1.
Omstedt, Anders, 1949
(författare)
The Development of Climate Science of the Baltic Sea Region
2017
Ingår i: Oxford Research Encyclopedia of Climate Science. - : Oxford University Press.
Bokkapitel (övrigt vetenskapligt/konstnärligt) abstract
Dramatic climate changes have occurred in the Baltic Sea region caused by changes in orbital movement in the earth–sun system and the melting of the Fennoscandian Ice Sheet. Added to these longer-term changes, changes have occurred at all timescales, caused mainly by variations in large-scale atmospheric pressure systems due to competition between the meandering midlatitude low-pressure systems and highpressure systems. Here we follow the development of climate science of the Baltic Sea from when observations began in the 18th century to the early 21st century. The question of why the water level is sinking around the Baltic Sea coasts could not be answered until the ideas of postglacial uplift and the thermal history of the earth were better understood in the 19th century and periodic behavior in climate related time series attracted scientific interest. Herring and sardine fishing successes and failures have led to investigations of fishery and climate change and to the realization that fisheries themselves have strongly negative effects on the marine environment, calling for international assessment efforts. Scientists later introduced the concept of regime shifts when interpreting their data, attributing these to various causes. The increasing amount of anoxic deep water in the Baltic Sea and eutrophication have prompted debate about what is natural and what is anthropogenic, and the scientific outcome of these debates now forms the basis of international management efforts to reduce nutrient leakage from land. The observed increase in atmospheric CO and its effects on global warming have focused the climate debate on trends and generated a series of international and regional assessments and research programs that have greatly improved our understanding of climate and environmental changes, bolstering the efforts of earth system science, in which both climate and environmental factors are analyzed together.
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3.
Omstedt, Anders, 1949, et al.
(författare)
Future changes in the Baltic Sea acid-base (pH) and oxygen balances
2012
Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 64
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.
4.
Omstedt, Anders, 1949, et al.
(författare)
Progress in physical oceanography of the Baltic Sea during the 2003–2014 period
2014
Ingår i: Progress in Oceanography. - : Elsevier BV. - 0079-6611 .- 1873-4472. ; 128, s. 139-171
Tidskriftsartikel (refereegranskat) abstract
We review progress in Baltic Sea physical oceanography (including sea ice and atmosphere–land interactions) and Baltic Sea modelling, focusing on research related to BALTEX Phase II and other relevant work during the 2003–2014 period. The major advances achieved in this period are: Meteorological databases are now available to the research community, partly as station data, with a growing number of freely available gridded datasets on decadal and centennial time scales. The free availability of meteorological datasets supports the development of more accurate forcing functions for Baltic Sea models. In the last decade, oceanographic data have become much more accessible and new important measurement platforms, such as FerryBoxes and satellites, have provided better temporally and spatially resolved observations. Our understanding of how large-scale atmospheric circulation affects the Baltic Sea climate, particularly in winter, has improved. Internal variability is strong illustrating the dominant stochastic behaviour of the atmosphere. The heat and water cycles of the Baltic Sea are better understood. The importance of surface waves in air–sea interaction is better understood, and Stokes drift and Langmuir circulation have been identified as likely playing an important role in surface water mixing in sea water. We better understand sea ice dynamics and thermodynamics in the coastal zone where sea ice interaction between land and sea is crucial. The Baltic Sea’s various straits and sills are of increasing interest in seeking to understand water exchange and mixing. There has been increased research into the Baltic Sea coastal zone, particularly into upwelling, in the past decade. Modelling of the Baltic Sea–North Sea system, including the development of coupled land–sea–atmosphere models, has improved. Despite marked progress in Baltic Sea research over the last decade, several gaps remain in our knowledge and understanding. The current understanding of salinity changes is limited, and future projections of salinity evolution are uncertain. In addition, modelling of the hydrological cycle in atmospheric climate models is severely biased. More detailed investigations of regional precipitation and evaporation patterns (including runoff), atmospheric variability, highly saline water inflows, exchange between sub-basins, circulation, and especially turbulent mixing are still needed. Furthermore, more highly resolved oceanographic models are necessary. In addition, models that incorporate more advanced carbon cycle and ecosystem descriptions and improved description of water–sediment interactions are needed. Thereoceanographic coupled model systems. These and other research challenges are addressed by the recently formed Baltic Earth research programme, the successor of the BALTEX programme, which ended in 2013. Baltic Earth will treat anthropogenic changes and impacts together with their natural drivers. Baltic Earth will serve as a network for earth system sciences in the region, following in the BALTEX tradition but in a wider context.
