Modelling of the Svalbard fjord Hornsund

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Exposure status of sea-dumped chemical warfare agents in the Baltic Sea

About 50 000 tons of chemical weapons (CW) were dumped to the Baltic Sea after the Second World War. Munitions are located in the deep areas of the Baltic Sea, and there they act as a point source of contamination to the ecosystem. Corroded munitions release chemical warfare agents (CWAs) to nearby water and sediments. In this study we investigated known dumpsites (Bornholm, Gotland and Gdansk Deep) and dispersed chemical munitions, to evaluate the extent of contamination of nearby sediments, as well as to assess the degradation process of released CWA. It was found that CWA-related phenylarsenic chemicals (Clark I, Clark II and Adamsite) and sulfur mustard are released to the sediments and undergo environmental degradation to chemicals, of which some remain toxic. The extent of pollution of released CWAs and their corresponding degradation products reaches more than 250 m from the CW objects, and seem to follow a power curve decrease of concentration from the source. Bornholm Deep is characterised with the highest concentration of CWAs in sediments, but occasional concentration peaks are also observed in the Gdansk Deep and close to dispersed munitions. Detailed investigation of spreading pattern show that the range of pollution depends on bottom currents and topography.Peer reviewe

Supporting marine environment research by modeling

The Centre of Informatics – Tri-City Academic Supercomputer and Network (CI TASK) was founded over twenty-five years ago, in 1994. It was a very important initiative undertaken as a result of rapid development of computer technology and one of its main goals was to integrate the computer resources of scientific communities in the Tri-City. CI TASKstarted to provide computing resources and the first steps in the world of high-performance computing must have been proved to be a significant challenge. The scientific community of the Institute of Oceanology has been cooperating with that computing centre since the very beginning.Currently, CI TASKprovides the widest set of tools and hardware that can be used for ocean modeling purposes. The main goal of this work is expression of appreciation and gratitude for the people who have contributed to the developing of this institution and helped in the work using their tools.CI TASK has been helpful in a great number of past and present tasks, however, in this paper we would like to present only three results of our work – a coupled ice-ocean model of the Baltic Sea, assessment of contamination for potential leak age from chemical munition dumped after the Second World War, and the currently operating SatBaltic system

Ridging, strength, and stability in high‐resolution sea ice models

The article of record as published may be found at http://dx.doi.org/10.1029/2005JC003355In multicategory sea ice models the compressive strength of the ice pack is often assumed to be a function of the potential energy of pressure ridges. This assumption, combined with other standard features of ridging schemes, allows the ice strength to change dramatically on short timescales. In high-resolution (~10 km) sea ice models with a typical time step (~1 hour), abrupt strength changes can lead to large internal stress gradients that destabilize the flow. The unstable flow is characterized by large oscillations in ice concentration, thickness, strength, velocity, and strain rates. Straightforward, physically motivated changes in the ridging scheme can reduce the likelihood of abrupt strength changes and improve stability. In simple test problems with flow toward and around topography, stability is significantly enhanced by eliminating the threshold fraction G* in the ridging participation function. Use of an exponential participation function increases the maximum stable time step at 10-km resolution from less than 30 min to about 2 hours. Modifying the redistribution function to build thinner ridges modestly improves stability and also gives better agreement between modeled and observed thickness distributions. Allowing the ice strength to increase linearly with the mean ice thickness improves stability but probably underestimates the maximum stresses.Climate Change Prediction Program (CCPP) and the Scientific Discovery through Advanced Computing (SciDAC) program of the U.S. Department of Energy’s Office of ScienceShelf-Basin Interaction (SBI) program of the U.S. National Science FoundationCCPP and through the International Arctic Research Center’s Arctic Ocean Model Intercomparison Project (AOMIP)Arctic Region Supercomputing Center (ARSC) through the U.S. Department of Defense High Performance Computer Modernization Program (HPCMP

Variability in the distribution of phytoplankton as affected by changes to the main physical parameters in the Baltic Sea

An integrated ecological system model was used to determine the influence on Baltic phytoplankton of the long-term variability in the sea's main physical parameters. A three-dimensional coupled sea-ice model was developed. A simple ecosystem was added to the sea-ice model and used to estimate phytoplankton variability during long-term changes in the main atmospheric forces. Scenarios similar to those of climate were performed by altering the main physical parameters such as temperature, wind speed, solar and thermal radiation (in different configurations). The influence of the variability in these parameters on phytoplankton is discussed

Particulate organic carbon in the southern Baltic Sea: numerical simulations and experimental data

Particulate Organic Carbon (POC) is an important component in the carbon cycle of land-locked seas. In this paper, we assessthe POC concentration in the Gdańsk Deep, southern Baltic Sea. Our study is based on both a 1D POC Model and current POCconcentration measurements. The aim is twofold: (i) validation of simulated concentrations with actual measurements, and (ii) a qualitativeassessment of the sources contributing to the POC pool.        The POC model consists of six coupled equations: five diffusion-typeequations for phytoplankton, zooplankton, pelagic detritus and nutrients (phosphate and total inorganic nitrogen) and one ordinarydifferential equation for detritus at the bottom. The POC concentration is determined as the sum of phytoplankton, zooplankton and pelagicdetritus concentrations, all expressed in carbon equivalents. Bacteria are not simulated in this paper.        The observed large fluctuations of POC concentrations are attributedto its appreciable seasonal variability. The maximum concentration of POC varied between 870 mgC m-3 inMay and 580 mgC m-3 in September, coinciding with the period of maximum dead organic matter andphytoplankton biomass concentrations. The results of the numerical simulations are in good agreement with observed values. The differencebetween the modelled and observed POC concentrations is equal to 3-28% and depends on the month for which the calculations were made,although no time trend of the difference is observed. The conclusion is that the numerical simulations are a sufficiently good reflectionof POC dynamics in the Baltic

Numerical modelling of POC dynamics in the southern Baltic under possible future conditions determined by nutrients, light and temperature

This paper discusses predictions of particulate organic carbon (POC) concentrations in the southern Baltic Sea. The study is based on the one-dimensional Particulate Organic Carbon Model (1D POC), described in detail by Dzierzbicka-Głowacka et al. (2010a). The POC concentration is determined as the sum of phytoplankton, zooplankton and dead organic matter (detritus) concentrations. Temporal changes in the phytoplankton biomass are caused by primary production, mortality, grazing by zooplankton and sinking. The zooplankton biomass is affected by ingestion, excretion, faecal production, mortality and carnivorous grazing. The changes in the pelagic detritus concentration are determined by the input of dead phytoplankton and zooplankton, the natural mortality of predators, faecal pellets, and sinks - sedimentation, zooplankton grazing and biochemical decomposition. The model simulations were done for selected locations in the southern Baltic Sea (Gdańsk Deep, Bornholm Deep and Gotland Deep) under predicted conditions characterized by changes of temperature, nutrient concentrations and light availability. The results cover the daily, monthly, seasonal and annual POC concentration patterns in the upper water layer. If the assumed trends in light, nutrients and temperature in the southern Baltic correctly predict the conditions in 2050, our calculations indicate that we can expect a two- to three-fold increase in POC concentration in late spring and a shift towards postponed maximum POC concentration. It can also be anticipated that, as a result of the increase in POC, oxygenation of the water layer beneath the halocline will decrease, while the supply of food to organisms at higher trophic levels will increase