Submarine landform assemblage for Svalbard surge-type tidewater glaciers

Abstract

Svalbard has about 800 km of ice cliffs where tidewater glaciers reach the sea (Blaszczyk et al. 2009). A number of these glaciers are of surge type (Dowdeswell et al. 1991; Hagen et al. 1993) and have undergone rapid advances of a few years in duration followed by slow retreat over decades, in response to variations in their basal hydrological system driven largely by geometric and thermal changes (e.g. Murray et al. 1998, 2000). These fluctuations, which take place over beds composed mainly of soft sediments, have been monitored using satellite imagery, aerial photographs and early maps (e.g. Ottesen et al. 2008; Flink et al. 2015). The seafloor geomorphology of surging tidewater glaciers in Svalbard, revealed after glacier-terminus retreat, contains a well-defined landform assemblage (e.g. Solheim & Pfirman 1985; Ottesen & Dowdeswell 2006; Ottesen et al. 2008; Flink et al. 2015). Seafloor sediments in two Spitsbergen fjords, inner Van Keulenfjorden and Borebukta (Fig. 1), exemplify the landforms typically deposited by recent tidewater-glacier surges in Svalbard. Van Keulenfjorden is 40 km long and 5 km wide, and is subdivided into two basins. Several glaciers with a total area of about 900 km2 drain into inner Van Keulenfjorden (Fig. 1a). Here, Van Keulenfjorden is about 2.5 km wide with a maximum depth of 80 m before shallowing to a prominent ridge about 10 km from the 2002 tidewater-glacier termini (Fig. 1a). Borebukta is a 10 km long inlet on the north side of Isfjorden (Fig. 1b), about 1 km wide and 50 m deep at the present tidewater-glacier front, deepening to about 70 m offshore (Fig. 1b). Further out it shallows once more to a 10 m deep threshold at the fjord entrance. The 22 km long Borebreen and 14 …