Climate Denial Crock of the Week

In the ebb and flow of climate information, there seems, lately, to be a pulse of new findings relevant to the accelerating melt of ice sheets.

Scientific American:

As happens so often in science, Mike Willis wasn’t actually looking for what he ended up discovering. The glaciologist was combing through satellite and GPS data to see what small, local effects could be clouding satellite measurements of larger changes in Earth’s gravity from ice loss.

What he did not expect to find was a hole twice the size of Central Park in a small ice cap in the northern reaches of Greenland.

“What the heck is that?” he thought when he saw it.

He didn’t think he could possibly be the first person to have spotted it. “Surely someone’s noticed a gigantic hole in northern Greenland before,” he said, but there were no records of it.

Trying to guess what it could be, he and his colleagues ruled out a meteor crater, a volcano, and, as they joked, Dr. Evil’s sub-ice lair. Ultimately, “the thing that fits it best is that it’s a subglacial lake,” he said.

Such lakes of water pool at the bottom of an ice sheet or glacier, and were known to be scattered under parts of Antarctica. But they hadn’t been found yet in Greenland.

Looking through satellite data going back to the 1970s, Willis couldn’t find any sign of the hole until 2006. At that point surface water in the area was flowing in an unexpected direction and disappearing down a moulin right in the spot Willis was looking at. That flow pattern repeated every few years, and then in 2011, “Boom! A big hole appears in the place where the water disappeared,” he said.

Ohio State University:

COLUMBUS, Ohio—Researchers who are building the highest-resolution map of the Greenland Ice Sheet to date have made a surprising discovery: two lakes of meltwater that pooled beneath the ice and rapidly drained away.

One lake once held billions of gallons of water and emptied to form a mile-wide crater in just a few weeks. The other lake has filled and emptied twice in the last two years.

Researchers at The Ohio State University published findings on each lake separately: the first in the open-access journal The Cryosphere,  and the second in the journal Nature.

Ian Howat, associate professor of earth sciences at Ohio State, leads the team that discovered the cratered lake described in The Cryosphere. To him, the find adds to a growing body of evidence that meltwater has started overflowing the ice sheet’s natural plumbing system and is causing “blowouts” that simply drain lakes away.

“The fact that our lake appears to have been stable for at least several decades, and then drained in a matter of weeks—or less—after a few very hot summers, may signal a fundamental change happening in the ice sheet,” Howat said.

Guardian:

The planet’s two largest ice sheets – in Greenland and Antarctica – are now being depleted at an astonishing rate of 120 cubic miles each year. That is the discovery made by scientists using data from CryoSat-2, the European probe that has been measuring the thickness of Earth’s ice sheets and glaciers since it was launched by the European Space Agency in 2010.

Even more alarming, the rate of loss of ice from the two regions has more than doubled since 2009, revealing the dramatic impact that climate change is beginning to have on our world.

The researchers, based at Germany’s Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research – used 200m data points across Antarctica and 14.3m across Greenland, all collected by CryoSat, to study how the ice sheets there had changed over the past three years. The satellite carries a high-precision altimeter, which sends out short radar pulses that bounce off the ice surface and then back to the satellite. By measuring the time this takes, the height of the ice beneath the spacecraft can be calculated.

It was found from the average drops in elevation that were detected by CryoSat that Greenland alone is losing about 90 cubic miles a year, while in Antarctica the annual volume loss is about 30 cubic miles. These rates of loss – described as “incredible” by one researcher – are the highest observed since altimetry satellite records began about 20 years ago, and they mean that the ice sheets’ annual contribution to sea-level rise has doubled since 2009, say the researchers whose work was published in the journal Cryosphere last week.