NewsNew book! Omstedt A. (2011).
New paper! Wesslander K, Hall P., Hjalmarsson S., Lefevre D., Omstedt A., Rutgersson A., Sahlée E., and A.Tengberg (2011).
New paper! Grimvall, A., and A., Omstedt (2010).
New paper! Omstedt, A., (2010).
Advanced course on process oriented numerical modelling of lakes and coastal seas (OC6310) The main aims of the present course are to provide scientific understanding and well-tested computer codes for aquatic studies of lakes and coastal seas. By starting from simple models the participants will learn how to build up a more advanced understanding and getting confidence in the numerical modelling. Part I of the course introduces the student into numerical modelling and defining a number of relevant aquatic problems. Part II of the course teaches the student how to solve an aquatic problem by modelling and how to document the exercise.
BONUS/Baltic-C day: pH and the effects on our coastal seas. Time: 10.00-14.30, 4:th of November 2010. Place: Hörsalen, Earth Science Center, Gothenburg, Sweden.
Dissertation: Erik Gustafsson The Baltic Sea marine system - human impact and natural variations Opponent: Prof. Fredrik Wulff, Department of Systems Ecology, Stockholm University, Stockholm, Sweden Abstract:
New paper! Omstedt, A., Edman, M., Anderson, L., G., and H., Laudon (2010).
New paper! Wesslander, K., et al. (2010).
New paper! Artur Svansson, (2010). The Swedish oceanographer Vagn Walfrid Ekman (1874-1954, see Figure 1) is best known for his work on shallow ocean circulation, especially his 1905 paper ‘On the influence of the Earth's rotation on ocean currents’. My paper examines Ekman's early work in its contemporary context, outlines his later work (after 1923) on horizontal circulation of ocean currents, and ends with a brief account of his contribution to oceanographic instruments, especially current meters.
New paper! Linders, T. and O. Saetra, (2010). Possible surface warming by strong wind-forcing from polar lows in the North-Atlantic has been investigated using a numerical model for vertical entrainment of waters from a subsurface warm core, and microwave satellite images of sea-surface temperature during polar low events. The hypothesis is based on the frequently observed subsurface warm core in oceans influenced by the North-Atlantic current (NAC) or by outflowing surface water from the Arctic Ocean. CTD-soundings from the Nordic Seas reveal that the waters from the NAC are located under colder and less saline surface waters in winter. For sufficiently strong wind events, turbulent entrainment of this subsurface warm core may lead to a rapid surface warming. Our main findings is that the surface warming of more than 1 °C may take place within a few hours. The result is based on model runs with initial temperature and salinity profiles from CTD-observations. Observational evidence of surface temperatures that support the hypothesis are found in microwave satellite observations from a polar low event. In the case presented here, increased sea-surface temperatures between 1 and 2 °C were observed. We believe that rapid surface warming of this magnitude may be a potential positive feedback mechanism for the cyclone intensity.
New paper! Hansson, D., Eriksson, C., Omstedt, A., and D., Chen (2010). 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.
Inaugation of Prof. Bernd Schneider at University of Gothenburg The Inaugation of Prof. Bernd Schneider at University of Gothenburg is held on 21 May 2010. Details here: http://www.externarelationer.adm.gu.se/External_Relations/Academic_Ceremonies/Inauguration_of_New_Professors_/
6th Study Conference on BALTEX: Changing Water, Energy and Biogeochemical Cycles in the Baltic Sea Basin. Time and place: Miedzyzdroje, Island of Wolin, Poland, 14 - 18 June 2010.
New Guest Professor in Chemical Oceanography Bernd Schneider has been appointed as Guest Professor in Chemical Oceanography, especially biogeochemical processes in coastal seas at University of Gothenburg. The position is at 20% and will increase the cooperation between University of Gothenburg and the Baltic Sea Institute in Warnemuende.
