| 1. |
- Wahlstrom, I., et al.
(författare)
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Projected climate change impact on a coastal sea-As significant as all current pressures combined
- 2022
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 28:17, s. 5310-5319
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Tidskriftsartikel (refereegranskat)abstract
- Climate change influences the ocean's physical and biogeochemical conditions, causing additional pressures on marine environments and ecosystems, now and in the future. Such changes occur in environments that already today suffer under pressures from, for example, eutrophication, pollution, shipping, and more. We demonstrate how to implement climate change into regional marine spatial planning by introducing data of future temperature, salinity, and sea ice cover from regional ocean climate model projections to an existing cumulative impact model. This makes it possible to assess climate change impact in relation to pre-existing cumulative impact from current human activities. Results indicate that end-of-century projected climate change alone is a threat of the same magnitude as the combination of all current pressures to the marine environment. These findings give marine planners and policymakers forewarning on how future climate change may impact marine ecosystems, across space, emission scenarios, and in relation to other pressures.
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| 2. |
- Muchowski, Julia, 1989-, et al.
(författare)
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Diapycnal Mixing Induced by Rough Small-Scale Bathymetry
- 2023
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 50:13
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Tidskriftsartikel (refereegranskat)abstract
- Diapycnal mixing impacts vertical transport rates of salt, heat, and other dissolved substances, essential for the overturning circulation and ecosystem functioning in marine systems. While most studies have focused on mixing induced by individual obstacles in tidal flows, we investigate the net effect of non-tidal flow over multiple small-scale (<1 km) bathymetric features penetrating a strongly-stratified density interface in a coastal region. We combine high-resolution broadband acoustic observations of turbulence microstructure with traditional shear microstructure profiling, to resolve the variability and intermittency of stratified turbulence related to the rough bathymetry. Scale analysis and acoustic imaging suggest that underlying mixing mechanisms are related to topographic wake eddies and breaking internal waves. Depth averaged dissipation rates (1.1 × 10−7 Wkg−1) and turbulent vertical diffusivities (7 × 10−4 m2s−1) in the halocline exceed reference values by two orders of magnitude. Our study emphasizes the importance of rough small-scale bathymetric features for the vertical transport of salt in coastal areas.
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| 3. |
- Arneborg, Lars, 1969, et al.
(författare)
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Gravity Current Dynamics and Entrainment - A Process Study Based on Observations in the Arkona Basin
- 2007
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Ingår i: journal of physical oceanography. ; 37, s. 2094-2113
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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.
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| 4. |
- Burchard, H., et al.
(författare)
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Dynamics of medium-intensity dense water plumes in the Arkona Basin, Western Baltic Sea
- 2005
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Ingår i: Ocean Dynamics. - : Springer Science and Business Media LLC. - 1616-7341 .- 1616-7228. ; 55:5-6, s. 391-402
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the dynamics of medium-intensity inflow events over Drogden Sill into the Arkona Sea are investigated. Idealised model simulations carried out with the General Estuarine Transport Model suggest that most of the salt transport during such inflow events occur north of Kriegers Flak, a shoal with less than 20 in water depth Surrounded by water depths of more than 40 in. This assumption about the pathway is supported by recent ship-based observations in the Arkona Sea during a medium-intensity inflow event. The propagation of a saline bottom plume could be observed during several days after having passed Drogden Sill. In the area north of Kriegers Flak the plume was about 10 m thick, and propagated with more than 0.5 m s(-1) and a salinity of tip to 20 psu (with ambient water salinity being 8 psu) eastwards. Although the model simulations were idealised, the Structural agreement between the observation and model result was good, The structure and pathways of these medium-intensity inflow events are of specific interest due to the plans for erecting extensive offshore wind farms in the Arkona Sea which may under certain circumstances lead to increased entrainment of ambient water into the bottom Plumes.
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| 5. |
- Muhlemann, B., et al.
(författare)
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Ancient human parvovirus B19 in Eurasia reveals its long-term association with humans
- 2018
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 115:29, s. 7557-7562
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Tidskriftsartikel (refereegranskat)abstract
- Human parvovirus B19 (B19V) is a ubiquitous human pathogen associated with a number of conditions, such as fifth disease in children and arthritis and arthralgias in adults. B19V is thought to evolve exceptionally rapidly among DNA viruses, with substitution rates previously estimated to be closer to those typical of RNA viruses. On the basis of genetic sequences up to similar to 70 years of age, the most recent common ancestor of all B19V has been dated to the early 1800s, and it has been suggested that genotype 1, the most common B19V genotype, only started circulating in the 1960s. Here we present 10 genomes (63.9-99.7% genome coverage) of B19V from dental and skeletal remains of individuals who lived in Eurasia and Greenland from similar to 0.5 to similar to 6.9 thousand years ago (kya). In a phylogenetic analysis, five of the ancient B19V sequences fall within or basal to the modern genotype 1, and five fall basal to genotype 2, showing a long-term association of B19V with humans. The most recent common ancestor of all B19V is placed similar to 12.6 kya, and we find a substitution rate that is an order of magnitude lower than inferred previously. Further, we are able to date the recombination event between genotypes 1 and 3 that formed genotype 2 to similar to 5.0-6.8 kya. This study emphasizes the importance of ancient viral sequences for our understanding of virus evolution and phylogenetics.
