Using ice-penetrating radar and ice cores, NASA has been able to map the layers in the Greenland ice sheet.
This new map allows scientists to determine the age of large swaths of Greenland's ice, extending ice core data for a better picture of the ice sheet's history. "This new, huge data volume records how the ice sheet evolved and how it's flowing today," said Joe MacGregor, a glaciologist at The University of Texas at Austin's Institute for Geophysics and the study's lead author.
Greenland's ice sheet is the second largest mass of ice on Earth, containing enough water to raise ocean levels by about 20 feet. The ice sheet has been losing mass over the past two decades and warming temperatures will mean more losses for Greenland. Scientists are studying ice from different climate periods in the past to better understand how the ice sheet might respond in the future.
One way of studying this distant past is with ice cores. These cylinders of ice drilled from the ice sheet hold evidence of past snow accumulation and temperature and contain impurities like dust and volcanic ash that were carried by snow that accumulated and compacted over hundreds of thousands of years. These layers are visible in ice cores and can be detected with ice-penetrating radar.
Ice-penetrating radar works by sending radar signals into the ice and recording the strength and return time of reflected signals. From those signals, scientists can detect the ice surface, sub-ice bedrock and layers within the ice.
New techniques used in this study allowed scientists to efficiently pick out these layers in radar data. Prior studies had mapped internal layers, but not at the scale made possible by these newer, faster methods. Another major factor in this study was the amount of Greenland IceBridge has measured.
It's amazing that the detectors and data analysis are sensitive enough to pick out different layers in the ice just from radar. (via @ptak)
Greenland has been covered in dark ice this summer. Why is that such a problem? Because dark things absorb more heat than lighter colored things, causing the dark ice to melt faster than white ice would. Eric Hotlhaus explains.
There are several potential explanations for what's going on here. The most likely is that some combination of increasingly infrequent summer snowstorms, wind-blown dust, microbial activity, and forest fire soot led to this year's exceptionally dark ice. A more ominous possibility is that what we're seeing is the start of a cascading feedback loop tied to global warming. Box mentions this summer's mysterious Siberian holes and offshore methane bubbles as evidence that the Arctic can quickly change in unpredictable ways.
This year, Greenland's ice sheet was the darkest Box (or anyone else) has ever measured. Box gives the stunning stats: "In 2014 the ice sheet is precisely 5.6 percent darker, producing an additional absorption of energy equivalent with roughly twice the US annual electricity consumption."
Perhaps coincidentally, 2014 will also be the year with the highest number of forest fires ever measured in Arctic.
Nathan Myhrvold, billionaire polymath, recently wrote a series of three posts for the Freakonomics blog about his trips to Iceland and Greenland.
I'd like to say that global warming was evident during my visit, but that is not really the case. Indeed, [my guide] Salik tells me that he and most Greenlanders are pretty skeptical about it. The local fishing industry used to be based on arctic prawns, but the sea temperature has changed just enough that the prawns are much further north, so now they fish for cod.
But, as Salik points out, this cycle has happened several times in living memory. The same with the glaciers: yes they are retreating, but at least in his area, they have yet to reach the limits that the locals remember them. Objective measurements do show that climate change is happening. Nevertheless I was amused that the locals don't seem to think it is such a big deal.
The photos are worth a look by themselves.
People who live in Greenland are loving this global warming thing. "At a science station in the ice-covered interior of Greenland, average winter temperatures rose nearly 11 degrees Fahrenheit from 1991 to 2003. Winters are shorter, ice is melting, and fish and animals are on the move." 11 degrees in 12 years!