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Holiday calendar: Santa's shrinking domain

Few places on Earth have more of a connection to the holiday season than the North Pole: After all, that's where Santa Claus hangs his hat. That's the address most kids write on their Christmas letters. Even NORAD lists that locale as Santa's home base.

But if I were Santa, I'd start thinking about real estate: Over the years, satellite measurements have pointed to a shrinkage in ice extent and thickness in the Arctic, due to rising temperatures. In September, experts at the National Snow and Ice Data Center reported that Arctic sea ice had declined to its second-lowest level in the past 32 years, and researchers at the University of Bremen in Germany said the ice coverage had fallen even below the 2007 minimum. This report from the European Space Agency helps put the issue in perspective.

With the approach of northern winter, the ice is returning. The picture above, based on data from NASA's Aqua satellite, shows the maximum and minimum extent of Arctic ice this year. ESA has an animation that illustrates the annual fluctuation in a moving way. Santa shouldn't have to worry about shrinking sea ice between now and Christmas. But once the holiday rush is over, he might want to keep an eye on msnbc.com's Environment coverage. There may well be a "new normal" in the Arctic from now on.

Today's Arctic offering is part of the Cosmic Log Space Advent Calendar, which provides a daily view of Earth from space from now until Christmas. Check out these previous entries on the calendar, as well as other space-themed Advent calendars online. And check in again on Sunday for the next visual treat.

Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.