| 1. |
- Andersson, Helén C., 1968, et al.
(författare)
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Regulation of the Indonesian throughflow by baroclinic draining of the North Australian Basin
- 2005
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Ingår i: Deep-Sea Research Part I-Oceanographic Research Papers. - : Elsevier BV. - 0967-0637. ; 52:12, s. 2214-2233
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Tidskriftsartikel (refereegranskat)abstract
- The Indonesian throughflow (ITF) is studied using historic hydrographical data with purpose of obtaining a description of the characteristics of the large-scale flow and an understanding of both the forcing and control of the flow. The investigation makes use of the steric sea level and the contents of freshwater and heat in the water Column integrated down to the depth of the deepest connection (effective sill depth) between the Pacific and Indian Oceans within the Indonesian seas. It is shown that it is mainly low-saline water of North Pacific origin that fills the upper part of both the Indonesian seas and a downstream buoyant (surface) pool (DBP) that stretches horizontally over a large part of the North Australian Basin. The long-term mean steric sea level in the Indonesian seas is approximately horizontal and equal to the sea level in the neighboring part of the Pacific Ocean. This indicates small frictional losses against the mean throughflow, which is verified using a coupled multiple basin model of the Indonesian seas. The chan e of the steric sea level, from the Pacific Ocean level to the Indian Ocean level, Occurs essentially at the border between the DBP and the adjacent Indian Ocean. It is found that Darwin is situated inside the DBP, indicating that the sea level recorded in this place is a poor representative of mean and low frequency parts of the sea level variability of the Indian Ocean. It is argued that the control of ITF is set by the baroclinic transport capacity of the DBP relative to the adjacent (Indian Ocean) water. The mean ITF, estimated as the Outflow from the DBP to the South Equatorial Current, is about 10 Sv. The integrated ITF imprint is fresh and cold and the net heat transport is estimated to be 0.3 PW. The buffering capacity of the DBP is about 5 years, so variations in the circulation should be modest on shorter time-scales. It is suggested that the atmospheric transfer of freshwater to the North Pacific and vertical mixing in the North Pacific provide the driving of the mean ITF and that ITF is a major branch of the estuarine-type vertical circulation of the North Pacific. (c) 2005 Elsevier Ltd. All rights reserved.
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| 2. |
- Arneborg, Lars, 1969, et al.
(författare)
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Spatial variability of diapycnal mixing and turbulent dissipation rates in a stagnant fjord basin
- 2004
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Ingår i: Journal of Physical Oceanography. - 0022-3670. ; 34:7, s. 1679-1691
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Tidskriftsartikel (refereegranskat)abstract
- Two microstructure profilers, two ships, and four moorings with acoustic Doppler current profilers and conductivity-temperature loggers were used in an intensive effort to map the spatial and temporal variations of vertical mixing in the stagnant deep basin of Gullmar Fjord, Sweden. During three days in the beginning of August 2001 a continuous time series of turbulent kinetic energy dissipation profiles was obtained with one microstructure profiler at a fixed position near the deepest part of the fjord. During the same period the other microstructure profiler was used to obtain six sections of dissipation through the length of the basin. Two moorings were deployed in the fjord basin for one month from the end of July to the end of August. The mapping of dissipation rates reveals that the dissipation in the deep basin is confined to areas just inside the sill. More than 77% of the dissipation in the fjord basin happens above the sloping bottoms closest to the sill.
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| 3. |
- Arneborg, Lars, 1969, et al.
(författare)
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The rate of inflow and mixing during deep-water renewal in a sill fjord
- 2004
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Ingår i: Limnology and Oceanography. - 0024-3590. ; 49:3, s. 768-777
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Tidskriftsartikel (refereegranskat)abstract
- We obtained high-resolution data on a deep-water renewal in the basin of Gullmar Fjord, Sweden, using an autonomous profiling platform. In the middle of the fjord, where the platform is anchored, renewal starts with the passage of a gravity current front and continues with a steady thickening of the new, oxygen-rich, low-nitrate bottom layer and an associated lifting of the old, oxygen-depleted, high-nitrate bottom water. The basin continuously fills to sill level during a period of 10 d. At the mouth of the fjord, a three-layer structure develops. Renewal is driven by the density difference between the intermediate water inside and the new deep water outside the fjord. The volume flux is well predicted by a hydraulic exchange model in which the upper layer plays a passive role. Local upwelling and downwelling of the upper halocline cause fluctuating baroclinic currents during renewal, but these seem to have little influence on the average volume flux of new deep water. Entrainment rates are small, and the associated volume flux increase seems to be balanced by detrainment.