Dissertation: Daniel Hansson Ocean climate variability over recent centuries explored by modelling the Baltic Sea Opponent: Dr. Eduardo Zorita, GKSS Research Institute, Geesthacht, Germany Abstract:
Dissertation: Christin Eriksson Characterizing and reconstructing 500 years of climate in the Baltic Sea Basin Opponent: Prof. Corinna Schrum, Geophysical Institute University of Bergen, Allegaten 70, N-5007 Bergen Norway Abstract:
Dissertation: Christian Nohr Oceanographic studies of the Baltic Sea with emphasis on sea ice and mixing processes Opponent: Prof. Matti Leppäranta, Department of Physical Sciences, Division of Geophysics, University of Helsinki, Finland Abstract:
Dissertation: Torsten Linders Polar low interaction with the ocean Opponents: Prof. Ann-Sofi Smedman, Department of Earth Sciences, Uppsala University and Sen. Lect. Asgeir Sorteberg. Geophysical Institute, University of Bergen Abstract:
Trial lecture: Torsten Linders El Niño: observation, fundamental dynamics and models Time and place: Thursday 14:th of May 2009 at 10.15 AM in Auditorium 1, Goelogibygningen, University of Oslo Summer school!
Anders Omstedt is participating in organizing a summer school on Bornholm island. New paper! Omstedt, A. , Gustafsson, E. and K., Wesslander, (2009). We present and analyse a fully coupled physical–biogeochemical model of the uptake and release of carbondioxide in the Baltic Sea. The modelling includes the interaction between physical (stratification, temperature, salinity, penetration of solarradiation, and ice), chemical (total alkalinity, pH, dissolved inorganic carbon, oxygen, and nutrients), and biological processes (plankton and dissolved organic carbon (DOC)). These processes have been built in to an advanced process-oriented coupled basin ocean model that has been extensively explored and validated for the Baltic Sea. The model captures major physical–chemical and biological response patterns, as evaluated based on observations from the central Baltic Sea, and illustrate the need to include fractional nutrient release in the photic zone for consistency with CO2 observations. The study indicates that long-termv alues of the water partial pressure of carbondioxide were above atmospheric values before industrialization, with a net release of CO2 to the atmosphere. Seasonal variability increased in the modern industrialization era with the inclusion of eutrophication, making the Baltic Sea both a sink and source of CO2 to the atmosphere. Modelling long-term variations in pH indicates the existence of stable conditions before industrialization and slight decrease due to increased atmospheric carbon dioxide concentrations during industrialization. Eutrophication effects may have damped acidification, but have caused increased seasonal pH variability with low values occurring during winter season. New paper! Gustafsson, E.O., and A., Omstedt (2009). In this study, we investigate the Baltic Sea deep water exchange with focus on oxygen conditions. We assumed that the oxygen removal rate associated with decomposition of organic matter is constant, however, we use different rates for different sub-basins. The results obtained from this study of the deep water oxygen dynamics suggest a gradual increase in removal rate from the eastern Gotland Basin to the Danish Straits. Moreover, it is suggested that a drier climate would result in a reduced ventilation of the halocline region due to strong stratification. A wetter climate on the other hand is found to markedly improve the oxygen conditions in the upper deep water as a consequence of a weakened stratification and a more intense wintertime mixing. Havsklimatgruppen deltar i Tritonseminariet Anders Omstedt och Daniel Hansson deltar i Tritonseminariet vid maritim arkeologi och historia på Humanistiska fakulteten vid Göteborgs universitet. Seminariets titel är "Klimatmodellering av våra omgivande hav: En mötesplats för naturvetenskaplig och humanistisk forskning?" och hålls i sal C430 på Humanisten den 3 februari klockan 1500-1700. Välkomna! The University of Gothenburg has recently conferrred the degree of Doctor Honoris Cause on prof. Hans von Storch. Prof. Hans von Storch and Dr Jin-Song von Storch will give a seminar on 24 October at 0930 at the Department of Eath Sciences, Lecture room Nimbus. The seminar will have the following titles: Dr. Jin-Song von Storch, MPI of Meteorology Hamburg:
Prof. Hans von Storch, Inst for Coastal Res, GKSS: Welcome! PhD course in process oriented numerical modelling of lakes, inland seas and oceans The use of computational fluid dynamics to analyse and predict changes in the environment has increased considerable during the past decades. Numerical models are now standard tools in research and a wide range of applications. The main aim of the present course is to stimulate the student to solve aquatic problems using a problem oriented numerical approach. By starting from simple models the participants will learn how to build up a more advanced understanding and getting confidence in the numerical modelling. Part I of the course introduces the student into numerical modelling and defining a number of relevant aquatic problems. Part II of the course teaches the student how to solve an