Johannes Oerlemans – författare

Proceedings of the Symposium on Glacier Fluctuations and Climatic Change, held in Amsterdam, June 1-5, 1987

Climate modelling is a field in rapid development, and the fltudy of cryospheric processes has become an important part of it. On smaller time scales, the effect of snow cover and sea ice on the atmospheric circulation is of concern for long-range weather forecasting. Thinking in decades or centuries, the effect of a C02 climatic warming on the present-day ice sheets, and the resulting changes in global sea level, has drawn a lot of attention. In particular, the dynamics of marine ice sheets (ice sheets on a bed that would be below sea level after removal of ice and full isostatic rebound) is a subject of continuous research. This interest stems from the fact that the West Antarctic Ice Sheet is a marine ice sheet which, according to some workers, may be close to a complete collapse. The Pleistocene ice ages, or glacial cycles, are best characterized by total ice volume on earth, indicating that on 4 5 large time scales (10 to 10 yr) ice sheets are a dominant component of the climate system. The enormous amount of paleoclimatic information obtained from deep-sea sediments in the last few decades has led to a complete revival of iriterest in the physical aspects of the Pleistocene climatic evolution.

Few scientists doubt the prediction that the antropogenic release of carbon dioxide in the atmosphere will lead to some warming of the earth's climate. So there is good reason to investigate the possible effects of such a warming, in dependence of geographical and social­ economic setting. Many bodies, governmental or not, have organized meetings and issued reports in which the carbon dioxide problem is defined, reviewed, and possible threats assessed. The rate at which such reports are produced still increases. However, while more and more people are getting involved in the 'carbon dioxide business', the number of investigators working on the basic problems grows, in our view, too slowly. Many fundamental questions are still not answered in a satisfactory way, and the carbon dioxide building rests on a few thin pillars. One such fundamental question concerns the change in sea level associated with a climatic warming of a few degrees. A number of processes can be listed that could all lead to changes of the order of tens of centimeters (e. g. thermal expansion, change in mass balance of glaciers and ice sheets). But the picture of the carbon dioxide problem has frequently be made more dramatic by suggesting that the West Antarctic Ice Sheet is unstable, implying a certain probability of a 5 m higher sea-level stand within a few centuries.

Proceedings of the Symposium on Glacier Fluctuations and Climatic Change, held in Amsterdam, June 1-5, 1987

This book gives a comprehensive overview of our present understanding of the Earth's cryosphere, its changes and their consequences for mean sea level changes. Since the middle of the 19th century there has been an increase of sea level height by 20-25 cm. Some 8-10 cm of this is due to net losses from glaciers, the remainder being due to mass losses from land ice and thermal expansion of the oceans. The mean sea level rise is slowly accelerating; at present it is some 3 mm/year. Recent space observations made by the GRACE satellite combined with ocean temperature and volume measurements have enabled the separate contributions to sea level rise from melting ice and from thermal expansion to be better estimated. The estimation of mean sea level change is complicated by changes in land level due to tectonic effects and to ongoing changes following the latest major glaciation. The book gives an up-to-date survey of our present knowledge of this crucial subject.

Climate modelling is a field in rapid development, and the fltudy of cryospheric processes has become an important part of it. On smaller time scales, the effect of snow cover and sea ice on the atmospheric circulation is of concern for long-range weather forecasting. Thinking in decades or centuries, the effect of a C02 climatic warming on the present-day ice sheets, and the resulting changes in global sea level, has drawn a lot of attention. In particular, the dynamics of marine ice sheets (ice sheets on a bed that would be below sea level after removal of ice and full isostatic rebound) is a subject of continuous research. This interest stems from the fact that the West Antarctic Ice Sheet is a marine ice sheet which, according to some workers, may be close to a complete collapse. The Pleistocene ice ages, or glacial cycles, are best characterized by total ice volume on earth, indicating that on 4 5 large time scales (10 to 10 yr) ice sheets are a dominant component of the climate system. The enormous amount of paleoclimatic information obtained from deep-sea sediments in the last few decades has led to a complete revival of iriterest in the physical aspects of the Pleistocene climatic evolution.

Few scientists doubt the prediction that the antropogenic release of carbon dioxide in the atmosphere will lead to some warming of the earth's climate. So there is good reason to investigate the possible effects of such a warming, in dependence of geographical and social­ economic setting. Many bodies, governmental or not, have organized meetings and issued reports in which the carbon dioxide problem is defined, reviewed, and possible threats assessed. The rate at which such reports are produced still increases. However, while more and more people are getting involved in the 'carbon dioxide business', the number of investigators working on the basic problems grows, in our view, too slowly. Many fundamental questions are still not answered in a satisfactory way, and the carbon dioxide building rests on a few thin pillars. One such fundamental question concerns the change in sea level associated with a climatic warming of a few degrees. A number of processes can be listed that could all lead to changes of the order of tens of centimeters (e. g. thermal expansion, change in mass balance of glaciers and ice sheets). But the picture of the carbon dioxide problem has frequently be made more dramatic by suggesting that the West Antarctic Ice Sheet is unstable, implying a certain probability of a 5 m higher sea-level stand within a few centuries.