Leibniz Institute for Baltic Sea Research

Warnemunde, Germany

The Leibniz Institute for Baltic Sea Research is a research institution located in Warnemünde , Germany.It is part of the Leibniz-Association, cooperates with the University of Rostock and was founded in 1992. Employing about 160 people the main focus lies on interdisciplinary study of coastal oceans and marginal seas, especially on Baltic Sea related oceanography. The institute is a follow-up of the former Institute of Oceanography which was part of the GDR Academy of Science.The institute is divided in four departments: physical oceanography, marine chemistry, biological oceanography, and marine geology. Central task of the institute is fundamental research but also teaching at the universities of Rostock and Greifswald. IOW has direct access to the research vessel "Maria S. Merian" and can access by request a variety of other medium-sized vessels for longer trips and interdisciplinary tasks from the German research fleet. The institute's facilities are financed by the German Federal Ministry of Education and Research, and the Ministry of Education of Mecklenburg-Western Pomerania. Wikipedia.

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The evasion of elemental mercury (Hg0) from water surfaces is a key process in biogeochemical mercury cycling. Knowledge of the Hg0 diffusion coefficient (DHg0) in water is essential for Hg0 water-air flux calculations, but no measured value has been available. In this study, DHg0was measured in pure water and in water of oceanic salinity within an environmental temperature range between 5°C and 30°C. A diffusion cell was constructed consisting of two chambers separated by an aqueous gel membrane allowing molecular diffusion only. The corresponding parameterizations were developed on the basis of the Eyring equation, which defines an activation energy (Ea) for the diffusion process. The temperature dependences of DHg0(in cm2 s-1) for freshwater, Dfresh Hg0 = 0:0335e-18:63 kJ mol-1/RT, and for seawater, Dsea Hg0 = 0:0335e-0:0011e-11:06 kJ mol-1/RT, with R the gas constant and T the temperature in Kelvin, were thus obtained with an error of ±15%. Whereas the measured Dfresh Hg0 was in good agreement with the theoretical proposals of a molecular dynamics (MD) simulation, Dsea Hg0 was clearly lower, probably because of the unaccounted effect of the polarization of mercury atoms in the salt solution, which hampers diffusion. In geochemistry applications, use of the newly determined Dsea Hg0 instead of the Dfresh Hg0 from MD simulations would have differential effects on determinations of mercury emissions from the world's oceans. The effect on the tropical ocean would be the largest, decreasing the Hg0 water-air flux estimate by 20%. Toward higher latitudes (~50°), the calculated emission would drop by about 10%. On the basis of a recent large data set, the estimated amount of mercury released by the Atlantic Ocean would decrease by approximately 17%. © 2014, by the Association for the Sciences of Limnology and Oceanography, Inc.

Grawe U.,Leibniz Institute for Baltic Sea Research
Ocean Modelling | Year: 2011

Stochastic differential equations (SDEs) offer an attractively simple solution to complex transport-controlled problems, and have a wide range of physical, chemical, and biological applications, which are dominated by stochastic processes, such as diffusion. As for deterministic ordinary differential equations (ODEs), various numerical scheme exist for solving SDEs. In this paper various particle-tracking schemes are presented and tested for accuracy and efficiency (time vs. accuracy). To test the schemes, the particle tracking algorithms are implemented into a community wide used 1D water column model. Modelling individual particles allows a straightforward physical interpretation of the involved processes. Further, this approach is strictly mass conserving and does not suffer from the numerical diffusion that plagues grid-based methods. Moreover, the Lagrangian framework allows to assign properties to the individual particles, that can vary spatially and temporally. The movement of the particles is described by a stochastic differential equation, which is consistent with the advection-diffusion equation. Here, the concentration profile is represented by a set of independent moving particles, which are advected according to the velocity field, while the diffusive displacements of the particles are sampled from a random distribution, which is related to the eddy diffusivity field. The paper will show that especially the 2nd order schemes are accurate and highly efficient. At the same level of accuracy, the 2nd order scheme can be significantly faster than the 1st order counterpart. This gain in efficiency can be spent on a higher resolution for more accurate solutions at a lower cost. © 2010 Elsevier Ltd.

Feistel R.,Leibniz Institute for Baltic Sea Research
Desalination | Year: 2010

To the Gibbs function for seawater endorsed in 2008 by the International Association for the Properties of Water and Steam (IAPWS), an extension to higher temperature and salinity has been developed, based on density measurements at atmospheric pressure, temperatures up to 90 °C and absolute salinities up to 70 g/kg, as recently published by Millero and Huang (2009). In the range considered, the standard uncertainty in density of those data is less than 7 ppm. The new extension improves the applicability of the current standard formulation to hot seawater concentrates as encountered in desiccating seas or desalination plants, and maintains numerical consistency with most of the data used for the original formulation within their experimental uncertainties. Absolute salinity is expressed in the Reference-Composition Salinity Scale of 2008, temperature in the International Temperature Scale of 1990, ITS-90. © 2009 Elsevier B.V. All rights reserved.

