BBC: The ubiquitous shallow icy lakes that dominate Alaska's Arctic coastal plain have undergone a significant change in recent decades.
These lakes, many of which are no more than 3m deep, melt earlier in the season and retain open water conditions for much longer.
And 20 years of satellite radar also now show that far fewer will freeze right through to the bottom in winter.
The results of the space-borne survey are published in The Cryosphere.
What is happening to the lakes is an example...