Landsat-8 image of Greenland's Zachariae Isstrom and Nioghalvfjerdsfjorden glaciers, acquired on 30 August 2014. Photo: NASA / USGS

12 November 2015 (NASA) – It's big. It's cold. And it's melting into the world’s ocean.

It's Zachariae Isstrom, the latest in a string of Greenland glaciers to undergo rapid change in our warming world. A new NASA-funded study published today in the journal Science finds that Zachariae Isstrom broke loose from a glaciologically stable position in 2012 and entered a phase of accelerated retreat. The consequences will be felt for decades to come.

The reason? Zachariae Isstrom is big. It drains ice from an area of 35,440 square miles (91,780 square kilometers). That’s about 5 percent of the Greenland Ice Sheet. All by itself, it holds enough water to raise global sea level by more than 18 inches (46 centimeters) if it were to melt completely. And now it's on a crash diet, losing 5 billion tons of mass every year. All that ice is crumbling into the North Atlantic Ocean.

“North Greenland glaciers are changing rapidly,” said lead author Jeremie Mouginot, an assistant researcher in the Department of Earth System Science at the University of California, Irvine. “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.”

Mouginot and his colleagues from NASA's Jet Propulsion Laboratory, Pasadena, California; and the University of Kansas, Lawrence, set out to study the changes taking place at Zachariae Isstrom.

The team used data from aerial surveys conducted by NASA’s Operation IceBridge and satellite-based observations acquired by multiple international space agencies (NASA, ESA, CSA, DLR, JAXA and ASI) coordinated by the Polar Space Task Group. The NASA satellite data used are from the joint NASA/USGS Landsat program. The various tools used — including a highly sensitive radar sounder, gravimeter and laser profiling systems, coupled with radar and optical images from space — monitor and record changes in the shape, size and position of glacial ice over long time periods, providing precise data on the state of Earth’s polar regions.

The scientists determined the bottom of Zachariae Isstrom is being rapidly eroded by warmer ocean water mixed with growing amounts of meltwater from the ice sheet surface. “Ocean warming has likely played a major role in triggering [the glacier’s] retreat,” Mouginot said, “but we need more oceanographic observations in this critical sector of Greenland to determine its future.”

“Zachariae Isstrom is being hit from above and below,” said the study’s senior author Eric Rignot, Chancellor’s Professor of Earth system science at UCI, and Joint Faculty Appointee at JPL. “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.”

Adjacent to Zachariae Isstrom is another large glacier, Nioghalvfjerdsfjorden, which is also melting rapidly but is receding at a slower rate because it’s protected by an inland hill. The two glaciers make up 12 percent of the Greenland ice sheet and would boost global sea levels by more than 39 inches (99 centimeters) if they fully collapsed.

The sector where these two glaciers reside is one of three major marine-based basins in Greenland, along with Jakobshavn Isbrae in central west Greenland and the Petermann-Humboldt sector in central north Greenland. The latter two sectors hold enough water to raise global sea level by 2 feet (0.6 meters) each, and both are also undergoing significant changes at present. The authors conclude it is likely that Nioghalvfjerdsfjorden and Petermann-Humboldt glaciers will lose their ice shelves in coming years, further increasing Greenland’s future contributions to global sea level rise.

“Not long ago, we wondered about the effect on sea levels if Earth’s major glaciers in the polar regions were to start retreating,” Rignot noted. “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.”

In 2015, NASA kicked off a new six-year field campaign, Oceans Melting Greenland, which will examine ocean conditions around Greenland affecting the Ice Sheet. For more information on OMG, visit https://omg.jpl.nasa.gov/portal/.

Ongoing research into the health of ice sheets and glaciers in Greenland and Antarctica is supported by funding from NASA’s Cryospheric Sciences Program.

For more information on the study, see Massive northeast Greenland glacier is rapidly melting, UCI-led team finds.

In Greenland, another major glacier comes undone


Image time series of Greenland's Zachariæ Isstrøm glacier as seen by the NASA/USGS Landsat satellite. Retreat of the glacier front is indicated by lines, color-coded from dark green (2003) to light green (2015). Photo: NASA / USGS

Irvine, California, 12 November 2015 – A glacier in northeast Greenland that holds enough water to raise global sea levels by more than 18 inches has come unmoored from a stabilizing sill and is crumbling into the North Atlantic Ocean. Losing mass at a rate of 5 billion tons per year, glacier Zachariae Isstrom entered a phase of accelerated retreat in 2012, according to findings published in the current issue of Science.

“North Greenland glaciers are changing rapidly,” said lead author Jeremie Mouginot, an associate project scientist in the Department of Earth System Science at the University of California, Irvine. “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.”

The research team – including scientists from NASA’s Jet Propulsion Laboratory and the University of Kansas – used data from aerial surveys conducted by NASA’s Operation IceBridge and satellite-based observations acquired by multiple international space agencies (NASA, ESA, CSA, DLR, JAXA and ASI) coordinated by the Polar Space Task Group.

The highly sensitive radar sounder, gravimeter, and laser profiling systems, coupled with radar and optical images from space, monitor and record changes in the shape, size and position of glacial ice over long time periods, providing precise data on the state of Earth’s polar regions.

The scientists determined that the bottom of Zachariae Isstrom is being rapidly eroded by warmer ocean water mixed with growing amounts of meltwater from the ice sheet surface. “Ocean warming has likely played a major role in triggering [the glacier’s]retreat,” Mouginot said, “but we need more oceanographic observations in this critical sector of Greenland to determine its future.”

“Zachariae Isstrom is being hit from above and below,” said senior author Eric Rignot, Chancellor’s Professor of Earth system science at UCI. “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.”

Zachariae Isstrom neighbors another large glacier, this one named Nioghalvfjerdsfjorden, that also is melting rapidly but is receding at a slower rate because it’s protected by an inland hill. The two glaciers make up 12 percent of the Greenland ice sheet and would boost global sea levels by more than 39 inches if they fully collapsed.

“Not long ago, we wondered about the effect on sea levels if Earth’s major glaciers were to start retreating,” Rignot noted. “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.”

Ongoing research into the health of ice sheets and glaciers in Greenland and Antarctica is supported by funding from NASA’s Cryospheric Sciences Program.

To see video, photos and a narrative of the August 2014 expedition, visit http://news.uci.edu/greenland.

About the University of California, Irvine: Currently celebrating its 50th anniversary, UCI is the youngest member of the prestigious Association of American Universities. The campus has produced three Nobel laureates and is known for its academic achievement, premier research, innovation and anteater mascot. Led by Chancellor Howard Gillman, UCI has more than 30,000 students and offers 192 degree programs. It’s located in one of the world’s safest and most economically vibrant communities and is Orange County’s second-largest employer, contributing $4.8 billion annually to the local economy. For more on UCI, visit www.uci.edu.

Media access: Radio programs/stations may, for a fee, use an on-campus ISDN line to interview UC Irvine faculty and experts, subject to availability and university approval. For more UC Irvine news, visit news.uci.edu. Additional resources for journalists may be found at communications.uci.edu/for-journalists.

Massive northeast Greenland glacier is rapidly melting, UCI-led team finds

0 comments :

 

Blog Template by Adam Every . Sponsored by Business Web Hosting Reviews