CAUSES OF RAPID EAST ANTARCTIC GLACIER TONGUE RESPONSES

Rapid local and regional climate changes of the recent past are often reflected in the behavior of polar ice sheets, and in particular their coastal margins and accompanying marine ice sheets. Both gradual and catastrophic ice margin changes may be sensitive indicators of on-going and future climatic change. Such ice margin changes have been variously documented in Antarctica since the early 1900s, and may be best domonstrated by the Mertz and Ninnis Glacier Tongues of George V Coast (130°00'E - 160°00'E) in the Pacific Ocean sector. The earliest reliable account of these glacier tongues is from the Australasian Antarctic Expedition of 1911-1914. Subsequent accounts reveal dramatic advance and decline of these features in the past century suggesting regional climatic influences accompanied by local conditions such as ice sheet mass at or near the melting temperature, relatively high subglacial slopes facilitating basal sliding, and short term dynamic influences or ice volume increases accellerating ice stream flow. The unusual sizes and abrupt advance and decline of these glacier tongues suggest anomalous conditions of origin, dynamical evolution or glacial history when compared with other Antarctic glacier tongues. This conclusion is supported by analysis of subglacial gemorphology, ice volumes and ice flow rates.