Science news has been buzzing lately about imagery from three satellites showing indications of melting snow and ice on Greenland. As we all learn in science classes, Greenland is basically a very large sheet of ice, so to see such melting as this is quite striking. Definitely newsworthy.
The image on the left is from 8 July 12, while that on the right is from 12 July 2012, showing a profound increase in reflectivity of the landmass. Photo: WIRED
I was certainly interested in learning more. My master’s thesis 10 years ago was in remote sensing meteorology, meaning I was taking a measurement of one item and applying algorithms to translate it into another data point. In my case I was working with GPS error data that was converted into a surrogate measurement of water vapor in the atmosphere; that data could be used to estimate humidity.
In the case of this recent news, satellites are using the microwave portion of the electromagnetic spectrum to measure reflectivity of the earth’s surface and applying algorithms to translate it into melted ice. It’s pretty accurate, no argument there.
From 8 July to 12 July, Greenland’s surface transitioned from approximately 40% melted water to approximately 97%. That’s a lot of melting in not a lot of time. The first indications were seen while analyzing radar reflectivity data from the Indian Space Research Organisation’s (ISRO) Oceansat-2 satellite, then it was verified with temperature data from the American Moderate-resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra and Aqua satellites. Scientists at NASA Goddard Space Flight Center verified that the MODIS data indicated unusually high temperatures during the second week of July over the landmass; these conditions coincided with an upper air high pressure system, the same large-scale phenomena that has caused the recent heat waves in the eastern United States.
A third satellite verification was brought in, thanks to analyses from the Special Sensor Microwave Imager (SSM/I) on the U.S. Air Force’s Defense Meteorological Satellite Program (DMSP) satellites. Several of the channels on the SSM/I imager are tuned to sense data through the atmosphere all the way to the surface of the earth, detecting whether the surface is dry, flooded, forested, ocean water, iced-over or thawed.
Finally, on-site weather observations at research stations throughout Greenland have verified the warmer temperatures that correlate with the surface ice melting.
While this news is very significant in the climatology and glaciology community, some are going step further and are attempting to connect it with other indicators of climate change. The definitive answer to that question is not clear and many news outlets are doing a good job providing a balanced view of this news. Several points should be made about this news:
Continue reading at WIRED
