Study tracks rapid retreat of major ice streams
Scientists may not have to wait too much longer to observe firsthand the effects of global warming on Greenland’s ice sheets. One of the largest glaciers in Greenland entered “a phase of accelerated retreat in 2012,” and may be near a climate tipping point, according to new research published in the current issue of Science.
After studying the Zachariae Isstrom, scientists with the University of California, Irvine, said it’s starting to break up.
“North Greenland glaciers are changing rapidly,” said Jeremie Mouginot, an assistant researcher with UCI’s department of earth system science. “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 used data from aerial surveys and satellite-based observations acquired by multiple international space agencies.
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 bottom of Zachariae Isstrom is being rapidly eroded by warmer ocean water mixed with growing amounts of meltwater from the ice sheet surface, the researchers explained.
“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 ice researcher Eric Rignot. “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, the 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.”