A massive iceberg over 100 square miles in size just calved from an enormous Antarctic glacier. The Pine Island Glacier is one of the largest in the area, but it has already lost significant chunks of ice. Now, scientists are wondering whether the glacier’s behavior is taking a turn for the worse.
The Pine Island Glacier is located in West Antarctica, a region that is now Antarctica’s biggest ice loser. Scientists estimate that Pine Island loses about 45 billion tons of ice to the ocean each year, which contributes to 1 millimeter of global sea level rise every 8 years.
Pine Island is 25 miles wide where its front touches the ocean and sits on a seafloor more than half a mile deep. Experts say the Pine Island Glacier contains about 1.7 feet of possible global sea level rise.
Iceberg the size of four Manhattans calved away from Pine Island Glacier on Saturday
The glacier attracts a lot of attention from scientists, due to its potential for massive sea level rise. What’s more, over the last years, the glacier has become more unpredictable and unstable, as icebergs continue to calve from Pine Island.
On Saturday, a satellite observation specialist at the Delft University of Technology in the Netherlands named Stef Lhermitte, took Twitter to post a satellite image showing that the glacier had calved, as a piece of about 103 square miles –more than four times the size of Manhattan—in size broke off from Pine Island.
“It’s the fifth large calving event since 2000,” said Lhermitte on Twitter. “This one and 2015, they were much further inland than the previous ones. So there has been a retreat of the calving front, specifically between 2011 and 2015.”
Last year, a study led by Seongsu Jeong and Ian Howat of Ohio State University found that Pine Island Glacier was “breaking up from the inside out.” The researchers said the ice shelf had developed a new way of losing ice, as rifts were forming in the center of the floating ice shelf from beneath and not from the sides, how it usually occurs.
The researchers suggested that is a function of warmer ocean waters reaching the base of Pine Island Glacier and undermining it.
“We predicted that the rifting would result in more frequent calving, which is what’s happening here,” Howat, a glaciologist at Ohio State, told The Washington Post. “If new rifts continue to form progressively inland, the significance to ice shelf retreat would be high.”
Pine Island Glacier may be retreating inland
Howat warns that’s not the only problem. He said a series of thin cracks were seen in the center of the ice shelf about 3 km inland of the current break six months ago. Howat acknowledged they don’t have any more recent data to see the status of the cracks, but that means another calving event could happen “very soon.”
He noted something similar happened after the 2015 break, a sort of “aftershock” event following a massive calving. The scientist noted that while the current ice loss is not as significant as the loss of an enormous ice island from the Larsen C ice shelf earlier this year, changes in Pine Island Glacier are more consequential in terms of sea level rise.
Experts believe warmer ocean temperatures reaching the “grounding line” –the point where the floating portion of the iceberg touches the seafloor—are responsible for Pine Island Glacier losing so much ice in recent years.
Scientists fear the glacier has entered a process of unstable, runaway retreat. Its grounding line has been shifting inland, and as it continues retreating, the seafloor bed dips downward – which means the ocean becomes even deeper and the ice becomes thicker. So, in other words, if Pine Island Glacier continues retreating, the outward flow will continue increasing, leading to more ice loss and further sea level rise.
‘This results in smaller but more-frequent calving events’
Knut Christianson, a glaciologist at the University of Washington, tells The Washington Post that calving events are quite normal. However, he noted that the mode of calving of Pine Island “appears to be shifting.”
He said that as the latest rift originated in the center of the ice shelf (and not on its sides) could suggest that the rift developed far inland at the grounding line as a result of the warm water hitting the base of the glacier.
“This results in smaller but more-frequent calving events,” said Christianson. “The persistence and net effect of this shift in calving behaviors has yet to be determined as it has only occurred during the past two years, but it clearly merits continued observation.”
Source: The Washington Post