Satellite archives reveal abrupt changes in behavior of Helheim Glacier, southeast Greenland

• Published in: Journal of glaciology Vol. 62; no. 231; pp. 137 - 146
• Main Authors: MILES, VICTORIA V., MILES, MARTIN W., JOHANNESSEN, OLA M.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01-02-2016
• Subjects: glacier fluctuations; calving; Arctic glaciology; Greenland
• ISSN: 0022-1430; 1727-5652
• DOI: 10.1017/jog.2016.24

Rapid changes in Helheim Glacier and other Greenland outlet glaciers since 2000 are well-known, but knowledge on earlier decades is fragmentary. Here we exploit the satellite image archives to produce and analyze a monthly-to-seasonal record of Helheim Glacier front position, 1980–2011. Statistical analysis identifies decadal periods with abrupt changes in variability and mean. The record also reveals evidence of volatile advance/retreat behavior in the 1980s. In one of several cases of large-amplitude subannual changes, the glacier front ‘surged’ forward in 1984/85, advancing ~6 km within a few months – surpassing its Little Ice Age maximum position – and afterward retreated ~5 km within a few weeks. These findings challenge the prevailing view of front position stability in the decades before the multi-year retreat in the early 2000s. Cold conditions including rigid ice mélange appear to be a factor in the high-amplitude seasonal advances in the 1980s. However the magnitude and abruptness of the changes in the record cannot be explained solely as a climatic response, such that glacio-dynamics must be invoked. Further, the volatile advance/retreat behavior in the cold 1980s resulted in increased dynamic ice loss, complicating the interpretation of increased calving activity as a response to warming.