Formation and disintegration of a high‐arctic ice‐cored moraine complex, Scott Turnerbreen, Svalbard

Abstract

Englacial debris structures, morphology and sediment distribution at the frontal part and at the proglacial area of the Scott Turnerbreen glacier have been studied through fieldwork and aerial photograph interpretation. The main emphasis has been on processes controlling the morphological development of the proglacial area. Three types of supraglacial ridges have been related to different types of englacial debris bands. We suggest that the sediments were transported in thrusts, along flow lines and in englacial meltwater channels prior to, and during a surge in, the 1930s, before the glacier turned cold. Melting‐out of englacial debris and debris that flows down the glacier front has formed an isolating debris cover on the glacier surface, preventing further melting. As the glacier wasted, the stagnant, debris‐covered front became separated from the glacier and formed ice‐cored moraine ridges. Three moraine ridges were formed outside the present ice‐front. The further glacier wastage formed a low‐relief proglacial area with debris‐flow deposits resting directly on glacier ice. Melting of this buried ice initiated a second phase of slides and debris flows with a flow direction independent of the present glacier surface. The rapid disintegration of the proglacial morphology is mainly caused by slides and stream erosion that uncover buried ice and often cause sediments to be transported into the main river and out of the proglacial area. Inactive stream channels are probably one of the morphological elements that have the best potential for preservation in a wasting ice‐cored moraine complex and may indicate former ice‐front positions.