Controls on Surging in East Greenland Derived From a new Glacier Inventory

Glacier surging is often classified as a distinct type of bimodal flow behaviour. Yet, studies of surging show a spectrum in surge behaviour, where initiation and termination, as well velocity development and periodicity can vary greatly from glacier to glacier. It is clearly possible that different classes of surge behaviour involve different controls on glacier flow. Environmental and glacial characteristics that distinguish surge-type from normal glaciers can serve as benchmark data to test surge theories and to identify boundary conditions for surging. Different regional glacier population analyses have revealed that surge potential is controlled by a combination of glacier geometry, local climate, thermal and substrate conditions. In this study we use the results of multivariate logit modelling of a surge cluster in central East Greenland and compare the controls on surging in this region to those found for other regions. Central East Greenland is characterised by a variety of glacier types, such as small icecaps and valley glaciers, and large dissection glaciers draining local ice plateaux. Many of these are tidewater terminating and former surges have caused extreme calving events. For 258 local glaciers, of which 71 are of surge type, a suite of glacial and environmental factors were analysed. These data were collected from remotely sensed data (SAR ERS 1/2 and Landsat 7 images), aerial photographs and maps and were assembled in a GIS. This provides a baseline digital glacier inventory for East Greenland. Variables of interest are geologic controls (eg. physical properties), geometric controls (eg. glacier type, shape and complexity) and mass balance related properties. This study uses a range of variables previously tested for Svalbard surge controls (Jiskoot et al., 2000), and in addition focuses on variables representing glacier complexity, such as channel curvature, tributary arrangements and shape factors. Results show that geologic boundary conditions for surging vary greatly between cluster regions, whereas geometric controls show remarkable similarities. This study provides new insights into controls on ice dynamics and flow instabilities.