The Greenland Ice Sheet is melting, there’s no doubt about that. A new study funded by NASA and published last week in the journal Science found that the Zachariae Isstrom glacier in northeast Greenland broke loose from its glaciologically stable position in 2012 and the glacier has entered a phase of accelerated retreat. According to NASA, the consequences of this glacier melting will be felt for decades to come.
The Greenland Ice Sheet is made up of a number of glaciers similar to Zachariae Isstrom. The Ice Sheet started forming more than a hundred thousand years ago when snow first began falling over Greenland, the largest island on earth. Because the arctic temperatures in Greenland stayed low enough, the snow didn’t melt. The cold lasted all spring, summer fall and into the next winter, which brought even more snow that didn’t melt. The snow piled up for centuries, even millennia, until eventually the snow turned into a sheet of ice. The Greenland Ice Sheet is a huge blanket of ice covering an area of 650,000 square miles, which is 78% of Greenland. At some places, the thickness of the ice sheet has been measured as 10,000 feet thick.
The Zachariae Isstrom glacier is so huge that 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. The ice in the Zachariae Isstrom glacier holds so much water that if the glacier were to melt completely, the water released by this one melting glacier would raise global sea level by more than 18 inches (0.5-meters). NASA reports that all of that ice is crumbling away and falling into the North Atlantic Ocean.
The lead author of the study, Jeremie Mouginot, puts it this way. “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.”
According to the study, the Zachariæ Isstrøm glacier entered a phase of accelerated retreat in fall 2012, and “the acceleration rate of its ice velocity tripled, melting of its residual ice shelf and thinning of its grounded portion doubled, and calving is now occurring at its grounding line.”
The study found that a combination of warmer air and warmer ocean temperatures caused the Zachariæ Isstrøm glacier to detach from its stabilizing sill and now the glacier is retreating rapidly along its downward-sloping, marine-based bed. For the first time in history, the Zachariæ Isstrøm glacier is not attached firmly to the earth, and the entire huge mass of ice is moving across Greenland and toward the sea.
The study also found that Zachariae Isstrom. Is not the only Greenland glacier melting at an unprecedented rate. Another huge glacier nearby, Nioghalvfjerdsfjorden, has an ice-volume almost equal to the ice volume of Zachariae Isstrom. The NASA research shows that Nioghalvfjerdsfjorden is also melting rapidly but that it is retreating slowly because it is moving along an upward-sloping bed.
Eric Rignot, the study’s senior author said this about the situation. “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.”
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 Zachariae Isstrom and Nioghalvfjerdsfjorden glaciers make up 12 percent of the Greenland Ice Sheet. If they fully collapse, it would raise the global sea levels by more than 39 inches (1 meter). The Greenland Ice Sheet is melting at an alarming rate because of global warming. If it keeps melting at the current rate, it will cause a drastic rise in the sea level that will flood many of America’s most populated areas including Miami, Boston, New York City and other coastal cities.
The scientists studying the Zachariae Isstrom glacier used data from aerial surveys conducted by NASA’s Operation IceBridge and satellite-based observations acquired by multiple international space agencies. The NASA satellite data came from the joint NASA/USGS Landsat program. The scientists used various tools to study the glacier; including a highly sensitive radar sounder, a gravimeter and a laser profiling systems, as well as radar and optical images from space. The precise data from these instruments and satellites enabled the scientists to monitor and record the changes in the shape, size and position of the glacial ice over long periods of time.
Using this data, the scientists were able to determine that the bottom of the Zachariae Isstrom glacier is being eroded rapidly by warmer ocean water mixed with growing amounts of meltwater from the surface of the ice sheet. The study’s senior author Eric Rignot said, “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.”
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. CBS News reports that, “Republicans, including most of the GOP’s 2016 presidential candidates, either don’t acknowledge climate change is happening, or they question whether it’s caused by human activity.” Maybe it’s time for them to accept reality. If the NASA report on the melting the Zachariae Isstrom glacier doesn’t open their eyes, maybe the Oceans Melting Greenland campaign will