Manfred A. Lange

Impact of the Eastern Weddell Ice Shelves on water masses in the eastern Weddell Sea

[1]xa0We use a primitive equation Ocean General Circulation Model to simulate the ocean circulation regime in the Eastern Weddell Sea. The computer model ROMBAX (Revisited Ocean Model based on Bryan And Cox) is an improved version of an earlier ocean model, which has been developed to allow the simulation of the flow regime in ice shelf covered regions. The Eastern Weddell Ice Shelf (EWIS) region is of particular importance because of its narrow continental shelf and its location at the inflow of water masses from the east into the southern Weddell Sea. We have compared the simulated flow pattern and water properties in the EWIS region with the available sparse observations. While the general observed structure of temperature and salinity is reproduced, the model tends to overestimate the on-shore flow of warm deep waters. This discrepancy is not large enough to seriously influence the ice shelf – ocean interaction, which is in good agreement with estimates based on field observations. The mean net melt rate is found to be 0.88 m yr−1 (2.1 mSv) and has a strong seasonal cycle. Sensitivity studies with different ice shelf configurations (no melting, no ice shelf, closed cavity) show strong impacts on the water mass properties in the EWIS region, with up to 0.7°C difference in temperature and 0.05 in salinity relative to the control run. Our results suggest that the EWIS region is of substantial importance to water mass preconditioning and formation in the Weddell Sea, although no deep or bottom water formation occurs in the eastern Weddell Sea directly.

Numerical model studies of Antarctic ice-sheet-ice-shelf-ocean systems and ice caps

Abstract The cryosphere is an essential component of the global climate system, equally affecting climate processes significantly and being subject, and particularly sensitive, to changes in climate conditions. Numerical models are an important tool for assessing climate-change impacts on the Antarctic ice–sheet–ice–shelf–ocean system. They not only complement field and satellite remotesensing investigations but are often the only feasible alternative for addressing some of the important parameters and processes. Over the last few years, our group has made significant progress in developing and applying innovative numerical methods. In this paper, we provide a brief overview of some of the methods employed and the major results obtained for a number of case studies in the Atlantic sector of Antarctica.

Global impacts of Arctic climate processes

The polar regions are experiencing major climate and environmental changes due to the combined effects of natural variability and global warming. To address regional Arctic climate processes and their global feedbacks, 53 experts from the United States, Canada, Europe, and Russia gathered for a recent workshop at the Alfred Wegener Institute for Polar and Marine Research, in Potsdam, Germany. n nThe workshop, which was organized by Klaus Dethloff and Annette Rinke, focused on the use of regional models of the Arctic, global coupled climate models, and Arctic impact studies. This article summarizes the main advances and outstanding issues in Arctic modeling that were presented and discussed during the workshop.

Symposium on climate change impacts in the European North

The possible consequences of anthropogenically caused global and climate changes for human society and for the natural environment are an issue of concern to scientists, political decision makers, and the general public. n n n nVarious organizations, particularly the Intergovernmental Panel on Climate Change (IPCC), have pondered this and related issues extensively over the last 10 years. However, there are still large uncertainties about the many facets of these problems. Work toward the IPCCs Third Assessment Report (TAR), that directly supports negotiations concerning the United Nations Framework Convention on Climate Change (UNFCCC), clearly demonstrates that there is an existing need to pay attention, not only to issues at the global, but also at the regional scale. From this, it follows that there is a need to conduct regional climate impact studies for specific parts of the globe, defined by common political, economic, or environmental characteristics.

Antarctica and global change research

The Antarctic, including the continent and Southern Ocean with the subantarctic islands, is a critical area in the global change studies under the International Geosphere-Biosphere Program (IGBP) and the World Climate Research Program (WCRP). Major scientific problems include the impacts of climate warming, the ozone hole, and sea level changes. Large-scale interactions between the atmosphere, ice, ocean, and biota in the Antarctic affect the entire global system through feedbacks, biogeochemical cycles, deep-ocean circulation, atmospheric transport of heat, moisture, and pollutants, and changes in ice mass balances. Antarctica is also a rich repository of paleoenvironmental information in its ice sheet and its ocean and land sediments.