aquatic problem by modelling and how to document the exercise. Students are expected to have competence and skill in use of MS Windows based PC. Also some basic knowledge about FORTRAN or interest in learning FORTRAN during the course. All participants need to register by sending an e-mail to not later than August 26, 2008. More time table and more information about the course can be downloaded here. New paper! Lagner, J., Vihma, T., and A., Omstedt (2008). Review of BALTEX Phase II Objectives. BALTEX. Newsletter 11, pp. 1-3. International BALTEX Secretariet, GKSS, Geestacht, Germany. Download at http://www.baltex-research.eu/ New book! BACC Author Team (2008). Assessment of climate change for the Baltic Sea basin.Series: Regional Climate Studies. ISBN: 978-3-540-72785-9. Springer-Verlag. New paper! Hjalmarsson, S., Wesslander, K., Anderson, L.G., Omstedt, A., Perttilä, M., and L., Mintrop (2008). Distribution, long-term development and mass balance calculation of total alkalinity in the Baltic Sea. Continental Shelf Research 28(4–5), 593–601. DOI 10.1016/j.csr.2007.11.010 During the 20th century, extensively hydrographic investigations had been performed in the Baltic Sea. One of the parameters that have been determined during these historic investigations of the Baltic Sea is the total alkalinity (AT). In this study, this large data set is used together with a specifically developed box model to estimate the in- and outflows of salinity and AT within the different sub-basins. The Baltic Sea receives large amounts of freshwater through river runoff, and AT can be used as a chemical signature of the runoff as its concentration depends on the mineralogy of the drainage basin. Rivers entering the southern part of the Baltic Sea are draining areas rich in limestone, therefore having higher AT than rivers entering the northern part of the Baltic Sea where granite dominates the bedrock. The mean AT in rivers entering a specific region of the Baltic Sea is achieved by the intercept of the regression line when salinity is plotted versus AT for the corresponding data. In this study, the focus is on the Gulf of Finland and the Gulf of Bothnia where the longest time series data are available. There is a common trend with an increase in AT in rivers entering the Gulf of Finland and a decrease in AT in rivers entering the Gulf of Bothnia. New paper! Hansson, D. and A., Omstedt. Modelling the Baltic Sea ocean climate on centennial time scale: temperature and sea ice. Climate Dynamics 30, 763-778. DOI: 10.1007/s00382-007-0321-2. Supporting materials on products page. This study considers the possible use of different kinds of forcing datasets in Baltic Sea ocean climate modelling on centennial time scales, in particular for the past half millennium. We demonstrate that high-quality station data of the past century and gridded multi-proxy reconstructions for the past 500 years can be used with great success but with various levels of detail. We also demonstrate that output data from the state-of-the-art global climate model EcHo-G are not suitable for modelling the Baltic Sea ocean climate. Two climate properties were studied: the annual maximum ice extent (MIB) and the vertically and horizontally integrated annual water temperature. Centennial time scale results indicate that the seventeenth and nineteenth centuries were the coldest centuries, while the 1690s were the coldest decade and 1695 the coldest year in the last 500 years. The results also indicate that the twentieth century was the warmest century with the least MIB of the last 500 years. On a decadal time scale, the 1990s, 1930s and 1730s were the warmest decades and comparable in terms of both water temperature and MIB. The year 1989 had the minimum observed MIB of only 52,000 km2, implying that the Baltic Sea has been partly ice covered in all winters of the past half millennium. Even though different climate forcing mechanisms may operate on the climate system today compared to over the last half millennium, this study cannot clearly state that the region is experiencing climate change outside the natural limits of the past 500 years. New paper! Eriksson, C., Omstedt. A., Overland, JE., Percival, DB., and HO Mofjeld. Characterizing the European Sub-Arctic Winter Climate since 1500 Using Ice, Temperature, and Atmospheric Circulation Time Series. Journal of Climate 20, 5316-5334. DOI: 10.1175/2007JCLI1461.1. This study describes winter climate during the last 500 yr for the greater Baltic Sea region through an examination of well-documented time series of ice cover, sea level pressure, and winter surface air temperatures. These time series have been the focus of previous studies, but here their covariation over different time scales is analyzed based on two modern descriptive statistical techniques, matching pursuit and wavelet analysis. Independently, 15 time periods were found during the last 500 yr with different climatic signatures with respect to winter severity, circulation patterns, and interannual variability. The onsets of these periods are presumably caused largely by perturbations within the system, although correspondences with solar and volcanic activity can be identified for certain of the periods. The Baltic