| 1. |
- Amir Heidari, Payam, 1989, et al.
(författare)
-
A state-of-the-art model for spatial and stochastic oil spill risk assessment: A case study of oil spill from a shipwreck
- 2019
-
Ingår i: Environment International. - : Elsevier BV. - 0160-4120 .- 1873-6750. ; 126, s. 309-320
-
Tidskriftsartikel (refereegranskat)abstract
- Oil spills are serious environmental issues that potentially can cause adverse effects on marine ecosystems. In some marine areas, like the Baltic Sea, there is a large number of wrecks from the first half of the 20th century, and recent monitoring and field work have revealed release of oil from some of these wrecks. The risk posed by a wreck is governed by its condition, hazardous substances contained in the wreck and the state of the surrounding environment. Therefore, there is a need for a common standard method for estimating the risks associated with different wrecks. In this work a state-of-the-art model is presented for spatial and stochastic risk assessment of oil spills from wrecks, enabling a structured approach to include the complex factors affecting the risk values. A unique feature of this model is its specific focus on uncertainty, facilitating probabilistic calculation of the total risk as the integral expected sum of many possible consequences. A case study is performed in Kattegat at the entrance region to the Baltic Sea to map the risk from a wreck near Sweden. The developed model can be used for oil spill risk assessment in the marine environment all over the world.
|
|
| 2. |
- Olofsson, Malin, et al.
(författare)
-
Nitrate and ammonium fluxes to diatoms and dinoflagellates at a single cell level in mixed field communities in the sea
- 2019
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- Growth of large phytoplankton is considered to be diffusion limited at low nutrient concentrations, yet their constraints and contributions to carbon (C) and nitrogen fluxes in field plankton communities are poorly quantified under this condition. Using secondary ion mass spectrometry (SIMS), we quantified cell-specific assimilation rates of C, nitrate, and ammonium in summer communities of large phytoplankton when dissolved inorganic nitrogen concentrations are low in temperate coastal regions. Chain-forming diatoms composed 6% of total particulate organic carbon, but contributed 20% of C assimilation, 54% of nitrate assimilation and 32% of ammonium assimilation within the plankton community. In contrast, large dinoflagellates composed 11% of total POC, and contributed 14% of the C assimilation, 4% of ammonium and 9% of nitrate assimilation within the plankton community. Measured cell-specific C and nitrate assimilation rate match the Redfield ratio and the maximal nitrate assimilation in Chaetoceros spp. predicted by mass transfer theory. However, average ammonium assimilation rates were 30 and 340% higher than predicted by mass transfer theory in Tripos/Ceratium and Chaetoceros, respectively, suggesting that microbial interactions in the phycosphere may facilitate substantial luxury ammonium uptake by Chaetoceros in environments with fluctuating nitrate concentrations.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Arneborg, Lars, 1969, et al.
(författare)
-
Gravity Current Dynamics and Entrainment - A Process Study Based on Observations in the Arkona Basin
- 2007
-
Ingår i: journal of physical oceanography. ; 37, s. 2094-2113
-
Tidskriftsartikel (refereegranskat)abstract
- A 19 hour time series of dissipation, stratification and horizontal velocities has been obtained for a dense gravity current flowing into the Arkona Basin in the western Baltic Sea. The observations are compared with one-dimensional, quasi-steady theory, where the gravity component in the flow direction is balanced by bottom friction, while that in the cross flow direction is balanced by the Coriolis force. The observations deviate from the theory in that the bottom shear stress is more than twice as large as that required to balance the gravity. Several reasons for this discrepancy are discussed. A 1D turbulence model is also compared with the observations. Profiles of velocity, stratification and dissipation rates generally show similar variations with depth as the observations, although the observed dissipation rates are somewhat larger than the modeled and the modeled transverse velocities are much larger than the observed. Subsequently, the model is used to investigate the variation of the entrainment parameter for a large range of Ekman and Froude numbers. Within the modeled parameter space, the entrainment parameter can be collapsed onto a curve that is an increasing function of both the Froude and the Ekman numbers. There is one puzzling result of the observations that differs from the model results and earlier observations, namely that the observed entrainment rate increases dramatically during the observation period, where the Froude number decreases slightly. Some reasons for this increase are discussed.
|
|
| 6. |
- Arneborg, Lars, 1969, et al.
(författare)
-
MIXING IN FJORDS AND THE RELATION BETWEEN LOCAL ENERGY DISSIPATION AT A FJORD SILL AND RADIATED INTERNAL TIDES
- 2012
-
Ingår i: TOS/ASLO/AGU 2012 Ocean Science Meeting abstract book, Salt Lake City, USA.
