5 Percent Greenland Ice Sheet Loss as Zachariae Isstrom Glacier Melts

Summary: Melting of Zachariae Isstrom glacier's ice drainage area accounts for a 5 percent Greenland Ice Sheet loss, according to a study in Nov. 12's Science.

aerial photo of all of lower Zachariae Isstrom glacier taken Sept. 30, 2015, from aboard NASA Falcon jet: John Sonntag/NASA Wallops Flight Facility, Public Domain, via NASA Global Climate Change

A NASA-funded study published Nov. 12, 2015, in Science finds rising air and sea temperatures of global warming are shaving 5 billion tons of ice yearly from Zachariae Isstrom, a major northeastern Greenland glacier with the melt potential for 18-inch global sea level rises.

With an ice drainage area of 35,440 square miles (91,780 square kilometers), Zachariae Isstrom glacier accounts for about 5 percent of the Greenland Ice Sheet. Global warming is launching a two-pronged attack against the massive glacier, with rising air temperatures turning surface ice into meltwater and rising ocean temperatures eroding the glacial bottom.

“Zachariae Isstrom is being hit from above and below. The top of the glacier is melting away as a result of decades of steadily increasing air temperatures, while its underside is compromised by currents carrying warmer ocean water, and the glacier is now breaking away into bits and pieces and retreating into deeper ground,” explains Eric Rignot, the study’s senior author, Chancellor’s Professor of Earth System Science at University of California, Irvine (UCI), and joint faculty appointee at NASA’s Jet Propulsion Laboratory.

Two climate feedbacks that are registering prophetically worrisome data are albedo-melt and temperature-elevation. Albedo-melt concerns the darkness or whiteness (Latin: albedo) of the ice sheet. Global warming increases ice sheet melting in a viciously accelerated cycle of greater thawing from greater absorption of solar radiation by ever-darkening ice sheets, dirtied with windblown dust and other less reflective particles. Temperature-elevation reflects the relationship of warmer temperatures to lower elevations. Increased melting from increased absorption of solar radiation is dropping Greenland’s darkened ice sheet to increasingly lower elevations.

Lead author Jeremie Mouginot, an assistant researcher in University of California, Irvine’s Department of Earth System Science, notes: “North Greenland glaciers are changing rapidly. The shape and dynamics of Zachariae Isstrom have changed dramatically over the last few years. The glacier is now breaking up and calving high volumes of icebergs into the ocean, which will result in rising sea levels for decades to come.”

Zachariae Isstrom and its larger but slower neighbor, Nioghalvfjerdsfjorden glacier, make up 12 percent of Greenland’s millennially-aged ice sheet. Although Nioghalvfjerdsfjorden shows a rapid melt rate, an upward-sloping bed slows the glacier’s rate of retreat. The combined melt potential of full collapse by both glaciers could produce a global sea level rise of more than 39 inches (99 centimeters).

The unknown rate of calving, or of a glacier’s breakup into icebergs, and the inherent unpredictability of marine-terminating glaciers complicate timelines for Zachariae Isstrom’s complete collapse.

As marine-terminating glaciers that send ice sheet-edged ice flows into the Greenland Sea, Zachariae Isstrom and Nioghalvfjerdsfjorden are sited in one of Greenland’s three major marine-based basins. The future full collapse of Petermann-Humboldt in central north Greenland and Jakobshavn Isbrae glacier in the central west sector could boost global sea levels by 2 feet (0.6 meters).

Eric Rignot emphasizes: “Not long ago, we wondered about the effect on sea levels if Earth’s major glaciers in the polar regions were to start retreating. We no longer need to wonder; for a couple of decades now, we’ve been able to directly observe the results of climate warming on polar glaciers. The changes are staggering and are now affecting the four corners of Greenland.”

Landsat-8 image of Zachariae Isstrom and Nioghalvfjerdsfjorden glaciers, acquired Aug. 30, 2014: NASA/USGS, Public Domain, via NASA Global Climate Change

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Zachariae Isstrøm: John Sonntag/NASA Wallops Flight Facility, Public Domain, via NASA Global Climate Change @ http://climate.nasa.gov/news/2366/

Landsat-8 image of Zachariae Isstrom and Nioghalvfjerdsfjorden glaciers, acquired Aug. 30, 2014: NASA/USGS, Public Domain, via NASA Global Climate Change @ http://climate.nasa.gov/news/2366/

For further information:

Bell, Brian. "Massive northeast Greenland glacier is rapidly melting, UCI-led team finds." UCI News > Faculty. Nov. 12, 2015.
Available @ http://news.uci.edu/research/massive-northeast-greenland-glacier-is-rapidly-melting-uci-led-team-finds/

Gertner, Jon. "The Secrets in Greenland's Ice Sheet." The New York Times Magazine. Nov. 12, 2015.
Available @ http://www.nytimes.com/2015/11/15/magazine/the-secrets-in-greenlands-ice-sheets.html?_r=1

"In Greenland, another major glacier comes undone." NASA Jet Propulsion Laboratory. Nov. 12, 2015.
Available @ http://www.jpl.nasa.gov/news/news.php?feature=4771
Available @ http://climate.nasa.gov/news/2366/

Lindsey, Rebecca. "Greenland Ice Sheet Getting Darker." NOAA Climate.gov > News & Features > Understanding Climate.
Available @ https://www.climate.gov/news-features/understanding-climate/greenland-ice-sheet-getting-darker

Mouginot, J., et al. "Fast retreat of Zachariae Isstrøm, northeast Greenland." Science. Nov. 12, 2015. DOI: 10.1126/science.aac7111
Available @ http://www.sciencemag.org/content/early/2015/11/11/science.aac7111.full

NASA Climate Change. "NASA's Earth Minute: Greenland Ice." YouTube. Aug. 28, 2015.
Available @ http://www.youtube.com/watch?v=yLm7PSsvW8g

NASA JPL‏ @NASAJPL. "It's big. It's cold. It's melting. Another major Greenland glacier comes undone." Twitter. Nov. 12, 2015.
Available @ https://twitter.com/NASAJPL/status/664946045625827328