The Relationship between East Greenland Current Temperature and Southern Greenland Ice Sheet Runoff during the Last Two Deglaciations

Recent observations of outlet glaciers of the Greenland Ice Sheet (GIS) suggest that they are sensitive to subsurface water warming, but these observations are limited to only the past decade. Here we investigate past changes in East Greenland Current temperature and their relationship to southern GIS melting. We use Neogloboquadrina pachyderma (sinistral) Mg/Ca as a proxy for pycnocline temperatures, and sediment Ti concentration (a GIS runoff proxy) from Eirik Drift core MD99-2227 for the last and penultimate deglaciations (TI and TII). During TI, Mg/Ca temperatures show a gradual warming trend of ~6 degrees C from 15 ka to a peak at 9 ka that corresponds with increasing GIS runoff. However, an earlier increase in runoff at ~19 ka does not appear to be related to pycnocline warming, as Mg/Ca temperatures remain constant at approximately 1 degrees C. Pycnocline warming also occurred concurrent with increased GIS runoff during TII, though the magnitude of warming during this interval was only ~3 degrees C. Peak pycnocline interglacial temperatures were reached after the peak in GIS runoff. Nevertheless, our data show a correspondence between East Greenland Current warming and increased southern GIS melting, demonstrating that this recently observed relationship may have also operated over significantly longer periods in the past.