-
Konferensbidrag (refereegranskat)abstract
- Diapycnal mixing in a sill fjord is vital for renewal of the deep water inside the sill. Tides can cause such mixing, both by local turbulence at the sill associated with supercritical baroclinic flow and internal hydraulic jumps, and by radiation of internal tides away from the sill that dissipate elsewhere and cause turbulence and mixing there. Previous studies tend to look at these two processes as independent of each others, whereas they in reality are closely linked: The internal tide generation depends on the hydraulic conditions at the fjord sill, and the internal hydraulic jump strength depends on the upstream and downstream radiated columnar disturbances which over time constitute the internal tides. An effort is done to link the hydraulic theory and the internal tide generation theory, and the result is compared to recent intensive observations over the Oslo fjord sill, including high-resolution microstructure profiler transects and mooring data on and inside the sill.
|
|
| 7. |
- Arneborg, Lars, 1969, et al.
(författare)
-
Overturning and Dissipation caused by Baroclinic Tidal Flow near the Sill of a Fjord Basin
- 2009
-
Ingår i: Journal of Physical Oceanography. ; 39, s. 2156-2174
-
Tidskriftsartikel (refereegranskat)abstract
- Dissipation time series and moored velocity and density time series on the inner slopes of the Gullmar Fjord sill, showed that the internal tides generated at the sill radiated to the head of the fjord, were reflected, and radiated back to the sill, where they dissipated their energy mainly below sill level. A large amount of the dissipation was caused by a transitional flow at a particular phase of the internal tide, when the bottom layer descended down the sill slope and had to pass a constriction set up by a submarine hill. The inward, baroclinic, bottom layer flow transformed into a supercritical bottom jet, which separated from the bottom just downstream of the constriction. A large fraction of the dissipation took place in the successive rebounding region (the hydraulic jump) above the bottom jet, where overturns of the same size as the vertical extent of the rebounding region were observed. More than half of the dissipation was happening in the bottom boundary layer below the jet. During the transitional flow there were clear pulsations of the jet with periods of about 15 min. The amount of diapycnal mixing caused by the turbulence was reduced by the large fraction of dissipation within the bottom boundary layer, but maybe also by the high buoyancy Reynolds numbers within the rebounding region. When using a relatively new parameterization of mixing, the mixing was significantly reduced compared to using the traditional constant mixing efficiency method.
|
|
| 8. |
- Arneborg, Lars, 1969, et al.
(författare)
-
Persistent inflow of warm water onto the central Amundsen Shelf
- 2012
-
Ingår i: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 5:12, s. 876-880
-
Tidskriftsartikel (refereegranskat)abstract
- The West Antarctic Ice Sheet contains enough ice to raise global sea level by several metres and, because it is grounded mainly below sea level, it is sensitive to ocean warming 1 . Accelerated thinning of glaciers that discharge into the Amundsen Sea over the past decades 2–4 has been proposed to be related to the presence of warmer waters beneath the ice shelves 4–6 . Three deep troughs crosscut the continental shelf of the Amundsen Sea, forming passages through which warm ocean waters can access the ice shelves, but oceanographic data has been limited. Here we present direct measurements from an ocean mooring and ship transect of the temperatures, salinities and velocities from one of these troughs in the central Amundsen Sea during the year 2010. The data show persistent inflow towards the ice shelf of relatively warm and salty water at the bottom of the trough throughout the year, and outflow of colder water above. Superposed on this background flow are barotropic current fluctuations that do not contribute significantly to the overall transport. In contrast to numerical models 7,8 , which show seasonal inflow changes in response to regional winds, we find that warm water is supplied to the Central Amundsen Shelf without strong seasonal variability.
|
|
| 9. |
- Arneborg, Lars, 1969, et al.
(författare)
-
Spatial variability of diapycnal mixing and turbulent dissipation rates in a stagnant fjord basin
- 2004
-
Ingår i: Journal of Physical Oceanography. - 0022-3670. ; 34:7, s. 1679-1691
-
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.
|
|
| 10. |
- Arneborg, Lars, 1969, et al.
(författare)
-
Strömklimat vid två potentiella testbäddar för strömenergi vid Orust
- 2015
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Strömmätningar har utförts vid två positioner utanför Orust som ligger i Fyrbodalsområdet, för att skapa underlag för diskussioner om möjligheter och fördelar med etablering av en testbädd för marin strömenergi i Sverige. Båda positionerna uppfyller en stor del av önskemålen från Minesto, Sveriges mest etablerade företag för utvinning av el ur havsströmmar. Den ena, utanför Måseskär, är en relativt oskyddad position med ganska kraftiga strömmar nära ytan. Strömmarna är relativt variabla på tidsskalor från några dygn till veckor. Den andra, vid Svanesund innanför Orust, är en skyddad position dominerad av tidvattenrörelser. Variationerna i tiden är därför stora, med riktningsändringar fyra gånger per dygn, men dessa är förutsägbara, och variationerna över djupet är små. Däremot är fjordarna innanför Svanesund känsliga för strömhastigheter och vattentransporter genom sundet, vilka kommer att påverkas av strömenergietableringar. En testbädd där kräver därför miljökonsekvensanalyser för att undersöka hur stort energiuttag som kan göras utan att försämra fjordmiljön.
|
|
