Satellite archives reveal abrupt changes in behavior of Helheim Glacier at Greenland

A new publication in Journal of Glaciology reveals the importance of internal dynamical process in the abrupt changes of the Helheim and other glaciers at Greenland during the last 35 years. Nansen Center and Bjerknes Center scientists Victoria Miles, Martin Miles and Ola M. Johannessen have published the paper Satellite archives reveal abrupt changes in behavior of Helheim Glacier, southeast Greenland.

Comparison of the rapid advance/retreat 1984/85 with the multi-year retreat in the early 2000s. Landsat image from September 1986, overlain with two sets of curves. The solid red curves show positions during the advance in 1984/85 and retreat in 1985/86, labeled in white text. The dotted red curves show the yearly position for Helheim during the retreat in the early 2000s, labeled in black text. The blue dotted curve is the Little Ice Age (LIA) maximum (Khan and others, 2014). The blue arrows indicate the mean position during the stable periods 1991–2001 (S1) and 2006 onwards (S2).The paper addresses the observed rapid changes in Helheim Glacier and other Greenland outlet glaciers during the decades prior to year 2000, a period that is only fragmentary studied. The scientists have exploited the satellite image archives to produce and analyze a monthly-to-seasonal record of Helheim Glacier front position from 1980 to 2011. Statistical analysis identifies decadal periods with abrupt changes in variability and mean of the glacier front location. The study 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 new 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 observed 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.

The publication have been supported with funding from the Trond Mohn Donation to the Nansen Center and the Centre for Climate Dynamics at the Bjerknes Centre through the SEALEV and MARGINS projects, as well as the Research Council of Norway through the EASTGREEN project.

 

Reference: VICTORIA V. MILES, MARTIN W. MILES and OLA M. JOHANNESSEN Satellite archives reveal abrupt changes in behavior of Helheim Glacier, southeast Greenland. Journal of Glaciology, Available on CJO 2016 doi:10.1017/jog.2016.24

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