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Alaska’s Freshwater Is Draining Into the Sea at an Astounding Rate

Satellite data shows that snow and glacial melt are partially to blame for an annual freshwater output 1.5 times that of Mississippi River

Meltwater from the Brady Glacier (shown in the foreground) is seen in Glacier Bay National Park and Preserve. The water in the foreground in the southwest (bottom left) corner of the image is the Gulf of Alaska. (NASA/Corbis)
smithsonian.com

Forty percent of the continental United States, as well as two Canadian provinces, are drained by the mighty Mississippi River. All of that water is dumped into the Gulf of Mexico at a rate of 600,000 cubic feet per second. For comparison, that’s about 9,960 semi-truck trailers full of fresh water being spit into the ocean every single minute.

That’s a whole lot of liquid. But, as a new study confirms and i09 recently reported, that's actually much less than amount of freshwater that Alaska is expelling every year. Due in part to glacial melt, the northern state annually dumps 1.5 times the amount of fresh water that the Mississippi does.

For the study, data gathered over the last three decades was combined with new gravity measurements gleaned from two NASA satellites. Together, the information helped geophysicists calculate the amount of water draining from the state and from where it originated. 

As Ned Rozell at Alaska Dispatch News reports, half of this output comes from rainfall in Alaska’s wet south and southeast regions. The other half, however, originates from rapidly melting snow, glaciers and ice fields.

The movement of such a large volume of glacial meltwater has some wide-reaching ecological consequences, as Rozell lays out:

Fresh water helps power ocean currents that carry heat to cooler places. Glaciers gather bits and pieces of life that, once transported by meltwater, feed tiny things in the ocean, which feed salmon and other creatures. Glacial rivers move the stuff of life, carbon, and redeposit it to the sea. Glacial melt increases sea level. And Alaska and northern Canada are moving water like a fire hose that grows in diameter each summer.

Yet, though the volume of water expelled by Alaska is likely to go up as glaciers continue to melt, the state’s heavy annual snowfall means that much of that liquid will return to the land. And so Alaska’s drainage only accounts for a 2 percent rise in sea level. Greenland, on the other hand, accounts for a whopping 20 percent of current sea level rise, because its fresh water loss is due primarily to mostly non-returnable glacial melt.

Studies have shown that increasing amounts of fresh water in the ocean likely contributes to bigger or more frequent storms in some areas and droughts in others. Though it will take time to quantify, one of the study’s main authors, glaciologist Anthony Arendt, predicts that the overall impact of Alaska’s huge fresh water output will likely be complex and continuous—which is in keeping with other large-scale effects of climate change.

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