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| 6. |
- Selander, Erik, 1973, et al.
(författare)
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Chemical signaling in the turbulent ocean-hide and seek at the Kolmogorov scale
- 2020
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Ingår i: Fluids. - : MDPI AG. - 2311-5521. ; 5:2
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Tidskriftsartikel (refereegranskat)abstract
- Chemical cues and signals mediate resource acquisition, mate finding, and the assessment of predation risk in marine plankton. Here, we use the chemical properties of the first identified chemical cues from zooplankton together with in situ measurements of turbulent dissipation rates to calculate the effect of turbulence on the distribution of cues behind swimmers as well as steady state background concentrations in surrounding water. We further show that common zooplankton (copepods) appears to optimize mate finding by aggregating at the surface in calm conditions when turbulence do not prevent trail following. This near surface environment is characterized by anisotropic turbulence and we show, using direct numerical simulations, that chemical cues distribute more in the horizontal plane than vertically in these conditions. Zooplankton may consequently benefit from adopting specific search strategies near the surface as well as in strong stratification where similar flow fields develop. Steady state concentrations, where exudation is balanced by degradation develops in a time scale of ~5 h. We conclude that the trails behind millimeter-sized copepods can be detected in naturally occurring turbulence below the wind mixed surface layer or in the absence of strong wind. The trails, however, shorten dramatically at high turbulent dissipation rates, above ~10−3 cm2 s−3 (10−7 W kg−1). © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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| 7. |
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| 8. |
- Umlauf, L., et al.
(författare)
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Dynamics of rotating shallow gravity currents passing through a channel. Part I: Observation of transverse structure
- 2009
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Ingår i: Journal of Physical Oceanography. ; 39, s. 2385-2401
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Tidskriftsartikel (refereegranskat)abstract
- We present a detailed data set describing a quasi-stationary bottom gravity current, approximately 10 m thick and 10 km wide, passing through a channel-like constriction in the Western Baltic Sea. The data include full-depth, synoptic, and highly resolved transects of stratification and turbulence parameters, as well as detailed velocity transects across the gravity current at different down-channel locations. Our velocity data reveal a persistent transverse circulation, creating a characteristic wedge-shaped density structure in the interface. A strong asymmetry was also found in the interior of the gravity current, where we observed the evolution of a dynamically significant transverse density gradient to the right of the down-channel flow. Spectral analysis of the near-bottom velocities showed a surprisingly strong contribution to the bottom stress from low-frequency motions with periods up to 30 minutes that are possibly related to internal wave effects. Cross-channel transects of shearmicrostructure were used to investigate the transverse variation of local entrainment rates and bottom stresses. These data indicate that frictional control is essential for this class of gravity currents that are characterized by subcritical Froude numbers, small entrainment, strong rotational effects, and small thickness compared to the bottom Ekman layer.
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| 9. |
- Umlauf, L., et al.
(författare)
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Dynamics of rotating shallow gravity currents passing through a channel. Part II: Analysis
- 2009
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Ingår i: Journal of Physical Oceanography. ; 39, s. 2402-2416
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Tidskriftsartikel (refereegranskat)abstract
- The physics of frictional control for channelized rotating gravity currents are analyzed using an extensive data set including hydrographic, current, and microstructure measurements from the Western Baltic Sea. Rotational effects in these gravity currents, characterized by Ekman numbers of the order of one and sub-critical Froude numbers, induce a complex transverse circulation that strongly affects the internal dynamics. The key component of this circulation is a geostrophically balanced transverse jet in the interface that modifies the entrainment process by (i) laterally draining the interface and (ii) providing additional interfacial shear comparable to the down-channel shear. The recirculation of mixed interfacial fluid into the interior distorts the internal density structure of the gravity current, and creates a thermal wind shear in the interior that is comparable to the observed shear. Using a theoretical model, this effect is shown to be responsible for the three-layer structure of the transverse velocity with the near-bottom velocity and stress directed opposite to the Ekman transport. Our analysis confirms the key assumption in available models for frictional control in rotating gravity currents: the transverse Ekman transport is balanced by the geostrophic transport due to the down-channel tilt of the interface.
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| 10. |
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