Collaborative Research: Development of paleo-proxy to test the sensitivity of the Southern Greenland Ice Sheet to future warming

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Carlson 0902571University of Wisconsin ? MadisonA significant missing component in paleo-reconstructions of GIS behavior has been the lack of an unambiguous ice sheet tracer. The development of such a tracer for the Greenland Ice Sheet (GIS) retreat and aerial extent is proposed using terrigenous provenance markers and the different bedrock terrane ages of southern Greenland (Archean versus varying Proterozoic ages). Specifically, streams will be sampled for suspended load sediment from the geologic terranes of southern Greenland. Suspended load sediment will be measured for trace-element and Sr-Nd-Pb isotope composition, and magnetic properties of the sediment will be determined. These data will be compared with previously made and new measurements on a core off of southern Greenland from a well-studied sediment sequence spanning the last 430 kyrs and 5 interglacials. Isotope studies on piston core samples will focus on the silt size fraction in order to minimize the influence of far traveled clay size sediment. Ice rafted sediment will also be avoided. Trace element records combined with previous and newly obtained magnetic records will provide estimates of the response time of the southern GIS to a warming climate by identifying the timing and duration of ice sheet retreat. The Sr-Nd-Pb isotope tracers will allow calculations of sediment sources and when ice retreated off portions of southern Greenland, thus estimating its contribution to higher sea levels. In particular, the disappearance of relatively young Proterozoic sediment at the core site places the southern GIS margin behind its current location. A subsequent reduction in Archean sediment and dominance of intermediate age Proterozoic sediment places the southern GIS margin in central Greenland.