Seasonal and Interannual Glacier Terminus Fluctuations in Northwest Greenland and Links to Sea Ice and Velocity Trends during the 21st Century

Abstract:

Current ice loss from the Greenland Ice Sheet is a significant component of global sea-level rise. Observations suggest that both increasing ice flow speeds and sustained terminus retreat on most Greenland glaciers have increased mass loss via ice discharge over the last several decades. However, our understanding of the mechanisms causing retreat and how well connected terminus fluctuations are to other dynamic changes in the ice sheet remains limited. We examined terminus position, sea ice and ice mélange conditions, and seasonal velocity patterns for 16 northwestern glaciers during 2009-2012, with extended 1999-2012 records for 4 glaciers. On a seasonal scale, there is strong correspondence between terminus advance and retreat and sea ice/ice mélange conditions, with a distinct seasonal signature. Longer sea-ice-free periods and reductions in rigid mélange formation appear to induce sustained multi-year retreat outside of the seasonal signal. While seasonal terminus retreat is not clearly linked to seasonal velocity patterns, multi-year retreat is accompanied by interannual speedup on most glaciers. Projections of continued warming and longer sea-ice-free periods around Greenland indicate that notable retreat over wide areas may continue. This sustained retreat likely will contribute to multi-year speedup. Longer melt seasons and earlier breakup of mélange may also alter the timing of seasonal ice-dynamic patterns.