Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
11024631 | Quaternary Science Reviews | 2018 | 14 Pages |
Abstract
Greenland Ice Sheet (GrIS) covers an area of 1.7â¯km2. It has been an important source of climate information and the air temperature history of Greenland is well known. However, the thermal history and temperature conditions of the Greenland bedrock are poorly known. There are only few records on the temperature of the proglacial bedrock and no records on bedrock temperature underneath the ice sheet. The Greenland Analogue Project (GAP) recently investigated hydrological, hydrogeological and geochemical processes in Kangerlussuaq, West Greenland. Because permafrost has a major hydrological impact in Arctic regions, the cryogenic structure of the bedrock was an important research topic. From previous studies it was already known that Kangerlussuaq is located within the zone of continuous permafrost. Temperature profiling in a new research borehole, extending horizontally 30â¯m underneath the ice sheet, revealed that permafrost is 350â¯m deep at the ice margin. This result raised the question how far the permafrost extends under the ice sheet? In order to investigate the thermal properties, we made a series of electromagnetic (EM) soundings at the ice margin area - on proglacial area and on the ice sheet - and detected, that subglacial permafrost extends at least 2â¯km from the ice margin to inland. We also observed a patchy unfrozen sediment layer between the ice and the frozen bedrock. Possible existence of subglacial sediments and their role in ice dynamics has been debated in many recent papers. Our successful campaign shows that geophysics can be used for bedrock investigations through thick ice, which is known to be challenging for electromagnetic methods. Our results provide the first direct evidence supporting the proposed Holocene ice re-advance over frozen ground, and contribute to the discussion on the rapid climate changes in past, to the future of the ice sheet under warming climate and hydrogeology at the ice margin.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geology
Authors
Timo Ruskeeniemi, Jon Engström, Jukka Lehtimäki, Heikki Vanhala, Kimmo Korhonen, Anne Kontula, Lillemor Claesson Liljedahl, Jens-Ove Näslund, Rickard Pettersson,