Hidden Risks in a Warming Antarctic

By Nathaniel Scharping | June 3, 2016 10:42 am
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(Credit: Photodynamic/Shutterstock)

As the rest of the world heats up and the Arctic hemorrhages ice, a different story is playing out in Antarctica. Total ice coverage there has actually increased, and temperatures have risen only mildly. As researchers have attempted to adequately model the changing climate, the Antarctic paradox has served as ammunition for climate change deniers and challenged climate scientists.

But three recently published papers help explain why the Antarctic isn’t falling in line with the rest of the world, while highlighting an overlooked trend in Antarctic sea ice.

Surrounded by Cold Water

One reason Antarctica has remained cold is due to the presence of the Antarctic Circumpolar Current (ACC), a wide band of slow-moving cold water that completely encircles the continent.

The current keeps out warmer water that has driven changes in the northern hemisphere, and preserves Antarctica’s vast shelves of floating sea ice. As a team of researchers from MIT and the University of Washington explain in a paper published in Nature Geoscience in May, global currents pull warm surface water away from Antarctica while frigid flows of centuries-old water from the deep rises to the surface — the last time this water reached the surface was before the age of machines. These currents move slowly, so this deep, cold water could potentially feed the ACC for centuries to come, they say.

Even behind the buffer zone of the ACC, climatic mechanisms are acting to shore up Antarctica’s ice. The natural topography of the continent creates icy winds that blow from the interior of the continent outward. Combined with currents near the shore, the winds concentrate sea ice in what researchers call the “Great Shield,” where older, more resilient sea ice forms a barrier, allowing younger ice to form closer to shore.

That conclusion comes from NASA researchers who, in a paper published in the journal Remote Sensing of Environment, say the presence of a hardened wall of thick sea ice is creating protected areas, which they call “ice factories”, where ice shelves can form. In these sheltered areas, ice can form up to ten times faster, creating ice shelves that replace open water. In addition, other researchers have argued that a lower concentration of salty water at the surface in the Antarctic,  a result of increased precipitation, has bolstered ice formation in the region, as it freezes more readily.

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(Credit: Bernhard Staehli/Shutterstock)

Not So Rosy After All

While Antarctica may appear to buck the trend of warming and sea level rise, a problem may be lurking beneath the surface.

Scientists at the University of Edinburgh in the U.K. in May published a paper in Geophysical Research Letters reviewing satellite data from Antarctica over the past 40 years. They peered beneath the continent’s glaciers to examine what’s known as the “grounding line”, or the point beneath the ocean where glaciers are no longer attached to the ground and float freely as ice shelves.

The researchers used the movement of grounding lines as proxies for the mass of the ice sheets — the further offshore a grounding line is located, the more weight is required to keep it pushed firmly to the ground. They looked at the Bellingshausen Sea in West Antarctica and found a consistent pattern of retreat in the grounding line, an indication that the ice sheet was losing mass. And the process speeds up as the ice shelves get smaller, rendering them unable to hold back the mass of ice packed up on land behind them. The massive glaciers currently held in place by the ice shelves could all wind up in the ocean, introducing hundreds of thousands of square miles of ice into the sea.

While the researchers looked at only one glacier, the same process could be happening to ice shelves around the continent. What’s more, the researchers fear that an area called the Venable Ice Shelf could be susceptible to the same fate as nearby Pine Island Glacier. That ice mass rests atop a large trench, which was gradually exposed as it was pushed backwards.

When the sea finally breached the trench, it rushed in and sealed the glaciers fate. The presence of a large body of warm water underneath the ice destroyed the glacier from below. They believe that Venable covers a similar formation, and if the trench is opened to the sea, a slow retreat could turn into a full-scale rout.

CATEGORIZED UNDER: Environment, top posts
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  • John C

    If we really don’t understand what’s happening with global climate today, as in Antarctica, it seems kind of presumptuous to confidently make predictions a century or more out.

    • OWilson

      Shhhhhhh!

  • OWilson

    So the Antarctic ice is growing, but if you are an AGWer, somebody will come along and sell you a cheap explanation to make you feel good.

    There’s a Huuuuge market for snake oil.

    As P.T. Barnum said, there’s a sucker born every minute

  • http://www.mazepath.com/uncleal/qz4.htm Uncle Al

    The ice Age never left Antarctica, for it is a plop of land entirely surrounded by vast ocean and Ekman transport. Everything else is ocean surrounded by land enjoying an interglacial warming period. OH! for planet Earth rejoining Jamestown frozen out at -40° in 1610, 26 miles up a Virginia estuary, or cutting 3-foot thick blocks of Hudson River ice in the early 1900s.

    Youtube v=QVuU2YCwHjw Any curve can be parameterized into a fitted curve whose predictions are irrelevant to the next point. Wolfram Alpha has curve fits for Batman, Iron Man, Thor, the Hulk, Captain America, Spiderman, Naruto, Ronald MacDonald, Gandhi, Obama…all of them with higher fidelity than Klimate Kaos. To where did the hockey stick vanish?

  • zlop

    Pushing out, isolating from other circulations, there is the Antarctic Vortex, which sucks in air at a higher potential temperature. At about 280 hPa, the Potential Temperature is equal, globally.

  • Ches Easton

    Must be uncovering some amazing things we would not otherwise have access to.

  • Mike Richardson

    Satellite data, particularly from NASA’s GRACE satellite survey, do indeed show loss of ice mass in Antarctica, regardless of ice coverage. This mass loss is what’s most concerning, and if Antarctica’s feedback mechanisms are overcome by melt and ungrounding from below, it could duplicate the accelerated glacier movement seen in Greenland. Ice coverage is in this case, only the tip of the iceberg.

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