Gerold Wefer – författare

The South Atlantic plays a significant role as a link between the Antarctic Ocean and the North Atlantic, both in terms of the heat budget of the North Atlantic and the circulation of the entire ocean. The heat and mass exchanges between the Antarctic Ocean and the South Atlantic during the Late Quaternary have been investigated over the past ten years, including their impact on world climate. This has required the study of present-day early diagenetic processes in the water column and sediments, as well as sediment properties that have a close relationship to environmental parameters ("proxies"), which can be used to decipher past conditions (temperature, salinity, productivity, etc. ). The interdisciplinary research project "The South Atlantic in the Late Quaternary - Reconstruction of material budgets and current systems" was a long-term scientific program at Bremen University. This program benefited from the sample material gained on several expeditions with the research vessels Meteor and Polarstern. This book presents the summarized results of the various topics of study in 30 articles arranged in seven sections.

Europe is a continent with a high coast-to-surface ratio, and European seas encompass a broad range of settings and regimes. The sustainable development of living and non-living marine resources, the protection of the marine environment and the provision of marine-based services are critical to economic prosperity and to the quality of life of European citizens. Addressing these concerns, marine-science researchers conducted a workshop reviewing major topics of European marine research. This publication contains overview and thematic background papers, as well as reports and recommendations for future research covering topics such as ocean-climate coupling, biogeochemistry, coastal and shelf processes, and ecosystem functioning/biodiversity.

Ocean margins are the transitional zones between the oceans and continents. They represent dynamic systems in which numerous processes shape the environment and result in impacting the utilization and hazard potentials for humans. These processes are influenced by a variety of steering mechanisms, from mountain building and climate on the land to tectonics and sea-level fluctuations in ocean margins. This book examines various aspects of regulation for the long-term development of ocean margins, of the impact of fluids and of the dynamics of benthic life at and below the seafloor in ocean margin systems.

The book is on methods of reconstruction of past climate, climate changes, oceanography of the South Atlantic (including the Southern Ocean) and the cycling of biochemical components in the ocean. Information about past ocean conditions is provided by so-called paleoceanographic proxies (parameters with approximate unobservable environmental variables, e.g. surface water temperature). Use of proxies and their development has been a major theme of the Collaborative Research Project at the University of Bremen for almost 10 years. In this volume we summarize our results in relation to these proxy studies. Each chapter gives an overview of a specific proxy, provides particular findings obtained in the South Atlantic and ends with an outlook on future perspectives with respect to the proxy described. Therefore it is suitable for lecturers, graduate students and scientists working in the field of climate reconstruction from ocean sediments.

The global environment is changing rapidly under the impact of human activities. An important element in this change is related to global climate modification. Experts from the natural and social sciences with a strong interest in history discussed common topics of great interest to society. Can the study of climate and history help in devising strategies for coping with this change? What might be the type of information most useful in this context? What are the pitfalls awaiting the unwary? These and similar questions were discussed during a four-day workshop. The resulting proceedings contain comprehensive papers of broad interest, thematic back-ground papers and reports of study groups. Apart from scientists, the papers should interest graduate students and lecturers.

Ocean margins are the transitional zones between the oceans and continents. They represent dynamic systems in which numerous processes shape the environment and result in impacting the utilization and hazard potentials for humans. These processes are influenced by a variety of steering mechanisms, from mountain building and climate on the land to tectonics and sea-level fluctuations in ocean margins. This book examines various aspects of regulation for the long-term development of ocean margins, of the impact of fluids and of the dynamics of benthic life at and below the seafloor in ocean margin systems.

