The elevation is zero. So, it is rather the glacier (rather than the coastline) which expands and draws back according to the seasons.
On the other hand, GE team removes the sea from the images at the moment.
So, there should be an exception for the glaciers, in my opinion. If not, the lo-res and hi-res imageries and even (in the future) the old hi-res and the updated new hi-res imageries can mess up.
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