in the Amundsen Basin since 2007 : far-field effect of increased scavenging on the shelf?
  • 2020
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 16:1, s. 221-234
  • Tidskriftsartikel (refereegranskat)abstract
    • This study provides dissolved and particulate Th-230 and Th-232 results as well as particulate( )(234)Th data collected during expeditions to the central Arctic Ocean (GEO-TRACES, an international project to identify processes and quantify fluxes that control the distributions of trace elements; sections GN04 and GIPY11). Constructing a time series of dissolved Th-230 from 1991 to 2015 enables the identification of processes that control the temporal development of Th-230 distributions in the Amundsen Basin. After 2007, Th-230 concentrations decreased significantly over the entire water column, particularly between 300 and 1500 m. This decrease is accompanied by a circulation change, evidenced by a concomitant increase in salinity. A potentially increased inflow of water of Atlantic origin with low dissolved Th-230 concentrations leads to the observed depletion in dissolved Th-230 in the central Arctic. Because atmospherically derived tracers (chlorofluorocarbon (CFC), sulfur hexafluoride (SF6)) do not reveal an increase in ventilation rate, it is suggested that these interior waters have undergone enhanced scavenging of Th during transit from Fram Strait and the Barents Sea to the central Amundsen Basin. The Th-230 depletion propagates downward in the water column by settling particles and reversible scavenging.
  •  
42.
  • Widdicombe, S., et al. (författare)
  • Unifying biological field observations to detect and compare oceanacidification impacts across marine species and ecosystems: what to monitorand why
  • 2023
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 19:1, s. 101-119
  • Tidskriftsartikel (refereegranskat)abstract
    • Approximately one-quarter of the CO2 emitted to the atmosphere annually from human activities is absorbed by the ocean, resulting in a reduction of seawater pH and shifts in seawater carbonate chemistry. This multi-decadal process, termed "anthropogenic ocean acidification " (OA), has been shown to have detrimental impacts on marine ecosystems. Recent years have seen a globally coordinated effort to measure the changes in seawater chemistry caused by OA, with best practices now available for these measurements. In contrast to these substantial advances in observing physicochemical changes due to OA, quantifying their biological consequences remains challenging, especially from in situ observations under real-world conditions. Results from 2 decades of controlled laboratory experiments on OA have given insight into the likely processes and mechanisms by which elevated CO2 levels affect biological process, but the manifestation of these process across a plethora of natural situations has yet to be fully explored. This challenge requires us to identify a set of fundamental biological and ecological indicators that are (i) relevant across all marine ecosystems, (ii) have a strongly demonstrated link to OA, and (iii) have implications for ocean health and the provision of ecosystem services with impacts on local marine management strategies and economies. This paper draws on the understanding of biological impacts provided by the wealth of previous experiments, as well as the findings of recent meta-analyses, to propose five broad classes of biological indicators that, when coupled with environmental observations including carbonate chemistry, would allow the rate and severity of biological change in response to OA to be observed and compared. These broad indicators are applicable to different ecological systems, and the methods for data analysis suggested here would allow researchers to combine biological response data across regional and global scales by correlating rates of biological change with the rate of change in carbonate chemistry parameters. Moreover, a method using laboratory observation to design an optimal observing strategy (frequency and duration) and observe meaningful biological rates of change highlights the factors that need to be considered when applying our proposed observation strategy. This innovative observing methodology allows inclusion of a wide diversity of marine ecosystems in regional and global assessments and has the potential to increase the contribution of OA observations from countries with developing OA science capacity.
  •  
43.
  • Zibordi, G., et al. (författare)
  • In situ determination of the remote sensing reflectance : an inter comparison
  • 2012
  • Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 8:4, s. 567-586
  • Tidskriftsartikel (refereegranskat)abstract
    • Inter-comparison of data products from simultaneous measurements performed with independent systems and methods is a viable approach to assess the consistency of data and additionally to investigate uncertainties. Within such a context the inter-comparison called Assessment of In Situ Radiometric Capabilities for Coastal Water Remote Sensing Applications (ARC) was carried out at the Acqua Alta Oceanographic Tower in the northern Adriatic Sea to explore the accuracy of in situ data products from various in- and above-water optical systems and methods. Measurements were performed under almost ideal conditions, including a stable deployment platform, clear sky, relatively low sun zenith angles and moderately low sea state. Additionally, all optical sensors involved in the experiment were inter-calibrated through absolute radiometric calibration performed with the same standards and methods. Inter-compared data products include spectral waterleaving radiance L-w(lambda), above-water downward irradiance E-d(0(+),lambda) and remote sensing reflectance R-rs(lambda). Data products from the various measurement systems/methods were directly compared to those from a single reference system/method. Results for R-rs(lambda) indicate spectrally averaged values of relative differences comprised between - 1 and +6 %, while spectrally averaged values of absolute differences vary from approximately 6% for the above-water systems/methods to 9 % for buoy-based systems/methods. The agreement between R-rs(lambda) spectral relative differences and estimates of combined uncertainties of the inter-compared systems/methods is noteworthy.
  •  
44.
  • Zielinski, Oliver, et al. (författare)
  • Detecting marine hazardous substances and organisms: sensors for pollutants, toxins, and pathogens
  • 2009
  • Ingår i: Ocean Science. - 1812-0784. ; 5:3, s. 329-349
  • Forskningsöversikt (refereegranskat)abstract
    • Marine environments are influenced by a wide diversity of anthropogenic and natural substances and organisms that may have adverse effects on human health and ecosystems. Real-time measurements of pollutants, toxins, and pathogens across a range of spatial scales are required to adequately monitor these hazards, manage the consequences, and to understand the processes governing their magnitude and distribution. Significant technological advancements have been made in recent years for the detection and analysis of such marine hazards. In particular, sensors deployed on a variety of mobile and fixed-point observing platforms provide a valuable means to assess hazards. In this review, we present state-of-the-art of sensor technology for the detection of harmful substances and organisms in the ocean. Sensors are classified by their adaptability to various platforms, addressing large, intermediate, or small areal scales. Current gaps and future demands are identified with an indication of the urgent need for new sensors to detect marine hazards at all scales in autonomous real-time mode. Progress in sensor technology is expected to depend on the development of small-scale sensor technologies with a high sensitivity and specificity towards target analytes or organisms. However, deployable systems must comply with platform requirements as these interconnect the three areal scales. Future developments will include the integration of existing methods into complex and operational sensing systems for a comprehensive strategy for long-term monitoring. The combination of sensor techniques on all scales will remain crucial for the demand of large spatial and temporal coverage.
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