The South Atlantic plays a critical role in the couplingofoceanic processes between the Antarctic and the lower latitudes. The Antarctic Ocean, along with the adjacent southern seas, is of substantial importance for global climate and for the distributionofwater masses because itprovides large regions ofthe world ocean with intermediate and bottom waters. In contrast to the North Atlantic, the Southern Ocean acts more as an "information distributor", as opposed to an amplifier. Just as the North Atlantic is influencedby the South Atlantic through the contributionofwarm surface water,the incomingsupply ofNADW - in the area of the Southern Ocean as Circumantarctic Deep Water - influences the oceanography ofthe Antarctic. The competing influences from the northern and southern oceans on the current and mass budget systems can be best studied in the South Atlantic. Not only do changes in the current systems in the eastern Atlantic high-production regions affect the energy budget, they also influence the nutrient inventories, and therefore impact the entire productivity ofthe ocean. In addition, the broad region of the polar front is a critical area with respect to productivity-related circulation since it is the source of Antarctic Intermediate Water. Although theAntarctic Intermediate Watertoday liesdeeper than the water that rises in the upwelling regions, it is the long-term source ofnutrients that are ultimately responsible for the supply oforganic matter to the sea floor and to sediments.

Europe is a continent with a high coast-to-surface ratio, and European seas encompass a broad range of settings and regimes. The sustainable development of living and non-living marine resources, the protection of the marine environment and the provision of marine-based services are critical to economic prosperity and to the quality of life of European citizens. Addressing these concerns, marine-science researchers conducted a workshop reviewing major topics of European marine research. This publication contains overview and thematic background papers, as well as reports and recommendations for future research covering topics such as ocean-climate coupling, biogeochemistry, coastal and shelf processes, and ecosystem functioning/biodiversity.

Paleoceanographic proxies provide infonnation for reconstructions of the past, including climate changes, global and regional oceanography, and the cycles of biochemical components in the ocean. These prox­ ies are measurable descriptors for desired but unobservable environmental variables such as tempera­ ture, salinity, primary productivity, nutrient content, or surface-water carbon dioxide concentrations. The proxies are employed in a manner analogous to oceanographic methods. The water masses are first characterized according to their specific physical and chemical properties, and then related to particular assemblages of certain organisms or to particular element or isotope distributions. We have a long-standing series of proven proxies available. Marine microfossil assemblages, for instance, are employed to reconstruct surface-water temperatures. The calcareous shells of planktonic and benthic microorgan­ isms contain a wealth of paleoceanographic information in their isotopic and elemental compositions. Stable oxygen isotope measurements are used to detennine ice volume, and MglCa ratios are related to water temperatures, to cite a few examples. Organic material may also provide valuable infonnation, e. g. , about past productivity conditions. Studying the stable carbon isotope composition of bulk organic matter or individual marine organic components may provide a measure of past surface-water CO 2 conditions within the bounds of certain assumptions. Within the scope of paleoceanographic investigations, the existing proxies are continuously evolving and improving, while new proxies are being studied and developed. The methodology is improved by analysis of samples from the water column and surface sediments, and through laboratory experiments.

In the summer of 1994 (Aug. 15 - 18) about 220 oceanographers and paleoceanographers from Western Europe, the USA, Africa, South America, Russia and Lithuania met at Bremen University to present and discuss the results of recent research on present and past circulation in the South Atlantic. The symposium was organised by Gerold Siedler (University of Kiei) and Gerold Wefer (University of Bremen), assisted by a "Scientific Programme Committee", which included W.H. Berger, K. Herterich, N.G. Hogg, Y. Ikeda, J.H.F. Jansen, J.R.E. Luetjeharms, J. Merle, R.G. Peterson, and DJ. Webb. The local organisation was in the hands of Barbara Donner. A symposium on the South Atlantic seemed timely and appropriate because the results from a number of recent projects in oceanography and marine geosciences needed to be integrated into existing knowl- edge. Thus, monitoring programs have been in operation since 1991 as part of the World Ocean Circu- lation Experiment (WOCE). These programs included studies of the meridional water-mass and heat transports, the western boundary currents, and deep- and bottom-water transports in the Brazil Basin.Also comprehensive studies are being carried out in the context ofIGBP Core Projects PAGES (Past Global Changes) and JGOFS (Joint Global Ocean Flux Study), generating new data for the various current and production systems of the South Atlantic.