Submarine landforms and the behavior of a surging ice cap since the last glacial maximum: The open-marine setting of eastern Austfonna, Svalbard

Abstract

Multi-beam swath bathymetry data and Topographic Parametric Sonar (TOPAS) 3.5 kHz sub-bottom acoustic profiles were acquired from the inlet of Hartogbutka, an open-marine setting offshore of Austfonna, northeastern Nordaustlandet, Svalbard, the largest ice cap in the Eurasian Arctic. Using these marine geophysical data, the seafloor morphological and sedimentary evidence of former ice extent and dynamics of the three drainage basins (Basins 3, 4, and 5) adjacent to Hartogbukta were examined. Submarine landforms and landform assemblages that provide evidence of past ice dynamics are described and interpreted in the context of previous studies of surge-affected submarine environments elsewhere in Svalbard. A sequence of four distinct ice-flow episodes in Hartogbukta, from the late Weichselian deglaciation to the present, is identified to explain the morphological evolution of the seafloor. A full-glacial ice sheet extended over Hartogbukta during the late Weichselian, flowing ESE. At intervals throughout the Holocene, the drainage basins adjacent to Hartogbukta probably underwent repeated surges. Most recently, Basins 3 and 4 probably surged as one cohesive ice mass in the late 1800s and Basin 5 most likely underwent a less extensive surge in the 20th century. These ice-flow events are interpreted in the context of the glaciology and known glacial history of Austfonna and the NW Barents Sea. The 200 km-long ice cliffs of eastern Austfonna provide an unusual and important analog for open-marine deposition that would have been much more prevalent under full-glacial conditions where ice sheets in many parts of the Arctic advanced from fjord systems onto the adjacent continental shelves.