Marine Test of the Sensitivity of Ice Streams Entering Baffin Bay to Ocean Warming from LGM through Deglaciation, with an Emphasis on Central West Greenland Ice Streams

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The proposed research will evaluate how ocean warming contributed to past ice sheet dynamics through study of the Last Glacial Maximum (LGM) through early Holocene behavior of ice streams draining into Baffin Bay. This research will provide a new context for understanding ice sheet response to past warm periods, in particular, the Bølling/Allerod interstadial period, which hosted rapid sea level rise and abrupt climate warming after the LGM. At the LGM the Greenland Ice Sheet (GIS) was one of three large ice sheets terminating via large, fast flowing ice streams into Baffin Bay. This project willstudy the past history, dynamics, and ice-sheet ocean interactions in Baffin Bay, and the role of ocean warming in ice sheet demise, via multi-proxy analysis of existing (2008 and 2009) sediment cores from the West Greenland continental slope. Data from this proposal will be used to model freshwater flux from the ice streams, and will provide new information on what role the Greenland Ice Sheet played in past sea-level rise as the LGM ice sheet began to shed as much as 4.6 m of sea level equivalent. The research will test three hypotheses using foraminiferal faunas, sediment mineralogy, stable isotope analyses, stratigraphy of iceberg rafted detritus (IRD), and visible diffuse spectral reflectance data:1. The western margin of the GIS advanced during stadials and retreated during interstadials inresponse to the presence or absence of ocean warming via the West Greenland Current.2. Peaks of ice-berg rafted material (IRD) result from two distinct processes: Proximal IRD isderived from retreat of the GIS off the shelf edge, whereas distal IRD results from collapse of theLaurentide Ice Sheet and Innutian Ice Sheet/NW Greenland margins in northern Baffin Bay.3. Advection of warm water along the West Greenland margin causes enhanced melting ofnorthern Baffin Bay icebergs and sea ice at the polar front, forming an IRD belt along the W.Greenland margin, which preserves a record of ice sheet-discharge events under conditions ofocean warming. The GIS is losing mass in response to modern warming. It stores enough fresh water to raise global sea level by 6.5 m, making its sensitivity to warming a major societal concern. It is anticipated that the sensitivity and response of the GIS to past warming, which are the foci of this project, will help constrain projections of the future evolution of the GIS.