Latitudinal gradients in ice dynamic response: results from satellite remote sensing in East Greenland
- Paper number
IAC-06-B1.5.07
- Author
Ms. Leigh Stearns, University of Maine, United States
- Coauthor
Dr. Gordon Hamilton, University of Maine, United States
- Year
2006
- Abstract
Mass from the interior of the Greenland ice sheet is transported to the ocean by large, fast-flowing outlet glaciers. Changes in the configuration of these outlet glaciers modulate ice sheet mass balance and sea level. Most sea level rise predictions consider the near-term contribution from changes in ice dynamics to be relatively small. We present new ice velocity maps and histories of calving front position for six outlet glaciers in East Greenland. Our results show that the four northern glaciers, located in Scoresby Sund, remained stable for the past ∼40 years, whereas the southern glaciers (Kangerdlussuaq and Helheim glaciers) are undergoing rapid changes in ice dynamics.
High-resolution satellite imagery is used to quantify changes in glacier dynamics. Ice velocity measurements for 2001 and 2005 are obtained by applying a feature tracking technique to sequential high-resolution visible imagery. Displacements of surface features are derived by matching patterns of brightness in two images, acquired several months apart, using an automatic cross-correlation technique. This method yields a dense array of velocity vectors for each glacier. Additional ice velocity measurements for 2005 were obtained from field GPS surveys of five of the glaciers. Calving front positions are reconstructed using aerial photography, Landsat and ASTER imagery.
Our results show a latitudinal gradient in ice dynamic response: the northern glaciers have been stable for ∼50 years, whereas the southern glaciers are undergoing dramatic changes. The calving front positions and ice velocities of the Scoresby Sund glaciers remained remarkably constant since 1960s (based on archival measurements). The southern glaciers, however, have undergone rapid retreat and acceleration. Kangerdlugssuaq and Helheim glaciers, both retreated ∼5 km from 2004 to 2005, after occupying stable terminus positions between 1972 to 2004. Ice velocity results show a similar pattern of response. In 2001 both glaciers sustained maximum velocities of ∼6 km/yr. By 2005 Kangerdlugssuaq Glacier accelerated to ∼14 km/yr and Helheim Glacier accelerated to 11 km/yr.
The rapid acceleration and retreat of the two southern glaciers coupled with the stable behavior of the northern glaciers, suggests a latitudinal triggering mechanism, such as enhanced surface melting due to observed regional climate warming. These results highlight the sensitivity of large outlet glaciers to climate-related perturbations and imply that current estimates for the sea level contribution from the Greenland ice sheet need to be re-evaluated to account for rapid changes in ice dynamics.
- Abstract document
- Manuscript document
IAC-06-B1.5.07.pdf (🔒 authorized access only).
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