Constraints on the Greenland Ice Sheet since the Last Glacial Maximum from sea-level observations and glacial-rebound models

Abstract

Geomorphological descriptions of changes in the extent of the Greenland Ice Sheet (GIS) have been combined with glacial-isostatic-adjustment models to reproduce the sea-level history of Greenland since the Last Glacial Maximum (LGM). The contribution to past sea-level change around Greenland due to ice-load changes outside of that region has been considerable (± 10's of meters), while still contributing a rise of several mm yr −1 today. The isostatic contribution to relative sea level around Greenland from changes in the GIS is found by iteratively perturbing preliminary ice models with different LGM extents and deglaciation starting times. The resulting first-order model that provides the best agreement between observed and predicted sea level contributes 3.1 and 1.9 m water-equivalent of additional ice relative to present-day ice volumes at the LGM and Younger Dryas, respectively. The GIS in most areas does not appear to have extended far onto the continental shelf, the exceptions being southern-most Southwest Greenland and northern East Greenland, as well as at the coalescence of the Northwest Greenland and Innuitian Ice Sheets. Changes in ice thickness since the LGM were >500 m along the present-day outer coast and >1500 m along some parts of the present-day ice margin. The observed mid- to late-Holocene fall in sea level to below the present-day level and the subsequent transgression seen in some areas implies that the GIS retreated behind the present-day margin by distances of the order of 40 km before readvancing.