region climate has changes on both centennial and decadal time scales, often with rapid transitions. Major warmer periods were the first half of the eighteenth century and the twentieth century. A common feature for warm (cold) periods is low (high) variability on shorter time scales. Century-scale variability and the modulation of interannual and decadal signals are quite diverse in the temporal records and do not suggest strong periodicities. An “event” type conceptual model therefore appears adequate for characterizing Baltic climate variability. Workshop on Baltic sea ice The Sixth Workshop on Baltic Sea Ice Climate will be held on August 25-28, 2008, at Lammi Biological Station in Finland. More information available from Prof. Matti Leppäranta. New book! Storch, H., Omstedt, A., and H—J., Isemer (2007). BALTEX Assessment of Climate Change for the Baltic Sea basin (BACC), (2007). Chapter 3, pp 41-51. In Information, Communication and Education on Climate Change-European Perspectives.Vol 26. Editors: W., L., Filho, F. Mannke and P., Schmidt-Thome’.Peter Lang International Verlag der Wissenschaften, Frankfurt am Main, Germany. New report! HELCOM, 2007. Climate Change in the Baltic Sea Area – HELCOM Thematic Assessment in 2007. Baltic Sea Environ. Proc. No. 1, pp.49. Prepared by J. F. Pawlek, J.-M. Leppännen based on BALTEX Assessment of Climate Change for the Baltic Sea Basin (BACC). BACC Lead Authors Read the full report here. Article in Kemivärlden Troligen ett varmare hav - Popular article in Kemivärlden What will and what has happened with the climate of the Baltic Sea? The article is available as a pdf (Swedish only). Chronical in Berlingske Tidende, 2007-01-28 Da svenskerne gik over isen til Danmark - Chronical in Berlingske Tidende The winter of 1658 was very severe with thick ice covering the Belt sea and Öresund. The swedish king took advantage of this and launched a surprise attack over the ice on neighbouring Denmark. Read the full story in a chronical by Daniel Hansson published in the Danish newspaper Berlingske Tidende (in Danish only). Also available as a pdf. New paper! Green, M.,J.,A., Liljebladh, B., and A., Omstedt (2006). Physical oceanography and water exchange in the Northern Kvark Strait. Continental Shelf Research, 26, 721-732. The Northern Kvark connects the very fresh Bothnian Bay to the slightly saltier Bothnian Sa in the northern Baltic Sea. Intense field experiments were made in the strait in May 2003 and October-December 2004 to describe the physical oceanography of the strait. Three different hydrographic regimes were identified and a first-order analyses were made on each regime, neglecting friction, rotation, and horizontal gradients. The strait is shown to be barotropically blocked about 45% of the time. The rest of the time there is vertical stratification, which can be described either by two homogenous layers or by linear density and velocity profiles. The flows in the two stratified regimes are shown to be hydraulically controlled. New report! BALTEX (2006): BALTEX Phase II 2003-2012. Science Framework and Implementation Strategy. International BALTEX Secr., Publication, No. 34, pp.92, GKSS, Geestacht, Germany BSSC 2007 The Baltic Sea Science Conference 2007 is to be held at the University of Rostock, March 19-23 2007. Please visit the conference's homepage for more information at http://www.bssc2007.org. 5th Study Conference on BALTEX On 4-8 of June 2007 the 5th study conference on BALTEX will be held on the island of Saaremaa, Estonia. Visit the conference homepage for more information. New paper! Omstedt, A. and D., Hansson, (2006). The Baltic Sea ocean climate system memory andresponse to changes in the water and heat balance components. Continental Shelf Research 26, 236-251. The Baltic Sea climate system is analysed based on observation and mathematical modelling, and steady state and transient-response characteristics are derived and analysed. Some sensitivity experiments are also run based on observed forcing extracted from various Baltic Sea regions representing a range extending from sub-arctic to marine climatic conditions. We show that two important time scales should be considered: one is associated with the water balance (salinity) and the e-folding time is approximately 33 years; the other is associated with the heat balance and the e-folding time is approximately 1 year. Modelling demonstrates that current ocean conditions, starting from known as well as arbitrary initial conditions, can be realistically simulated. Our modelling indicates that salinity is non-linearly dependent on and strongly sensitive to changes in freshwater inflow, in accordance with the findings of other studies. The annual maximum ice extent is strongly sensitive to change in, the winter air temperature over the Baltic Sea. Calculations indicate that the sea will become almost completely ice covered or ice free at Baltic Sea winter air temperatures of 6 and 2 1C, respectively. Changes in the Baltic Sea annual mean water temperature are closely related to the air temperature above the sea surface. However, during climate warming the water and air temperatures may differ due to changes in the surface heat balance components. New paper! Omstedt, A., Chen, Y. and