In the next century, 2014 might be one of those years that will live in infamy – the first time in the history of the world that the great ice sheet of West Antarctica was destabilized for good – allowing sea levels to eventually rise as high as 10 feet. You might think that’s a tough act to follow – but 2015 brings even more bad news for the poles north and south of the Equator.
Not only is a massive glacier in East Antarctica in rapid decline, but those living in the northern hemisphere will feel the impact the most heavily due to gravity. The Totten Glacier of East Antarctica drains northeastward towards Australia, and is currently the fastest thinning sector of what is the largest sheet of ice in the world.
A newly published paper in Nature Geoscience, written by an international team of scientists from the United States, Britain, France and Australia, investigates the problem in depth. To gather their data, they have flown several research flights over Totten Glacier, and made several in-depth measurements to find out the precise reason for this shrinkage. So, the verdict? It turns out that warm ocean water is seeping beneath the sheet, causing its decline.
“The idea of warm ocean water eroding the ice in West Antarctica, what we’re finding is that may well be applicable in East Antarctica as well,” says Martin Siegert, of the Grantham Institute at Imperial College London who co-authored the paper.
The glacier’s floating ice shelf of the Totten Glacier covers an area – 90 miles (the length of Maryland) by 22 miles. While Antarctica may be home to about 90 percent of the world’s ice. The amount it is rapidly losing is a volume of ice the “equivalent to 100 times the volume of Sydney Harbour every year,” said the Australian Antarctic Division.
This means that were the glacier to melt away completely, sea levels in Australia could potentially see a rise over 11 feet — comparable to the loss as the West Antarctica ice sheet thins. And that may be the tip of the iceberg. It’s actually “a conservative lower limit,” according to the study’s lead author Jamie Greenbaum, a Ph.D candidate at the University of Texas at Austin.
The Totten Glacier’s decline may be very similar to the West Antarctic glaciers, all of which contain prominent ice shelves sloping out from of the ice on land and then reach into the water, making them vulnerable to rising ocean temperatures. Ocean water comes under the slopes and gradually works on the core, allowing the ice sheet to quickly come loose.
The researchers took three different kinds of measurements on their flights — gravitational measurements alongside both radar and laser altimetry — allowing them to predict what would occur below such a massive glacier. Ice shelves in the Totten Glacier can get to be over 1,600 feet thick in some places. With radar, they were able to determine the ice’s thickness. As they calculated the pull from Earth’s gravity against the airplane as they flew overhead, the scientists were able to fully determine the distance of the ice from the seafloor.
They discovered the presence of what were two undersea troughs beneath the ice, or oceanic valleys, where the seafloor dips downward, acting as a sink basin for greater depths of water beneath the ice shelf, cavities where warmer waters can increasingly build up and speed up the melting process.
In East Antarctica, according to Greenbaum, a warmer layers of ocean water offshore are in fact deeper than the colder layers stacked above, due to salt in the warm water which also makes it more dense. The ocean’s canyons also allow the water to run right up to the base of the ice sheet. “What we found here is that there are seafloor valleys deeper than the depth of the maximum temperature measured near the glacier,” said Greenbaum.
One of these canyons is three miles wide below the sea, across a region that many oceanographers believed had functioned solely to hold down the ice lying on solid earth. Instead, much of this ice is already afloat.
The nature of ice depreciation and abundance of warm water both lend support to the idea that “the behaviour of Totten Glacier is an East Antarctic analogue to ocean-driven retreat underway in the West Antarctic Ice Sheet (WAIS),” according to the paper. “The global sea level potential of 3.5 m flowing through Totten Glacier alone is of similar magnitude to the entire probable contribution of the WAIS.”
While it’s true that Antarctica is tucked far away and has no permanent residents, aside from a few thousand researchers staying at any given time of the year, that hardly means that we won’t be feeling the loss. Volumes of ice lost in Antarctica mean major sea level rises, with the United States alone enduring a rise that’s 25 percent over the global average. Why wouldn’t the loss of ice happen evenly? The answer is gravity. Because the Antarctic continent is so gigantic, it will drag the surrounding ocean towards it. If it no longer has that ice over its landmass, the gravitational pull becomes weak, bringing the ocean waters further back, into the Northern Hemisphere where sea level rises will continue to increase.
Just as the glaciers of West Antarctica have retreated under us doesn’t of course mean that we’ll witness anything like an 11 foot sea rise in our lifetimes. The processes covered by the paper could take centuries or longer to play out. However, even if we successfully do reduce CO2 levels in the atmosphere, the sea will continue to rise, leaving a significant problem for future generations to contend with – ones that could significantly reshape our Earth to levels not seen since the Pliocene Era, two to five million years ago, in which sea levels were 80 feet higher than they were today.