July 9, 2018 at 2:27 PM
An enormous, four-mile-long iceberg break, or “calving” event, swept across Greenland’s massive Helheim Glacier last month, a new video has revealed.
The event, in which roughly half-mile-high columns of ice break free and tip onto their backs — and later collide downstream and shatter further — was filmed by Denise Holland, the field and logistics manager for New York University’s Environmental Fluid Dynamics Laboratory and NYU Abu Dhabi’s Center for Global Sea Level Change. The event took about 30 minutes. The video above has been sped up to capture the entire event in under two minutes.
During the summer in Greenland, breaks from glaciers are common but rarely so large. According to NYU, the area of floating ice created here “would stretch from Lower Manhattan up to Midtown in New York City.”
The total amount of ice that fell into the ocean was about 10 billion tons, as the break rippled across the entirety of the glacier’s ice face in half-mile-deep water, said David Holland, a glaciologist at NYU’s Courant Institute of Mathematics and NYU Abu Dhabi, and head of the research team.
“It’s a complete scene of chaos from berg formation,” David Holland said. “Everything possible to happen happened.”
The video captures two types of iceberg creation. First, already-floating parts of the glacier detach and drift away. Next, thicker sections of the glacier that are resting on the seafloor detach, lift up and tip backward as they float to the surface.
Helheim Glacier, one of the largest ice streams flowing from the Greenland ice sheet into the ocean, extends almost 100 yards above sea level at its front. But that’s just a tiny fraction of the glacier’s full vertical extent. The large majority of the glacier front is submerged.
The fjord in which the glacier rests is about 2,000 to 3,000 feet deep, and the deeper water is warmer than the water at the surface. This undermines the glacier at its lowest point, driving fast retreat.
The current break, at about 10 billion tons, represents just over 3 percent of Greenland’s annual ice loss of 286 billion tons, the cumulative result of many losses like this one across many glaciers (as well as large volumes of meltwater spilling directly into the ocean). Each break of 1 billion tons or more is such a massive event that it can create “icequakes” that can be detected far away, as the tipping ice crashes back against the still-attached parts of the glacier.
The researchers are collecting field data on these kinds of events to try to draw conclusions that will be applicable to the much larger, and harder to study, Antarctic. In the Antarctic, ice loss has the potential to be far worse — imagine a similar break across the front of the 75-mile-wide Thwaites Glacier, as opposed to the 4.5-mile-wide Helheim — but will be driven by similar dynamics.
“The better we understand what’s going on means we can create more accurate simulations to help predict and plan for climate change,” Denise Holland said in a statement.