Wednesday, August 21, 2019

Greenland's melt signals 'the end of the planet' as we know it

AP Science Writer Seth Borenstein explains how Earth’s future is being written in fast-melting Greenland in this morning’s Daily Star. Here are excerpts.

HELHEIM GLACIER, Greenland (AP) — This is where Earth’s refrigerator door is left open, where glaciers dwindle and seas begin to rise.

New York University air and ocean scientist David Holland, who is tracking what’s happening in Greenland from both above and below, calls it “the end of the planet.” He is referring to geography more than the future. Yet in many ways this place is where the planet’s warmer and watery future is being written.

The ice Holland is standing on is thousands of years old. It will be gone within a year or two, adding yet more water to rising seas worldwide.

Summer this year is hitting Greenland hard with record-shattering heat and extreme melt. By the end of the summer, about 440 billion tons (400 billion metric tons) of ice — maybe more — will have melted or calved off Greenland’s giant ice sheet, scientists estimate. That’s enough water to flood Pennsylvania or the country of Greece about a foot (35 centimeters) deep.

A NASA satellite found that Greenland’s ice sheet lost about 255 billion metric tons of ice a year between 2003 and 2016, with the loss rate generally getting worse over that period. Nearly all of the 28 Greenland glaciers that Danish climate scientist Ruth Mottram measured are retreating, especially Helheim.

Let’s take a computational pause. 2003 to 2016 is 14 years. 14 x 255 = 3,570 billion metric tons. Divide that by 400 billion metric tons (flooding Pennsylvania) and we get 8.925 states the size of Pennsylvania (or 8.925 countries the size of Greece). I offer the computation to give you an idea of the magnitudes of the melt we are facing. There’s lots more that would need to be computed to figure out the sea level rise should the entire Greenland ice sheet melt.

Several scientists, such as NASA oceanographer Josh Willis, who is also in Greenland, studying melting ice from above, said what’s happening is a combination of man-made climate change and natural but weird weather patterns. Glaciers here do shrink in the summer and grow in the winter, but nothing like this year.

Holland and team climb out to install radar and GPS to track the ice movement and help explain why salty, warm, once-tropical water attacking the glacier’s “underbelly” has been bubbling to the surface

“It takes a really long time to grow an ice sheet, thousands and thousands of years, but they can be broken up or destroyed quite rapidly,” Holland said.

Holland, like NASA’s Willis, suspects that warm, salty water that comes in part from the Gulf Stream in North America is playing a bigger role than previously thought in melting Greenland’s ice. And if that’s the case, that’s probably bad news for the planet, because it means faster and more melting and higher sea level rise. Willis said that by the year 2100, Greenland alone could cause 3 or 4 feet (more than 1 meter) of sea level rise.

In this remote landscape, sound travels easily for miles. Every several minutes there’s a faint rumbling that sounds like thunder, but it’s not. It’s ice cracking.

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