Wylezich C.,Leibniz Institute for Baltic Sea Research | Jurgens K.,Leibniz Institute for Baltic Sea Research
Environmental Microbiology | Year: 2011

The oxic-anoxic transition zone of the Black Sea comprises a large suboxic zone as well as anoxic and sulfidic waters. While the prokaryotes and biogeochemical cycles that characterize this zone have been frequently studied, little is known about the diversity or ecology of its microbial eukaryotes. Here, we present the first broad qualitative report of the protist species composition in the Black Sea redoxcline using molecular tools. Fingerprint analysis from the whole redoxcline revealed a complex community structure of metabolically active protists with distinct shifts along the redox gradient. Additionally, 18S rRNA gene clone libraries were used to compare protist species composition of suboxic and sulfidic water layers. Among the ciliates, sequences related to Pleuronema and Strombidium were dominant in both water layers whereas sequences affiliated with anaerobic plagiopylids and Cyclidium were detected only in the sulfidic zone. Among the flagellates, mainly stramenopiles (mostly bicosoecids and chrysophytes) occurred throughout the redoxcline. In the sulfidic zone we found stramenopile sequences but also euglenozoans, jakobids and choanoflagellates that were related to clonal sequences from other anoxic marine habitats, thus indicating the existence of globally distributed groups of anoxic flagellates. Higher species diversity in the sulfidic zone and about twice as many novel sequence types of ciliates and stramenopiles compared with the suboxic layer emphasizes the importance of anoxic, sulfidic waters as habitat for high protist diversity although the function of these organisms is yet unknown. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

Burchard H.,Leibniz Institute for Baltic Sea Research | Hetland R.D.,Texas A&M University
Journal of Physical Oceanography | Year: 2010

This numerical modeling study quantifies for the first time the contribution of various processes to estuarine circulation in periodically stratified tidal flow under the impact of a constant horizontal buoyancy gradient. The one-dimensional water column equations with periodic forcing are first cast into nondimensional form, resulting in a multidimensional parameter space spanned by the modified inverse Strouhal number and the modified horizontal Richardson number, as well as relative wind speed and wind direction and the residual runoff. The along-tide momentum equation is then solved for the tidal-mean velocity profile in such a way that it is equated to the sum of the contributions of tidal straining (resulting from the temporal correlation between eddy viscosity and vertical shear), gravitational circulation (resulting from the depth-varying forcing by a constant horizontal buoyancy gradient), wind straining, and depth-mean residual flow (resulting from net freshwater runoff). This definition of tidal straining does not only account for tidal asymmetries resulting from horizontal buoyancy gradients but also from wind straining and residual runoff. For constant eddy viscosity, the well-known estuarine circulation analytical solution with polynomial residual profiles is directly obtained. For vertically parabolic and constant-in-time eddy viscosity, a new analytic solution with logarithmic residual profiles is found, showing that the intensity of the gravitational circulation scales with the horizontal Richardson number. For scenarios with realistic spatially and temporally varying eddy viscosity, a numerical water column model equipped with a state-of-the-art two-equation turbulence closure model is applied to quantify the individual contributions of the various processes to estuarine circulation. The fundamental outcome of this study is that, for irrotational flow with periodic stratification and without wind forcing and residual runoff, the tidal straining is responsible for about two-thirds and gravitational circulation is responsible for about one-third of the estuarine circulation, proportionally dependent on the horizontal Richardson number, and weakly dependent on the Strouhal number. This new and robust result confirms earlier estimates byH. Burchard and H. Baumert, who suggested that tidal straining is the major generation mechanism for estuarine turbidity maxima. However, a sensitivity analysis of the model results to details of the turbulence closure model shows some uncertainty with respect to the parameterization of sheared convection during flood. Increasing down-estuary wind straining and residual runoff reduce the quantitative contribution of tidal straining. For relatively small horizontal Richardson numbers, the tidal straining contribution to estuarine circulation may even be reversed by down-estuary wind straining. © 2010 American Meteorological Society.

Neumann T.,Leibniz Institute for Baltic Sea Research
Journal of Marine Systems | Year: 2010

The expected climate change is of growing interest on the regional scale, including the Baltic Sea. However, simulations with global models do not sufficiently resolve the regional impact. Consequently, dynamic downscaling methods are being used to convert the results obtained in global models to the regional scale. In the present study, two regional data sets for greenhouse gas emission scenarios, A1B and B1, for the period 1960 to 2100, were used to force transient simulations with a 3D ecosystem model of the Baltic Sea. The results showed that the expected warming of the Baltic Sea is 1-4 K, with a decrease in salinity and a much reduced sea-ice cover in winter. In addition, the season favoring cyanobacterial blooms is prolonged, with the spring bloom in the Northern Baltic Sea beginning earlier in the season, while the oxygen conditions in deep water are expected to improve slightly. © 2009 Elsevier B.V. All rights reserved.

