Late Weichselian and Holocene behavior of the Greenland Ice Sheet in the Kejser Franz Josef Fjord system, NE Greenland

Abstract

To better understand the past retreat patterns and chronologies of major marine-terminating outlet glaciers, the Late Weichselian and Holocene glacial history of a NE Greenland fjord system is reconstructed using new and previously published swath bathymetry and high-resolution seismic data, supplemented with multi-proxy analysis of sediment cores. The investigated area extends more than 190 km, including Fosters Bugt, Kejser Franz Josef Fjord, Nordfjord and Moskusoksefjord, the drainage routes for Waltershausen Gletscher, one of the largest outlet glaciers in the NE sector of the Greenland Ice Sheet. A complex of moraine ridges identified in Fosters Bugt show former stillstand positions during this period, and, alongside radiocarbon ages, supports the theory of a maximum ice front position in the outer coastal areas during the Younger Dryas-Preboreal period. The retreat moraines distributed within the Kejser Franz Josef Fjord system provide evidence of a stepwise retreat during the last deglaciation, whereby rapid retreat was interrupted by episodes of stillstands and/or readvances of the grounding line. The fjord system was mostly deglaciated prior to 7.8 ka cal BP, with an estimated average retreat rate ranging between 33 and 96 m a⁻¹ since the Younger Dryas. Following this, only minor ice advances in the inner fjords have been identified. The sediment supply from Waltershausen Gletscher dominated the Kejser Franz Josef Fjord, Nordfjord and outer Moskusoksefjord throughout the Holocene period, whereas in the middle and inner Moskusoksefjord the sediment deposits reflect a more local catchment area. The estimated average retreat rate is in the same order of magnitude as the rates from fjords of northern Fennoscandia, indicating the same overall control for the deglaciation, ice melting from increased Northern Hemisphere summer insolation that peaked in Early Holocene.