US Releases Arctic Ice Images

Reuters has a report on the release by the US government of a series of images, taken by intelligence satellites, of Arctic sea ice coverage at six sites around the Arctic Ocean, and some additional sites in the United States.

Some 700 images show swatches of sea ice from six sites around the Arctic Ocean, with an additional 500 images of 22 sites in the United States. The images can be seen online at gfl.usgs.gov/.

The images were released following a recommendation to do so by the National Academy of Science, in order to contribute to the study of climate change.  This is noteworthy for at least two reasons:

  • These images have much higher resolution than the best previously available unclassified data.  The new images have a resolution of about 1 meter, compared to 15-30 meters in the older images.
  • The images were released on the same day as the NAS report, an uncommonly quick response for a government agency.

The higher resolution allows smaller features to be identified that, while not significant individually, may collectively be quite important in understanding and modeling the processes that lead to ice formation and melting.

For example, during the summer months, pools of melted water form on top of Arctic ice floes, and these puddles can stretch across 30 meters. The water in the puddles is dark and absorbs heat, as opposed to the white ice all around them, which reflects heat.

This is actually an instance of a larger problem that affects not only the analysis of climate change, but more prosaic things like weather forecasting.  The physical processes that contribute to the weather, for example, are reasonably well-understood, and can be described, typically, by systems of differential equations.  One of the standard approximation techniques for solviing these equations is the replacement of the differential equations with difference equations on a grid (3-dimensional, in this case).  This method works well when data can be observed and measured across the grid; but in the case of weather, there are many points where the data is missing.

Regardless of one’s view of global warming, the availability of more specific evidence has got to be a good thing.

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