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| 4. |
- Axelsson, Lars-Olof, et al.
(författare)
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Hur mycket torsk konsumerar mellanskarv i Byfjorden?
- 2021
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Ingår i: VATTEN - Journal of Water Management and Research. ; 77:2, s. 105-114
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Vi har mätt längden av otoliter från torsk i 76 spybollar från mellanskarv (Phalacrocorax carbo sinensis), insamlade från ön Ringburen i Byfjorden vilken ingår i fjordsystemet mellan Orust och fastlandet. Genom att använda en matematisk formel, vilken härleds i denna uppsats, har vi fastställt vikten av varje konsumerad torsk. Med antagandet att 10 – 25 skarvar som årsgenomsnitt försörjer sig i Byfjorden kommer vi fram till ett årligt torskuttag i intervallet 1400 - 3400 kg fördelat på mellan 18000 – 44000 individer varav 90 – 220 är lekmogna. Detta skulle kunna påverka den lokala rekryteringen av torsk och motverka förväntade positiva effekter av nyligen utlagda artificiella rev. Det saknas uppskattningar av torskbeståndets storlek och dess fördelning på olika storleksklasser samt årlig rekrytering och tillväxttakt varför man inte nu kan bedöma effekten av skarvarnas predation på torskbeståndet i Byfjorden och fjordsystemet. En matematisk modell av torskbeståndet i fjordsystemet kan bidra till att strukturera problemet samt även leverera prognoser under olika antaganden.
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| 5. |
- Bonaglia, Stefano, 1983, et al.
(författare)
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High methane emissions from an anoxic fjord driven by mixing and oxygenation : High methane emissions from fjords
- 2022
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Ingår i: Limnology and Oceanography Letters. - : Wiley. - 2378-2242. ; 7:5, s. 392-400
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Tidskriftsartikel (refereegranskat)abstract
- Oceanic methane (CH4) budgets lack data from high-latitude fjords that often behave as intermittently anoxic ecosystems with potentially high methane emissions. We conducted 15 expeditions and 49 in situ lander deployments in an anoxic Scandinavian fjord between 2009 and 2021. Benthic fluxes were highest at the deepest anoxic site (average 516μmol CH4 m−2 d−1), supporting bottom water methane exceeding 5000nM. Natural and engineered mixing events displaced methane-rich bottom waters, enhancing upper water concentrations and driving high sea–air flux reaching 641μmol CH4 m−2 d−1. Mixing also reduced pelagic methane oxidation from 70% to 20% of all methane sources into the fjord. Upscaling of literature fluxes combined with our results suggests that fjords globally emit 1.0±0.8 Tg CH4 yr−1. Despite their small global area, fjords are hotspots of methane release. We suggest that ongoing deoxygenation and global change will enhance methane emissions from fjords.
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| 6. |
- Chen, Deliang, 1961, et al.
(författare)
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Summary of a workshop on extreme weather events in a warming world organized by the Royal Swedish Academy of Sciences
- 2020
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Ingår i: Tellus Series B-Chemical and Physical Meteorology. - : Stockholm University Press. - 1600-0889 .- 0280-6509. ; 72:1
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is not only about changes in means of climatic variables such as temperature, precipitation and wind, but also their extreme values which are of critical importance to human society and ecosystems. To inspire the Swedish climate research community and to promote assessments of international research on past and future changes in extreme weather events against the global climate change background, the Earth Science Class of the Royal Swedish Academy of Sciences organized a workshop entitled 'Extreme weather events in a warming world' in 2019. This article summarizes and synthesizes the key points from the presentations and discussions of the workshop on changes in floods, droughts, heat waves, as well as on tropical cyclones and extratropical storms. In addition to reviewing past achievements in these research fields and identifying research gaps with a focus on Sweden, future challenges and opportunities for the Swedish climate research community are highlighted.
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| 7. |
- Colliander Celik, Å, et al.
