Changes of hydrothermal structure of Austre Grønfjordbreen and Fridtjovbreen Glaciers in Svalbard

Abstract

The results of ground-based RES studies (20 MHz) at the Austre Gronfjordbreen and Fridtjovbreen glaciers on Nordenskiold Land, Svalbard, spring 2010–2012, were compared with previous airborne RES data (620 MHz) of 1979 to understand the hydrothermal structure and its changes with time for these twinned glaciers. Temperature measurements in 9 shallow ice bore holes (down to 20 m) of spring 2013, and other RES and bore-hole data (1977–2005) were also considered. Both glaciers now are polythermal ones. The ratio of cold/temperate ice volumes in Austre Gronfjordbreen is 83 and 17 per cent, and in Fridtjovbreen is 26 and 74 per cent. The water content in temperate ice estimated from radio wave velocity is ca. 2–5%. Total water content in temperate ice of Austre Gronfjordbreen is estimated as 1,8–4,5∙10 −3 km 3 , and in Fridtjovbreen as 74–85∙10 −3 km 3 . Over the past 33 years (1979–2012) the average thickness of the cold ice in Austre Gronfjordbreen decreased by about 34 m, and thickness of temperate ice by 9 m. In Fridtjovbreen the cold ice has thinned by 87 m, but the temperate ice became thicker by 48 m. These differences in hydrothermal structure changes of the neighboring glaciers with common climatic history are attributed to the additional effect of Fridtjovbreen surge in 1991–1997 resulted in its additional internal heating.