| 1. |
- Carlsson, Björn, 1980-, et al.
(författare)
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Evaluation of a roughness length model and sea surface properties with data from the Baltic Sea
- 2010
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Ingår i: Journal of Physical Oceanography. - 0022-3670 .- 1520-0485. ; 40:9, s. 2007-2024
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Tidskriftsartikel (refereegranskat)abstract
- The exchange of momentum between the oceans and atmosphere is important for many atmospheric and oceanic processes and is mainly governed by the roughness of sea surface. The roughness can be expressed by a roughness length z0. A roughness length model, based on the concept that z0 is determined by stochastic wave breaking, is presented. The model performance is evaluated using measurements from the Östergarnsholm site, in the Baltic Sea, and pertinent information from other recent investigations. The wave field and the roughness length variations are investigated during various sea state conditions dominated by wind-driven waves. It is found that several parameters, describing the characteristics of the wave field, are dependent on the amount of energy that long waves have relative to the energy of short, wind-driven waves of the sea spectrum (called the swell ratio). The impact of swell ratio on z0 can explain the discrepancies found in various results among relevant investigations. The roughness length model can well reproduce the observed roughness length.
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| 2. |
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| 3. |
- Meier, Markus, et al.
(författare)
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An Earth System Science Program for the Baltic Sea Region
- 2014
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Ingår i: EOS. - 0096-3941 .- 2324-9250. ; 95:13, s. 109-110
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Tidskriftsartikel (refereegranskat)abstract
- From Russia in the east to Sweden, Denmark, and Germany in the west, reaching south to the tips of the Czech Republic, Slovakia, and Ukraine, the Baltic Sea watershed drains nearly 20% of Europe (see Figure 1). In the highly populated south, the temperate climate hosts intensive agriculture and industry. In the north, the landscape is boreal and rural. In the Baltic Sea itself, complex bathymetry and stratification patterns as well as extended hypoxic and anoxic deep waters add to the diversity. Yet in recent history, the differences across the Baltic Sea region have been more than physical: In the mid-20th century, the watershed was split in two.
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| 4. |
- Omstedt, Anders, 1949, et al.
(författare)
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Future changes in the Baltic Sea acid-base (pH) and oxygen balances
- 2012
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Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 64
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Tidskriftsartikel (refereegranskat)abstract
- Possible future changes in Baltic Sea acid–base (pH) and oxygen balances were studied using a catchment–sea coupled model system and numerical experiments based on meteorological and hydrological forcing datasets and scenarios. By using objective statistical methods, climate runs for present climate conditions were examined and evaluated using Baltic Sea modelling. The results indicate that increased nutrient loads will not inhibit future Baltic Sea acidification; instead, the seasonal pH cycle will be amplified by increased biological production and mineralization. All examined scenarios indicate future acidification of the whole Baltic Sea that is insensitive to the chosen global climate model. The main factor controlling the direction and magnitude of future pH changes is atmospheric CO2 concentration (i.e. emissions). Climate change and land-derived changes (e.g. nutrient loads) affect acidification mainly by altering the seasonal cycle and deep-water conditions. Apart from decreasing pH, we also project a decreased saturation state of calcium carbonate, decreased respiration index, and increasing hypoxic area – all factors that will threaten the marine ecosystem. We demonstrate that substantial reductions in fossil-fuel burning are needed to minimize the coming pH decrease and substantial reductions in nutrient loads are needed to reduce the coming increase in hypoxic and anoxic waters.
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| 5. |
- Rutgersson, Anna, 1971-, et al.
