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W
e have all seen or heard of the evidence of ice melting across the Arctic. The clear retreat of glaciers and loss of sea ice provide stark and iconic examples of climate change that are impossible to ignore. The implications are profound for Earth’s climate, ecosystems, socioeconomics, security, northern communities, as well as the unique beauty of Arctic landscapes. There remains a vast amount of land ice across the Arctic – the Greenland Ice Sheet, the ice caps of the Canadian Archipelago, and the icefields and glaciers in Alaska and the Yukon. In the cold upper reaches of these glaciers, snowfall accumulates a record of chemical changes in the atmosphere and physical changes in our climate system. The snow is eventually compressed into glacier ice with layers that are analogous to rings in a tree. The deeper you go, the older the ice
is, sometimes older than 100,000 years at the bottom of the Greenland Ice Sheet. Accessing the climate history contained in Arctic ice is a considerable challenge – the best locations are remote and cold, and the oldest ice is hundreds to thousands of meters deep. To confront this challenge, international scientific cooperation has been essential. For example, North American and European scientists have collaborated for over half a century on ice core projects on the Greenland Ice Sheet. Ice drilling, where cylinders of ice are recovered in 1–3 meter sections beginning at the surface and continuing to the bedrock, has improved dramatically in terms of speed and quality of ice recovered. The careful and detailed study of these ice cores has revealed a number of fundamental insights into the Arctic system that are critical to our climate action decisions. A widely recognized aspect of the Arctic ice core record is the clear evidence for abrupt climate changes. These large re-organizations
of the climate system occurred many times during the last glacial period (roughly 60,000 to 10,000 years ago). What makes them particularly important is the rapid nature of the transitions – large changes in temperature, precipitation, and dustiness in less than ten years – and that they had global impacts. The North Atlantic region and Antarctica were tightly connected within decades via atmospheric and ocean circulation during each of these abrupt climate changes. The ice core record clearly illustrates that over the course of recent Earth history, there is a direct and important connection between the Arctic and global climate. This Arctic-global connection is also apparent in the ice core record in terms of recent human impacts on the Arctic atmosphere. The emissions history of a range of pollutants with health and environmental impacts – lead, mercury, sulfate, nitrate, persistent organic pollutants from industrial activity, mining and smelting, and fossil fuel use – can be precisely reconstructed
Stories from the Ice A H I S T O R Y O F A R C T I C C L I M AT E A N D
E N V I R O N M E N TA L C H A N G E T O L D I N I C E C O R E S By KARL KREUTZ, Professor, University of Maine and CAMERON WAKE,Research Professor, University of New Hampshire and ERICH OSTERBERG, Associate Professor, Dartmouth College and ALISON CRISCITIELLO, Director, Canadian Ice Core Lab, University of Alberta