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7.
Hansson, Daniel, 1980, et al.
(författare)
Reconstruction of river runoff to the Baltic Sea, AD1500-1995
2011
Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418. ; 31, s. 696-703
Tidskriftsartikel (refereegranskat) abstract
In this paper we reconstructed river runoff to the Baltic Sea since 1500 using temperature and atmospheric circulation indices, showing the important atmospheric processes for river runoff in different regions. Runoff appears to be strongly linked to temperature, wind and rotational circulation components in the northern region and Gulf of Finland, but more associated with rotational and deformation circulation components in the south. No significant long-term change has been detected in total river runoff to the Baltic Sea for 500 years, although decadal and regional variability is large. Analysis of runoff sensitivity to temperature shows that the south region may become drier with rising air temperatures. This is in contrast to the north region and Gulf of Finland where warmer temperatures are associated with more river runoff. Over the past 500 years the total river runoff to the Baltic Sea has decreased by 3% (450 m3/s) per degree Celsius increase.
8.
Omstedt, Anders, 1949
(författare)
Guide to process based modelling of lakes and coastal seas
2011
Bok (övrigt vetenskapligt/konstnärligt) abstract
The intent of Guide to process based modeling of lakes and coastal seas is to introduce its readers to the subject, giving them a basic scientific understanding of and needed tools for aquatic studies. The book encourages the reader to solve geophysical problems using a systematic, process based approach. This approach divides the studied water body into dynamically relevant parts or natural sub-basins and identifies the major processes involved in the problem. Based on field observations and simplifications, the dynamics are then expressed mathematically, and tested carefully against relevant analytical solutions, extremes, and observations. After a background in lake and coastal seas physics and biogeochemistry the modeling started by addressing the Ekman ocean boundary layer. This gave the reader insight into numerical modeling and the importance of considering analytical solutions; we also learned how to test a solution for grid independence and time resolution. The next section considered the modeling of lakes. A simple slab model was developed for shallow lakes, while for deep lakes we considered how to model the effects of pressure on the temperature of maximum density. We learned how to read meteorological data and calculate corresponding heat fluxes at the atmosphere–water interface. The first ocean model was then developed by adding the salinity equation to the lake model. Basin geometry and river runoff were added to the model and the heat and salt conservation properties were investigated. The reader discovered that salt conservation was quite easily achieved; heat conservation, however, required that sea ice be included in the model. This was the topic of the next section, which considered the modeling of sea ice with its new boundary conditions. The importance of turbulent modeling was studied in the next section. Various models, from zero-equation to two-equation models, were investigated. The reader learned the importance of employing good turbulent models and of considering deepwater mixing. Then, we addressed how to include tides in the modeling by adding the horizontal pressure gradients modeled from tidal sea level variations. The first biogeochemical application was to model oxygen dynamics, and the reader learned how to add one more equation to the physical equation system. Another equation for plankton growth and mineralization was added in the next section. Oxygen concentration was related to plankton growth and mineralization, and the reader learned that understanding the nutrient dynamics called for further equations. One nutrient equation, representing phosphorus, was then added to the marine system and nutrient limitation was investigated. To learn more about the carbon system, we modeled the inorganic carbon dynamics. The importance of introducing biological processes when modeling the CO2 system was further investigated. The construction of nets of coupled sub-basins was then analyzed, and the first section addressed the modeling of two coupled basins. This exercise taught the reader to add one more sub-basin to the system. The PROBE-Baltic marine system was introduced, and the first application included only physical processes. Using this version, we could study several model aspects, such as turbulent mixing, dense bottom currents, heat and ice dynamics, water and heat budgets, and air–sea–land interactions. The second application included oxygen concentrations as well, giving a tool for studying, for example, the interaction between inflow dynamics and oxygen reduction due to biological mineralization. Finally, the third application included physical–biogeochemical dynamics, in particular, the CO2 system. This version allowed the study of aspects such as acid–base (pH) balance, biological production, and interaction with climate. Various aspects of lakes and coastal seas were illustrated with a number of exercises, and their solutions were worked through in Chapter 6. The appendixes to the book touch on various matters, including a short introduction to FORTRAN, nomenclature, data and programs needed for the book, the PROBE Manual, and a discussion on reconstructions of past aquatic conditions. With growing access to data on the Internet, it will become increasingly easier to analyze various water bodies, ranging from small lakes to coastal seas and ocean basins. Much can be learned using a process based approach, and one of its strengths is that it focuses on process understanding rather than numerical methods. It is therefore my hope that this book will stimulate students and researchers to develop their modeling skill and make model codes and data transparent to other research groups.