Burchard H.,Leibniz Institute for Baltic Sea Research | Schuttelaars H.M.,Technical University of Delft
Journal of Physical Oceanography | Year: 2012

Tidal straining, which can mathematically be described as the covariance between eddy viscosity and vertical shear of the along-channel velocity component, has been acknowledged as one of the major drivers for estuarine circulation in channelized tidally energetic estuaries. In this paper, the authors investigate the role of lateral circulation for generating this covariance. Five numerical experiments are carried out, starting with a reference scenario including the full physics and four scenarios in which specific key physical processes are neglected. These processes are longitudinal internal pressure gradient forcing, lateral internal pressure gradient forcing, lateral advection, and the neglect of temporal variation of eddy viscosity. The results for the viscosity-shear covariance are correlated across different experiments to quantify the change due to neglect of these key processes. It is found that the lateral advection of vertical shear of the along-channel velocity component and its interaction with the tidally asymmetric eddy viscosity (which is also modified by the lateral circulation) is the major driving force for estuarine circulation in well-mixed tidal estuaries. © 2012 American Meteorological Society.

Grawe U.,Leibniz Institute for Baltic Sea Research | Burchard H.,Leibniz Institute for Baltic Sea Research
Climate Dynamics | Year: 2012

Globally-coupled climate models are generally capable of reproducing the observed trends in the globally averaged atmospheric temperature or mean sea level. However, the global models do not perform as well on regional/local scales. Here, we present results from four 100-year ocean model experiments for the Western Baltic Sea. In order to simulate storm surges in this region, we have used the General Estuarine Transport Model (GETM) as a high-resolution local model (spatial resolution ≈ 1 km), nested into a regional atmospheric and regional oceanic model in a fully baroclinic downscaling approach. The downscaling is based on the global model ECHAM5/MPI-OM. The projections are imbedded into two greenhouse-gas emission scenarios, A1B and B1, for the period 2000-2100, each with two realisations. Two control runs from 1960 to 2000 are used for validation. We use this modelling system to statistically reproduce the present distribution of surge extremes. The usage of the high-resolution local model leads to an improvement in surge heights of at least 10% compared to the driving model. To quantify uncertainties associated with climate projections, we investigate the impact of enhanced wind velocities and changes in mean sea levels. The analysis revealed a linear dependence of surge height and mean sea level, although the slope parameter is spatially varying. Furthermore, the modelling system is used to project possible changes within the next century. The results show that the sea level rise has greater potential to increase surge levels than does increased wind speed. The simulations further indicate that the changes in storm surge height in the scenarios can be consistently explained by the increase in mean sea level and variation in wind speed. © 2011 Springer-Verlag.

Van Der Lee E.M.,Leibniz Institute for Baltic Sea Research | Umlauf L.,Leibniz Institute for Baltic Sea Research
Journal of Geophysical Research: Oceans | Year: 2011

The dynamics of near-inertial motions, and their relation to mixing, is investigated here with an extensive data set, including turbulence and high-resolution velocity observations from two cruises conducted in 2008 (summer) and 2010 (winter) in the Bornholm Basin of the Baltic Sea. In the absence of tides, it is found that the basin-scale energetics are governed by inertial oscillations and low-mode near-inertial wave motions that are generated near the lateral slopes of the basin. These motions are shown to be associated with persistent narrow shear-bands, strongly correlated with bands of enhanced dissipation rates that are the major source of mixing inside the permanent halocline of the basin. In spite of different stratification, near-inertial wave structure, and atmospheric forcing during summer and winter conditions, respectively, the observed dissipation rates were found to scale with local shear and stratification in a nearly identical way. This scaling was different from the Gregg-Henyey-type models used for the open ocean, but largely consistent with the MacKinnon-Gregg scaling developed for the continental shelf. Copyright 2011 by the American Geophysical Union.

Voss M.,Leibniz Institute for Baltic Sea Research
Philosophical transactions of the Royal Society of London. Series B, Biological sciences | Year: 2013

The ocean's nitrogen cycle is driven by complex microbial transformations, including nitrogen fixation, assimilation, nitrification, anammox and denitrification. Dinitrogen is the most abundant form of nitrogen in sea water but only accessible by nitrogen-fixing microbes. Denitrification and nitrification are both regulated by oxygen concentrations and potentially produce nitrous oxide (N2O), a climate-relevant atmospheric trace gas. The world's oceans, including the coastal areas and upwelling areas, contribute about 30 per cent to the atmospheric N2O budget and are, therefore, a major source of this gas to the atmosphere. Human activities now add more nitrogen to the environment than is naturally fixed. More than half of the nitrogen reaches the coastal ocean via river input and atmospheric deposition, of which the latter affects even remote oceanic regions. A nitrogen budget for the coastal and open ocean, where inputs and outputs match rather well, is presented. Furthermore, predicted climate change will impact the expansion of the oceans' oxygen minimum zones, the productivity of surface waters and presumably other microbial processes, with unpredictable consequences for the cycling of nitrogen. Nitrogen cycling is closely intertwined with that of carbon, phosphorous and other biologically important elements via biological stoichiometric requirements. This linkage implies that human alterations of nitrogen cycling are likely to have major consequences for other biogeochemical processes and ecosystem functions and services.

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