Terminus data for: Multi-decadal retreat of Greenland’s marine-terminating glaciers ...

• Main Authors: Howat, Ian M., Eddy, Alex
• Format: Dataset
• Language: English
• Published: Dryad 2020
• Subjects: marine-terminating glaciers; Greenland; glacier; Ice Sheet
• Online Access: https://dx.doi.org/10.5061/dryad.vhhmgqnq6; https://datadryad.org/stash/dataset/doi:10.5061/dryad.vhhmgqnq6

Many marine-terminating glaciers draining the Greenland ice sheet have retreated over the past decade, yet the extent and magnitude of retreat relative to past variability is unknown. We measure changes in front positions of 210 marine-terminating glaciers using Landsat imagery spanning nearly four decades and compare decadal-scale rates of change with earlier observations. We find that 90% of the observed glaciers retreated between 2000 and 2010, approaching 100% in the northwest, with rapid retreat observed in all sectors of the ice sheet. The current retreat is accelerating and likely began between 1992 and 2000, coincident with the onset of warming, following glacier stability and minor advance during a mid-century cooling period. While it is clear an extensive retreat occurred in the early 20th century, a period of increasing air temperatures, a comparison of our results with historical observations provides evidence that the current retreat is more widespread. The onset of rapid retreat with warming ... : The details are included in the manuscript and elements of the 'Ice-front change mapping' section are copied here, with minor edits: We mapped the change in ice-front position between image pairs using the ‘box method’ of Moon and Joughin (2008) and Howat and others (2010). On each image, we manually digitized (with a computer mouse) the outline of a polygon bounded on the down-glacier edge by the ice front, on each lateral side by parallel lines approximating the glacier margins, and on the upstream side by an arbitrary straight line placed inland of the minimum observed front position. This polygon was overlain on the second image, and the ice-front border of the polygon was adjusted to the new front position. The difference in the area of the polygon between successive images is the area change of the front, and the average retreat distance is obtained by dividing the area of retreat by the polygon width. This procedure yields a less arbitrary measure of front position change than the change along a ...