9.
Shaltout, Mohamed, et al.
(författare)
Modelling the water and heat balances of the Mediterranean Sea using a two-basin model and available meteorological, hydrological, and ocean data
2015
Ingår i: Oceanologia. - : Elsevier BV. - 0078-3234. ; 57:2, s. 116-131
Tidskriftsartikel (refereegranskat) abstract
This paper presents a two-basin model of the water and heat balances of the Western and Eastern Mediterranean sub-basins (WMB and EMB, respectively) over the 1958—2010 period using available meteorological and hydrological data. The results indicate that the simulated temperature and salinity in both studied Mediterranean sub-basins closely follow the reanalysed data. In addition, simulated surface water in the EMB had a higher mean temperature (by approximately 1.68C) and was more saline (by approximately 0.87 g kg -1) than in the WMB over the studied period. The net evaporation over the EMB (1.52 mm day >sup>-1) was approximately 1.7 times greater than over the WMB (0.88 mm day -1). The water balance of the Mediterranean Sea was controlled by net inflow through the Gibraltar Strait and Sicily Channel, the net evaporation rate and freshwater input. The heat balance simulations indicated that the heat loss from the water body was nearly balanced by the solar radiation to the water body, resulting in a net export (import) of approximately 13 (11) W m-2 of heat from the WMB (to the EMB).
10.
Omstedt, Anders, 1949, et al.
(författare)
Modelling the contributions to marine acidification from deposited SOx, NOx, and NHx in the Baltic Sea: Past and present situations
2015
Ingår i: Continental Shelf Research. - : Elsevier BV. - 0278-4343 .- 1873-6955. ; 111:B, s. 234-249
Tidskriftsartikel (refereegranskat) abstract
© 2015. We have examined the effects of historical atmospheric depositions of sulphate, nitrate, and ammonium from land and shipping on the acid-base balance in the Baltic Sea. The modelling considers the 1750-2014 period, when land and ship emissions changed greatly, with increasing carbon dioxide concentrations, SOx, NOx, and NHx emissions, and nutrient loads.The present results indicate that Baltic Sea acidification due to the atmospheric deposition of acids peaked around 1980, with a pH cumulative decrease of approximately 10-2 in surface waters. This is one order of magnitude less than the cumulative acidification due to increased atmospheric CO2. The acidification contribution of shipping is one order of magnitude less than that of land emissions. However, the pH trend due to atmospheric acids has started to reverse due to reduced land emissions, though the effect of shipping is ongoing.The effect of strong atmospheric acids on Baltic Sea water depends on the region and period studied. The largest total alkalinity sink per surface area is in the south-western Baltic Sea where shipping is intense. Considering the entire Baltic Sea over the 2001-2010 period, the pH changes are approximately -3×10-3 to -11×10-3 and -4×10-4 to -16×10-4 pH units attributable to all emissions and ship emissions only, respectively. The corresponding changes in total alkalinity are approximately -10 to -30μmolkg-1 and -1 to -4μmolkg-1 attributable to all emissions and ship emissions only, respectively.
