Post Glacial Rebound Models and Relative Sea-level Observations from East Greenland

It is important, when using altimetry data to reconstruct ice sheet mass balance, to accurately remove the effects of vertical movements in the solid Earth caused by Post Glacial Rebound (PGR). Holocene relative sea- level (RSL) data constrain PGR in Greenland, but their quality and distribution is patchy. For example, one widely cited model in mass balance analyses uses RSL data from two closely located sites, Skeldal and Mesters Vig, to constrain Holocene PGR predictions for c. 2000 km of the east coast of Greenland (ICE5G, Tarasov and Peltier (2002)). Here we address this issue by presenting the first ever RSL data set for southeast Greenland. Our work is based on an analysis of four isolation basins and two lakes above the local marine limit from a field area located close to Kulusuk. Our data define a rapid fall in RSL from at least 70 m asl at c. 11 ka cal. yrs BP to close to present level by c. 6.7 ka cal. yrs BP. There is no evidence that RSL was higher than present for the last 6000 years. We note significant differences between our new data and several GPR model predictions. Although some models suggest RSL only recently fell to present level in east Greenland, none predict the late-Holocene RSL rise and crustal subsidence that our new observations suggest.