ABSTRACT: A 1000-year perspective on Arctic warming provided by 14C dating of quartz and vegetation emerging beneath the ice caps of northern Baffin Island, Arctic Canada.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Ice caps on the interior plateau of northern Baffin Island, Arctic Canada, provide a millennial scale perspective on 20th century warming. The numerous plateau ice caps are small (< 50 km2), cold-based, and in recent years, everywhere below equilibrium line altitude. The remaining ice caps have lost more than half their area since 1958 AD; a continuation of current climatic regime, even with no additional warming, will lead to the disappearance of all ice on the plateau by 2070 AD. Several techniques have been used in concert to place the current melt into a larger picture of ice-cap history since Laurentide deglaciation ~6 ka. Lichen trimlines represent the Little Ice Age maximum extent of multi-season ice, of which only 3% remains today. Because the ice caps are thin and cold, they have not eroded their beds, and vegetation killed by the first snows during their inception is now being exposed each year as the ice margin recedes. 50 AMS radiocarbon dates on dead vegetation emerging beneath the melting ice margin suggest sudden expansions of ice caps, and continuous ice cover until present at about 1450 AD, 1280 AD and 900 AD. Cosmogenic 14C concentrations in rocks just appearing from beneath the receding ice cap margins show that during the past 2800 years, the land has been free of ice for only 800 years, further demonstrating the unusual nature of the current warming. Two peaks in ice-cap inception, 1280 AD and 1450 AD, coincide with episodes of explosive volcanism that resulted in the heaviest aerosol loading of the past millennium, and with intervals of reduced solar luminosity, suggesting that these mechanisms may have initiated ice-cap inception, and that strong positive feedbacks maintained the ice caps.

Bibliography of Canadian Geomorphology