Multiple-stage deglacial retreat of the southern Greenland Ice Sheet linked with Irminger Current warm water transport

Abstract

There is limited knowledge pertaining to the history of the Greenland Ice Sheet (GIS) during the last glacial-interglacial transition as it retreated from the continental margins to an inland position. Here we use multiproxy data, including ice-rafted debris (IRD); planktonic isotopes; alkenone temperatures; and tephra geochemistry from the northern Labrador Sea, off southwest Greenland, to investigate the deglacial response of the GIS and evaluate its implications for the North Atlantic deglacial development. The results imply that the southern GIS retreated in three successive stages: (1) early deglaciation of the East Greenland margins, by tephra-rich IRD that embrace Heinrich Event 1; (2) progressive retreat during Allerd culminating in major meltwater releases (δ 18 O depletion of 1.2‰) at the Allerd-Younger Dryas transition (12.8-13.0 kyr B.P.); and (3) a final stage of glacial recession during the early Holocene (∼9-11 kyr B.P.). Rather than indicating local temperatures of ambient surface water, the alkenones likely were transported to the core site by the Irminger Current. We attribute the timing of GIS retreat to the incursion of warm intermediate waters along the base of grounded glaciers and below floating ice shelves on the continental margin. The results lend support to the view that GIS meltwater presented a forcing factor for the Younger Dryas cooling. Copyright 2011 by the American Geophysical Union.