(författare)
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Enhancement of CO2 transfer velocity due to water-side convection
- 2010
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963 .- 1879-1573. ; 80:1-2, s. 125-134
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Tidskriftsartikel (refereegranskat)abstract
- The exchange of CO2 between ocean and atmosphere is controlled by the air-sea difference in partial pressure of CO2 and by the efficiency of the transfer processes, the efficiency can be represented by a resistance of the surface and expressed by transfer velocity, k.Measurements made at the Östergarnsholm field station in the Baltic Sea indicate that the CO2 transfer velocity is also a function not only of wind speed, but also of the mixed-layer depth of the water and, to a lesser degree, of the stratification of the atmosphere. The transfer velocity is significantly enhanced by a large mixed-layer depth, the enhancement increasing as the surface cooling increases. The impact of mixed layer depth is expressed by the convective velocity scale of the water (analogous to atmospheric convective scaling).Enhancement due to convection is an important factor affecting the diurnal cycle of air-sea fluxes. Large air-sea temperature differences also occur due to air mass advection. Here water-side convection at wind speeds between 2.5 and 6.5 m s-1 is investigated.The enhancement due to convection can be added to the traditional transfer velocity.
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| 6. |
- Rutgersson, Anna, 1971-, et al.
(författare)
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Observed changes and variability of atmospheric parameters in the Baltic Sea region during the last 200 years
- 2014
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Ingår i: Climate Research (CR). - : Inter-Research Science Center. - 0936-577X .- 1616-1572. ; 61:2, s. 177-190
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Forskningsöversikt (refereegranskat)abstract
- The Baltic Sea is located in Northern Europe and exhibits significant climate variability, with influence of air masses from arctic to subtropical origin. By updating and discussing results described in the framework of the BACC project (BALTEX Assessment of Climate Change for the Baltic Sea Basin), this study presents observed changes in atmospheric parameters during the last 200 yr. Circulation patterns show large decadal variability with a northward shift of storm tracks and increased cyclonic activity in recent decades with increased persistence of weather types. However, the wind climate shows no robust long-term trends, and is dominated by pronounced (multi-)decadal variability. Near-surface temperatures show continued warming, in particular during spring and winter; this is stronger over northern regions. Up to this point, no long-term trends are detectable for precipitation, although some regional indications exist for an increased length of precipitation periods, and possibly an increased risk of extreme precipitation events.
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| 7. |
- Rutgersson, Anna, 1971-, et al.
(författare)
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Oceanic convective mixing and the impact on air-sea gas transfer velocity
- 2011
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 38:2, s. L02602-
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Tidskriftsartikel (refereegranskat)abstract
- Combination of surface water cooling and a deep ocean mixed layer generates convective eddies scaling with the depth of a mixed layer that enhances the efficiency of the airsea transfer of CO2 (and possibly other gases). This enhancement is explained by the convective eddies disturbing the molecular diffusion layer and inducing increased turbulent mixing in the water. The enhancement can be introduced into existing formulations for calculating the air‐ sea exchange of gases by using an additional resistance, due to large‐scale convection acting in parallel with other processes. The additional resistance is expressed here as 1rwc=g (w*qu*w , where w*u*w characterizes the relative role of surface shear andbuoyancy forces
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| 8. |
- Wesslander, Karin, 1976, et al.
(författare)
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Observed carbon dioxide and oxygen dynamics in a Baltic Sea coastal region
- 2011
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963 .- 1879-1573. ; 86:1-2, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- In April 2006, diurnal variations of carbon dioxide (CO2) and oxygen (O2) in the surface water east of Gotland in the Baltic Sea were investigated with a unique multitechnology approach. Several parameters were measured simultaneously providing an overviewof the CO2 system.Moored instrumentswere continuously recording partial pressure of CO2 in the surface water (pCO2 w), currents,mixing,waves, salinity, temperature and O2. Measurements of total alkalinity (AT) and dissolved inorganic carbon (CT) were taken from R/V Skagerak. These measurements were converted to pCO2 w to support the continuous pCO2 w data and also calculate the air–sea exchange of CO2. Additionally, the time derivatives of O2 and CT concentrations in the water were determined using incubations and a Productivity Autosampler (PA). O2 and pCO2 w were significantly anti-correlated and periods dominated of either biological processes, mixing, air–sea exchange or a combination of these were detected. O2 and pCO2 w had a daily cycle and variations occurred on the 1 h time scale. In April 2006, the seawas a CO2 sink and the averaged parameterized air–sea exchange was −1.0±0.6 mmol m−2 h−1.
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