Antarctica Is Covered In Meltwater Rivers That Cause Rising Sea Levels

Much of Antarctica is still a mystery to us. This vast territory is sparsely populated, which means scientists are still discovering new things about it every year. The latest findings are hardly positive. Researchers have observed a surprisingly ample network of meltwater rivers traverses Antarctica’s ice caps, the floating appendices of ice that elongate from the continent’s shorelines.

These periodic flows of waterways are not uncommon. A part of Antarctica’s natural hydrological cycle, they have been cutting across the continent for decades, maybe even centuries. However, now that scientists have methodically cataloged them, the news were surprising. It appears the meltwater rivers are much more vast than scientists had previously expected.

Some of the water systems have achieved incredible scales. For instance, East Antarctica’s Amery Ice Shelf is traversed by streams that carry meltwater up to 120 kilometers. The many ponds on the surface of the ice shelf surface feed off them, which means some are over 80 kilometers long. The largest pond on this particular ice cap has a fantastic drainage. It can increase by over 400 NFL football fields – throughout the course of just one day!

The discoveries were published Wednesday in Nature. According to the new data, Antarctic meltwater doesn’t just pool where it melts (as previous models illustrate). But are these meltwater systems – rising to almost 700 in total – helping or damaging Antarctica’s ice shelves? So far, scientists have no answer for this high-stakes question. But finding out is a priority, given the shelves’ potential role in the rising sea levels.

In Antarctica, it can be hard to tell where the land starts and (frozen) water begins. /
PHOTO BY MARIO TAMA

The Gatekeepers of the Ocean

By definition, melting ice shelves do not affect sea level rise straightforwardly. An ice shelf already floats in water. However, according to Rob DeConto, a climatologist at the University of Massachusetts-Amherst, many ice shelves serve as braces, blocking the flow of ice from land to water. Therefore, the melting of these ice shelves accelerates the seaward flow of the ice caps, essentially turning on a faucet that contribute to raising sea levels.

Co-author Robin Bell, a glaciologist with the Columbia University’s Lamont-Doherty Earth Observatory, made a compelling analogy. The melting ice shelves are like a bouncer that allows floods of party people into a club. If you take away the gatekeepers, more ice makes its way into the waters of the ocean.

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This comparison shows why meltwater rivers can indeed represent a threat for the ice shelves’ resistance. They represent added weight, which encourages the widening of the crevasses within. For example, in the days leading up to the sudden collapse of the Larsen B Ice Shelf in 2002, researchers observed ponds of meltwater were covering its surface. Larsen C, another chunk of the same ice cap, could crumple within months, as well.

In one of their two recent investigations, Bell and co-author Jonathan Kingslake warn meltwater drains on the surface of ice sheets, causing the formation of melt ponds. In turn, they can trigger ice-shelf destruction, increased sea-level rise, and expedition of grounded ice flow. They also worry that substantial drainage could aggravate the threat of meltwater. These streams and flows will allow meltwater to move around even more effectively, particularly if climate change goes on.

A Glimmer of Hope

Bell and Kingslake have also published a second study, which seems to enlighten the ominous predictions a bit. As we said in the introduction, the researchers are still in the dark about whether or not the meltwater rivers help or hurt Antarctica’s ice shelves. According to the second study, these waterway system could be stabilizing ice shelves. At the very least, one of them seems to benefit. What it does is effectively drain meltwater off the ice shelf to ease the strain.

Bell’s research of Antarctica’s Nansen Ice Shelf – a 1,800-square-kilometer ice tongue that extends into the Ross Sea – found the ice shelf has been channeling its meltwater streams into the ocean for the better part of a century. The diverging streams eventually join, draining the meltwater into the ocean through a 130-meter-wide waterfall.

The proportions of this river on ice are hard to fathom. Bell discovered that even on the low end, the large waterway moves enough water to compare to the size of the Potomac River in the U.S. And none of these continent-wide discoveries would have been possible without the data collected over the past few decades. Bell added their findings rely on thousands of satellite photos, as well as imagery provided by military aircraft.

Meanwhile, Bell’s extensive analysis of the Nansen Ice Shelf was possible due to the old journals kept by the Northern Party. A detachment of Sir Robert Scott’s doomed Terra Nova expedition, the Northern Party never got to venture into the South Pole. In spite of the many useful measurements they left behind, people only remember them by one thing. The team was stuck and forced to winter in a cave, instead of measuring the terrain. Bell, however, stated it was an immense joy to use the Northern Party’s science and give them credit for their work.

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Terra Incognita

Kingslake and Bell, as well as outside experts, agree that much more of Antarctica remains in a shroud of secrecy. The continent is a forbidding territory that reluctantly reveals its mysteries to scientists and scientific tools. Helen Fricker, a glaciologist with the Scripps Institution of Oceanography, explained the current situation could tip either way. The Antarctic ice sheet could add about 55 meters to sea level, and we wouldn’t even know how it happened.

Antarctica’s massive ice shelves are melting at a faster rate than ever. /
PHOTO BY MARIO TAMA

The priority is to find the most resourceful methods of mapping the topography of the sea floor below the melting ice shelves. Right now, scientists don’t even know how thick the ice is, but the task of mapping it is monumental. The huge continent is hard to understand, but the teams of researchers heading out there are doing the best they can with the instruments they have.

Header Image: Ice floats off the coast of West Antarctica. Picture captured on October 27, 2016, from a window of a NASA Operation IceBridge airplane.

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William E. Eubanks
 

I'm one of the main writers on the site; mostly dealing with environmental news and ways to live green. My goal is to educate others about this great planet, and the ways we can help to protect it.

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