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The world's mountain glaciers contain just 1% of all the ice on Earth, but their rapid melting accounts for about a third of recent sea level rise. This is Scientific American's 60 Seconds Science. I'm Julia ?Rosen?. Got a minute? Most of these glaciers that start ?and? end on land shrink away through gradual surface melting, but others known as tide-water glaciers flow out into the sea and by calving off mass of icebergs these glaciers can collapse in the blink of an eye, geologically speaking. For example, the Columbia Glacier in Alaska's ?Chugetch? mountains is a tide-water glacier that once filled a long fjord. It's retreated 12 miles in just the last 25 years. So this tiny little glacier in Alaska is capable of producing 1% of ?the? sea level rise budget. And so we know that individual calving glaciers can do crazy things and can act really dramatically and can have this rapid response. Shad O'Neel, a glaciologist with the US Geological Survey in Anchorage and co-author of a new study in The Journal Geophysical Research Letters. Scientists thought that tide-water glaciers, because of their unstable behavior, might be an important source of the torrent of meltwater flowing out of Alaska and northwest Canada, where ice has been disappearing at especially alarming rates. But all mountain glaciers, tide-water and otherwise, are notoriously hard to quantify, so O'Neel and his colleagues undertook the daunting task of assessing the health of every glacier in the region. Using data collected from airplanes, they tracked ??? masses of a hundred and sixteen glaciers making up 41% of Alaska's ice-covered area changed through decades. Then they used similarities in the shape, size and location of the remaining 27,000 glaciers to estimate how those changed too. The results surprised them. tide-water glaciers accounted for just 6% of the region's total ice loss. The vast majority came from surface melting of glaciers that ?are? completely on land. So ?you are?, your initial response is 'Wow, this is great! The tide-water glaciers actually aren't doing that much in Alaska.' That sounds like good news because tide-water glaciers can shed a lot of ice really quickly. But scientists expect the sea level contribution of tide-water glaciers to wind down in the near future as they retreat up fjords and onto land. But the surface melt part is not going to decrease, which we now know drives most of the region's ice loss. It means that while we might have more certainty about what's happening, we also, that means that we have more certainty that Alaska's contribution is gonna stay the same or grow as climate continues to warm. Thanks for the minute. For Scientific American's 60 Seconds Science. I'm Julia ?Rosen?.