K., Wesslander, (2005). A comparison between the ERA40 and the SMHI gridded meteorological databases as applied to Baltic Sea modelling. Nordic Hydrology, 36(4), 369-380. See also Supporting material under Products. Two gridded meteorological data sets for the Baltic Sea region, both having 1° ´ 1° horizontal resolution, were compared and analysed for use in Baltic Sea modelling. The SMHI 1° ´ 1° data set covers surface parameters with a three-hour time resolution over the 1970–2004 period. The ERA40 data cover analysed and modelled parameters for several atmospheric layers with a six-hour time resolution over the 1957–2002 period. Meteorological variables considered in this analysis were air temperature, wind speed, total cloud cover, relative humidity, and precipitation. In considering Baltic Sea modelling, we examined maximum ice extent, water temperature, salinity, and net precipitation calculations. The two data sets are largely similar and can both be used in Baltic Sea modelling. However, their horizontal resolution is too coarse for resolving marine conditions over the Baltic Sea. This implies, for example, that the ERA40 original surface winds are too low for some Baltic Sea regions. The ERA40 precipitation values are also too low compared with those of the SMHI and other available data. New paper! Rutgersson, A., Omstedt, A. and Y., Chen, 2005. Evaluation of the heat balance components over the Baltic Sea using four gridded meteorological data bases and direct observations. Nordic Hydrology, 36(4), 381-396. See also Supporting material under Products. In this paper, which reports on part of the BALTEX project, various components of the heat balance over the Baltic Sea are calculated using a number of gridded meteorological databases. It is the heat exchange between the Baltic Sea surface and the atmosphere that is of interest. The databases have different origins, comprising synoptic data, data re-analysed with a 3D assimilation system, an ocean model forced with gridded synoptic data, ship data, and satellite data.We compared the databases, and found that the greatest variation between them is in the long- and short-wave radiation values. However, considerable upward long-wave radiation is followed by considerable downward short-wave radiation, so the total radiation component is partly compensated for in the total budget. The variation in the total heat transport in the databases therefore appears smaller (1.5 ± 3 Wm–2) as the average and one standard deviation. The turbulent heat fluxes estimated from satellite data have very low values; this can largely be explained by the method of calculating air temperature, which also produces an unrealistic stratification over the Baltic Sea. The ERA40 data were compared with measured values and there we found a certain land influence even in the centre of the Baltic Proper. The indicated turbulent heat fluxes were too large, mainly in the fall and winter, and the sensible heat flux was too large in a downward direction in spring and summer. New Report! International BALTEX Secretariat Publication No. 31, October 2005: BALTEX PHASE I, 1993-2002, State of the Art Report. Editors: Daniela Jacob and Anders Omstedt.181 pages The present report summaries the main achievements within the BALTEX phase I period. The report includes 15 chapters dealing with the atmosphere, the Baltic Sea, sea ice, land-atmosphere interaction, turbulent fluxes over the Baltic Sea, precipitation, runoff, satellite applications, weather radars, GPS for remote sensing of water vapour, data assimilation, cloud observations and modeling, coupled regional climate modelling. In a synthesis chapter the major achievements are listed.The BALTEX Phase I State of the art Report is now available electronically or as a report via the BALTEX website, see http://www.gkss.de/baltex. New paper! Chen, D. and A. Omstedt (2005). Climate-induced variability of sea level in Stockholm: Influence of air temperature and atmospheric circulation. Advances in Atmospheric Sciences. 22(5),655-664. This study is focused on climate-induced variation of sea level in Stockholm during 1873-1995. After the effect of the land uplift is removed, the residual is characterized and related to large-scale temperature and atmospheric circulation. The residual shows an overall upward trend, although this result depends on the uplift rate used. However, the seasonal distribution of the trend is uneven. There are even two months (June and August) that show a negative trend. The significant trend in August may be linked to fresh water input that is controlled by precipitation. The influence of the atmospheric conditions on the sea level is mainly manifested through zonal winds, vorticity and temperature. While the wind is important in the period January-May, the vorticity plays a main role during June and December. A successful linear multiple-regression model linking the climatic variables (zonal winds, vorticity and mean air temperature during the past two months) and the sea level was established for each month. An independent verification of the model shows that it has a considerable skill in simulating the variability.
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