According to a paper published on 12 November 2015 in Science, yet another major glacier of Greenland has entered a phase of accelerated retreat. According to the paper’s abstract, the Zachariæ Isstrøm glacier in northeast Greenland entered a phase of accelerated retreat in fall 2012. According to lead authors Jeremie Mouginot and Eric Rignot of the University California (Irvine), the massive glacier holds enough frozen water to raise global sea-levels half a meter.
According to the paper’s abstract, “Warmer air and ocean temperatures have caused the glacier to detach from a stabilizing sill and retreat rapidly along a downward-sloping, marine-based bed. Its equal-ice-volume neighbor, Nioghalvfjerdsfjorden, is also melting rapidly but retreating slowly along an upward-sloping bed. The destabilization of this marine-based sector will increase sea-level rise from the Greenland Ice Sheet for decades to come.”
To measure changes in glacial flow for the neighboring glaciers, the researchers constructed a high-resolution bed topography of both glaciers. They used Landsat optical imagery to document the ice front positions over the last 40 years. They found that while the Nioghalvfjerdsfjorden retreated only only a few km between 2002 and 2012, the Zachariæ Isstrøm glacier lost a large section in 2002-03 and the front steadily for a decade until its northern and southern sections became disconnected late in 2012.
“In 2013-2014,” they wrote, “the ice front retreat accelerated markedly and the glacier started to calve at its grounding line. By December 2014, the remaining shelf was 52 km2 in size, or 95% smaller than in 2002.”
“Ice loss is happening fast in glaciological terms, but slow in human terms — not all in one day or one year,” said John Paden, associate scientist for CReSIS and courtesy associate professor of electrical engineering and computer science at KU, who helped analyze data about the thickness of the glacier’s ice for the study.
Paden said the “grounding line,” or the boundary between land and sea underneath a glacier, is a zone of special interest. “The grounding line is where the ice sheet starts to float and is where the ice flux was measured,” Paden said. “The grounding line is a good place to determine thickness across the ice. The terminus of Zachariæ Isstrøm is now at the grounding line —the ocean is right up against the grounded part of the glacier.
Historically, across 40 years, the speed Zachariæ Isstrøm glacier by 50% between 2000-204, with half of that increase occurring after 2012. Because of this, the glacier has “now transformed into a tidewater glacier calving along an ice cliff as a result of warmer air and ocean temperatures.”
These events follow on the tail of a similar rapid retreat by other major marine-based basins in Greenland. According to the authors, “observations suggest that all three major marine-based basins are undergoing significant changes at present.”
They add, “The retreat of these marine-based sectors is likely to increase sea-level rise from Greenland for decades to come.”
To read the original paper, click here.
ECO Magazine published a full feature on the Greenland Ice Melt and what’s being done to measure these types of changes in October 2015. Seeecomagazine.com to subscribe.
