A pair of studies were released yesterday and they suggest existing computer models showing Greenland’s ice melt are wrong.
The scientists say if all of the ice was to melt in Greenland, the world’s oceans would rise by 20 feet. So much for that beach side property. But, when could that happen? Not in our lifetimes. But, that doesn’t mean we won’t see some rise in sea levels during our lifetime.
Greenland’s ice loss is expected to add 8 inches to global sea levels by 2100. But, these new studies suggest that figure is extremely conservative.
One of the studies shows that as temperatures continue to rise, ‘supraglacial’ lakes will become more numerous. These lakes sit atop the ice and speed up the melting process.
Since the lakes are darker than the white ice, they absorb more of the sun’s heating. These lakes also create channels in the ice sheet, which weakens it further.
Study lead author Amber Leeson compares the lakes effect on ice to pancakes.
“When you pour pancake batter into a pan, if it rushes quickly to the edges of the pan, you end up with a thin pancake,” study lead author Amber Leeson said explained in a statement. “It’s similar to what happens with ice sheets: The faster it flows, the thinner it will be.”
“When the ice sheet is thinner,” she added, “it is at a slightly lower elevation and at the mercy of warmer air temperatures than it would have been if it were thicker, increasing the size of the melt zone around the edge of the ice sheet.”
The image below shows what the supraglacial lakes look like. They are the dark blue dots.
Right now, the lakes are limited to low-lying areas around Greenland’s coastline. It hasn’t been cold enough in inland areas for the lakes to form. This study suggests warmer temperatures will lead to an increase in lakes. By 2060, the lakes will cover an area double the size of today.
A second study also indicated current models are “too simplistic.” The study, led by Beata Csatho, an associate professor of Geology at the University of Buffalo, used satellite and aerial data to measure 100,000 locations.
The researchers wanted to see how the height of Greenland’s ice sheet changed from 1993 to 2012.
Before I dive into their findings, let’s look at how models forecast Greenland’s ice melt. Just four glaciers are used in today’s models – Jakobshavn, Helheim, Kangerlussuaq and Petermann.
Csatho’s findings suggest these four glaciers don’t provide the whole story on Greenland’s ice sheet.
“There are 242 outlet glaciers wider than 1.5 km on the Greenland Ice Sheet, and what we see is that their behavior is complex in space and time,” Csatho says. “The local climate and geological conditions, the local hydrology — all of these factors have an effect. The current models do not address this complexity.”
So, how much ice is Greenland losing?
Between 2003-2009, the Greenland ice sheet lost 243 metric gigatons of ice every year. That equals about 0.68 millimeters of water added to the oceans every single year.
Global warming’s impact on Greenland’s glaciers is difficult to predict. Csatho and her team found some glaciers actually thickened as temperatures rose. Others saw fast thinking. Some had a bit of both.
To help create better models, the scientists took the 242 glaciers they studied and split them into 7 groups based on their behavior during the 2003-2009 timeframe.
“Understanding the groupings will help us pick out examples of glaciers that are representative of the whole,” Csatho says. “We can then use data from these representative glaciers in models to provide a more complete picture of what is happening.”
Image credits: Beata Csatho, NASA