The Larsen C rift.

Photo Courtesy of John Sonntag

The Larsen C Calving: The Tip of the Iceberg

By Olivia Williams           November 25, 2017

Much of the public was appalled to hear that an iceberg approximately the size of Delaware had broken free from Antarctica’s Larsen C ice shelf this July. News outlets hailed this as evidence of humanity’s irreparable impact on the environment—a sudden and apocalyptic warning which some claimed would lead to immediately measurable sea rise. However, the real ramifications of Larsen C’s breakup are much more nuanced.

Scientists who study Antarctic ice have been aware of the crack in Larsen C since it first appeared decades ago, and have been monitoring its accelerated growth since 2014. This event was neither sudden nor unexpected for those in the field, although news coverage made it sound as though the situation developed in a matter of weeks or months.

It’s difficult to directly tie Larsen C’s disintegration to climate change. As much as we should be worried about the glaciers around the globe melting at an alarming rate, this particular event, while above average in magnitude, seems to have been a part of natural ice shelf activity. Throughout the year, it’s usual for ice to melt and break off from Antarctica’s ice masses, only to be replaced later by snow accumulation. That’s not to say that this breakup couldn’t have been accelerated by climate change—just that scientists don’t have enough data to suggest that it could have been avoided by reducing our environmental impact. Besides, even if this event is part of natural cycles, other Antarctic ice is showing observable melting as oceans and the atmosphere warm.

The Larsen C calving will not cause immediate sea level rise. Unlike an ice sheet, which is based on land, ice shelves are already floating on water. Due to the physical properties of water, the breakup and subsequent melting of floating ice will not be the direct cause of any increase in sea level. However, natural events do not happen in a vacuum; everything is part of a system, and every system is interconnected with dozens of others.

Antarctica’s ice shelves act as something of a buffer for its ice sheets. If calving events of this magnitude become more common as the poles warm, annual snowfall may not be adequate to keep ice shelves in balance (the main measure of the health of an ice system), and without ice shelves insulating it, Antarctica’s land-based ice could begin to melt at an accelerated rate.

The Ross Ice Shelf, for example, is a large stretch of sea-based ice with McMurdo Station on its edge. It seems to be stable for now, though even that is up for debate. The Ross Ice Shelf acts as a stopper that prevents the West Antarctic glaciers that are behind it from flowing down towards the sea. If it were to melt, there would be nothing acting as a barrier between those glaciers and the ocean.

Sean Mackay, a glaciologist and member of  Boston University’s Antarctic Research Group, explains in an interview with BU Research: “…when these ice shelves start to disintegrate, and especially if they disintegrate beyond… a point of no return, then those glaciers can flow more easily. And from the previous collapse of the Larsen A and the Larsen B ice shelves, we’ve been able to see firsthand—and directly measure—how quickly the upstream glaciers have accelerated. And it’s a lot.” The upstream glaciers that Mackay refers to will raise sea level if they melt.

If the West Antarctic Ice Sheet melts, it is predicted that the mean sea level could rise by up to ten feet. In Boston, this would leave a few neighborhoods as islands while Back Bay, the South End, and other lowland areas would be underwater. Over 100,000 Boston residents could be displaced by sea level rise of this magnitude.  Across the US, 28,800 square miles of land would be lost to flooding.

The ground on which the West Antarctic Ice Sheet rests is below sea level. For this reason, the ice is extremely vulnerable to sea temperature fluctuations. If the floating ice around this ice sheet breaks up, nothing will be left to insulate it from warming waters. Even if protective barriers like the Ross Ice Shelf remain in place, it may be possible for warm water to seep underneath and begin melting the ice from below. The collapse of the West Antarctic Ice Sheet wouldn’t be instantaneous, but it is possible for it to get well underway within the next several decades.

The Antarctic system and its balances are not especially well understood. Much of the current research in Antarctica is attempting to determine just how stable its ice sheets are by studying past climate trends and the accompanying changes in ice coverage. When it comes to the question of how warm is too warm, the answer is simple: we don’t have enough information to know yet, but if we don’t start drastically reducing our carbon emissions, we may find out the hard way.

It’s irresponsible to point to the Larsen C calving as some sort of distress flare sent up by Mother Nature, but it is essential that we turn our attention to the health of the Antarctic system and consider how our actions impact ice worldwide in the long term. It’s not too late to avoid the most drastic sea level rise as long as we don’t succumb to denial or despair. Instead, let this dramatic event draw interest to ice preservation around the world and spur policy aimed at protecting it as we move forward.



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