Antarctica’s Role in Global Climate over Different Time Scales

Summary

Polar ice sheets and glaciers contain well-ordered archives of ancient ice that fell as snow years to millions of years ago. The atmospheric dust particles, soluble chemicals, and gases trapped in the ice provide a unique history of past changes in atmospheric composition and climate. Vostok station was settled onto the East Antarctic plateau by the Soviet Antarctic Expeditions on December 16th, 1957, during IPY, at a location corresponding to the geomagnetic pole. Since then the station was operating almost continuously, and drilling operations were conducted by skilful wintering teams. Following the Antarctic Treaty, which promoted the scientific Endeavour, and thanks to the SCAR committee which gathered scientists, an international collaboration (bipartite and later tri-partite) on the Vostok ice core studies has been established. At this site of East Antarctica the ice thickness amounts to 3750 m and the snow accumulation rate is only 2.1 cm of water equivalent per year. Such conditions offer a rare opportunity to obtain a long climatic record with relatively high time-resolution. By the mid 1980’s, a first climate record covering an entire climatic cycle (150,000 years) along with a record of CO2 preserved in the air bubbles was obtained and published. By the end of 1998, as the deep drilling reached older ice, the climate record was extended back to 400,000 years depicting 4 climatic cycles. More recently two new Antarctic ice cores provided a longer record: EPICA DC (800,000 years) and Dome Fuji (700,000 years).Under the influence of anthropogenic activities, recent climate change creates a real concern about the future of civilization on our planet. Climate scientists are trying to provide realistic assessments of how our climate will change in the future. In this respect the glacial archives from Polar Regions are of importance. International collaboration helped to decipher the mysteries of the ice ages, and the Vostok CO2-climate correlation was and is still greatly impacting the ongoing research on carbon cycle in relation with climate changes. In this sense, the Vostok record has been one of the “icones” used through the various IPCC assessments dealing with the fate of the anthropogenic CO2.Reconstructions of past environments are now recognized as an important element in climatic and environmental studies because they (a) allow assessment of the degree of natural variability and place current observed changes in a broader perspective (b) help us to understand causes and mechanisms of change and (c) contribute to validating models by comparison of output with empirical data. The last few hundred thousand years form the context in which we can learn how the Earth System works.In January 1998, the collaborative project between Russia, France and the United States of drilling the hole 5G at Vostok yielded the longest ice core ever recovered, reaching a depth of 3623 m. The drilling stopped 130 m above Lake Vostok, a deep subglacial water body which extends below the ice sheet over an area similar to Lake Ontario today. The recovery of ice refrozen from lake water (accretion ice) opens an unexpected window on this unknown environment. The discovery of more than 200 subglacial lakes in Antarctica generates a great deal of scientific and public discussion and speculation about origin, nature and fate of the subglacial lakes as well as their possible contribution to the ice sheet dynamics. The scientific aspects of the exploration are currently discussed within the SCAR committee SALE.

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