Photo Credit: Ken Klassy/Antarctic Photo Library

McMurdo Station entered the long Antarctic winter night in late April. The sun won't return until August. June 21 marks the winter solstice in Antarctica, when wintering crews from around the world pause in celebration that the long months of isolation are half over.

Antarctica’s most revered holiday was celebrated around the continent today. June 21, 2011 (local time), marks the winter solstice, the shortest “day” of the year in the Southern Hemisphere. Midwinter is a cause for celebration among the wintering parties in Antarctica, a tradition that dates back to the hearty explorers of the early 20th century, who would hold grand feasts. Every day after midwinter is another day closer to the return of the sun — reason enough to celebrate for those spending the winter months in the dark and cold of Antarctica.

This winter perhaps holds perhaps a bit more significance than most in Antarctic history. One hundred years ago, British and Norwegian explorers were both wintering over in preparation for their historic race to the South Pole during the succeeding summer. Norwegian Roald Amundsen would eventually win the race, while British Capt. Robert F. Scott and his party would pay the ultimate price for failure.

Today’s research station crews exchange Midwinter Greetings to one another through email, usually with photos of the group and a message of goodwill for the more than 40 permanent research stations on the continent. U.S. President Barack Obama , in a tradition that dates back to the International Geophysical Year , also sent his midwinter greetings from the White House to the “international community wintering in Antarctica,” in part saying:

“The dangers posed by climate change threaten every nation on Earth and will determine what kind of world our children will inherit. To protect our planet, we must better understand the role of the Polar Regions in Earth’s climate system, and how polar ecosystems are responding to variations in climate and greenhouse gases. Researchers working in Antarctica are at the forefront of understanding what these changes will mean for our ecosystems and for future generations.”

Copies of the McMurdo, South Pole and Palmer station greetings can be found here  on the USAP.gov website.