Historic Alaskan Glacier Melt Less Than Previously Thought... But Recent Retreat is Double the Average

alaska glacier photo

photo: Frank Kovalchek via flickr.

Here's one with a decided twist: Scientists from France's Laboratory for Space Studies in Geophysics and Oceanography are saying that previous studies of how much melting Alaskan and Canadian glaciers have contributed to sea level rise have overestimated the situation. However, melting since the mid-1990s is still double the historical average:Writing in the journal Nature Geoscience, the researchers determined that a more accurate estimate of how much these glaciers have contributed to sea level rise during the period of 1962-2006 is 0.12mm/year. Previous analysis showed the the rate was 0.17mm/year.

Melting Accelerated Since the Mid-1990s
If there's good news to be had in this, that is it. The less good news is that "thinning (sometimes over 10 meters per year, as in the Columbia glacier) and glacial retreat remain considerable." (Science Daily) Since the mid-1990s mass loss of Alaskan glaciers has accelerated, and since this period they have contribued 0.25-0.30 mm/year to global sea level rise.

New Satellite Data More Accurate Than Older Measurements
The scientists say that previous analysis overestimated ice loss in these glaciers because: 1) some glacier tongues are covered by rock debris which protects them from solar radiation, which was not taken into account; and, 2) previous sampling, taking longitudinal profiles along the center of glaciers (rather than the satellite measuring used here), was simply less accurate due to the fact that thinning of these glaciers is uneven.

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