(författare)
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Därför krävs det stora satsningar på geografi och geovetenskap
- 2021
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Ingår i: Läraren. - 1101-2633.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Som geografer, geovetare och geografilärare frågar vi oss varför kunskaper om vår livsmiljö, och de processer som styr den, är så styvmoderligt behandlade i skolan när vårt samhälle och stora delar av vår civilisation står inför många stora utmaningar, skriver 52 tunga företrädare.
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| 8. |
- De Brabandere, L., et al.
(författare)
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Oxygenation of an anoxic fjord basin strongly stimulates benthic denitrification and DNRA
- 2015
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Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 126:1, s. 131-152
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Tidskriftsartikel (refereegranskat)abstract
- © 2015 Springer International Publishing Switzerland Hypoxia hampers eutrophication reduction efforts by enabling high nutrient fluxes from sediment to bottom waters. Oxygenation of hypoxic water bodies is often proposed to reduce benthic ammonium and phosphate release. This study investigates the functional response of benthic nitrate-reducing processes to a long-term engineered oxygenation effort in a density-stratified fjord with euxinic bottom waters. Oxygenation was achieved by mixing surface water with deep, euxinic water, which increased oxygen and nitrate concentrations in the deep water column. The presence of nitrate instigated benthic nitrate reduction in the newly oxidized sediments by equally stimulating denitrification and dissimilatory nitrate reduction to ammonium (DNRA). DNRA and total nitrate reduction rates, as well as the contribution of DNRA to total nitrate reduction, decreased with increasing exposure time of the sediments to oxygen. The relative importance of DNRA as a nitrate sink was correlated to nitrate concentrations, with more nitrate being reduced to ammonium at higher bottom water nitrate concentrations. Overall, engineered oxygenation decreased the net efflux of dissolved inorganic nitrogen from the sediments by stimulating net nitrate removal through denitrification.
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| 9. |
- Erlandsson, Carina P., et al.
(författare)
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Increased utility of the Secchi disk to assess eutrophication in coastal waters with freshwater run-off
- 2006
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963. ; 60:1-2, s. 19-29
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Tidskriftsartikel (refereegranskat)abstract
- Changed local Supply of nutrients in coastal waters can lead to changed content of phytoplankton. This influences the visibility, and thereby the water quality in the surface layers, which can be observed by e.g., the Secchi disk. However, the translation of Secchi depth observations to plankton content is complicated by the existence of light attenuating matter entering with run-off from land. To increase the utility of Secchi depth measurements to assess local eutrophication in coastal waters, a formula for calculating the Secchi depth in areas influenced by freshwater was developed. The study includes data analysis of Seechi depth, chlorophyll content, wind speed, and freshwater height estimated from salinity at two stations in the Gullmar Fjord in Sweden. The correlation coefficient between calculated and observed Secchi depths at the inner station close to the freshwater source increased from 0.63 using chlorophyll as the only dependent parameter, to 0.75 (p < 0.001) including the accumulated freshwater in the surface layer from run off, and wind speed. At the outer station close to the mouth of the fjord it increased from 0.68 to 0.70 (p < 0.001) The correlation between observed and calculated Secchi depth decreased considerably, if the restriction to observations made at sun elevations higher than about 30 degrees above the horizon was relaxed. (c) 2005 Elsevier B.V. All rights reserved.
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| 10. |
- Erlandsson, Carina P., et al.
(författare)
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The sensitivity of minimum oxygen concentrations in a fjord to changes in biotic and abiotic external forcing
- 2006
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Ingår i: Limnology and Oceanography. - 0024-3590. ; 51:1, part 2, s. 631-638
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the possible biotic and abiotic causes of the observed long-term decrease of oxygen minimum concentrations in the deep water of Gullmar Fjord. Physical factors explained about 40% of the decreased minimum oxygen concentrations since the 1950s. The North Atlantic Oscillation and more regional climate variations account for an important part of this change. The effect of the climate variations was mainly on the timing of the renewal of the basin water. The consumption rate of oxygen in the basin water has increased by 50% since the 1950s. This biotic effect explained about 60% of the decrease in minimum oxygen concentrations. The likely dominating source of oxygen-consuming matter was (remote) production in the Skagerrak, suggesting that there has been a long-term increase of particulate organic carbon in the Skagerrak water.
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