Why Antarctic Sea Ice Isn't Shrinking
Winds, currents and seafloor features may be responsible for keeping Antarctica's sea ice intact.
Even as the extent and thickness of sea ice in the Arctic plunges to ever-lower levels, the seasonal sea ice that encircles the frozen continent of Antarctica has stubbornly refused to follow suit. In fact, if anything, the trend is slightly in the other direction. The years 2012 to 2014 saw record highs in Antarctic wintertime sea ice extent, before a return to average levels in 2015. This is despite the fact that water temperatures in the Southern Ocean have been increasing.
Scientists have puzzled over the reason for this; among the theories that have been advanced are that the ozone hole above Antarctica may be resulting in strengthened winds conducive to sea ice formation, or that melting glaciers and ice shelves on the continent are causing a freshening of the sea surface, and thus a higher freezing point (as saltwater freezes at a lower temperature than freshwater).
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A new study may have solved the mystery of Antarctica's resilient sea ice. Its authors argue that two persistent geological factors - the topography of Antarctica and the depth of the ocean surrounding it - are influencing winds and ocean currents, respectively, to drive the formation and evolution of Antarctica's sea ice cover and help sustain it.
Unlike in the Arctic, Antarctic sea ice cover almost completely disappears during summer - its extent in February was, on average, approximately 17 percent of its September peak - and rebuilds anew each fall and winter. By analyzing radar data from NASA's QuikScat satellite to trace the paths of Antarctic sea ice movements and map its different types, Son Nghiem of NASA's Jet Propulsion Laboratory and colleagues found that, early in the growth season, sea ice is pushed offshore by winds, forming a protective shield of older, thicker ice that circulates around the continent.
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These persistent winds, which flow off the continent and are shaped by Antarctica's topography, pile ice up against the ice shield, enhancing its thickness, and create areas of open water nearer to the continent where new ice can form - "ice factories" - in the authors' parlance.
They found that the northern boundary of this "great shield" of ice remains behind a 30-degree F temperature line surrounding Antarctica, which corresponds with the southern front of a boundary between cold and warm waters called the Antarctic Circumpolar Current.
They further found that the path of this current follows the underwater bathymetry: Areas where the seafloor boasts prominent features such as ridges closely align with the path of the current and the shield of ice, but off the coast of West Antarctica, the current spreads out over the deep, smooth seafloor and the extent of sea ice varies considerably from year to year.
The behavior of Antarctic sea ice, the authors concluded, is therefore "not a paradox, as some have suggested" at all. "Our study provides strong evidence that the behavior of Antarctic sea ice is entirely consistent with the geophysical characteristics found in the southern polar region, which differ sharply from those present in the Arctic," said Nghiem.
Older, rougher and thicker Antarctic sea ice appears in the Bellingshausen Sea in Oct. 2007, within the sea ice shield surrounding Antarctica. Some ice in this region is approximately 33 feet (10 meters) thick.
Step right up, folks, and witness Antarctica, the amazing shrinking continent. This polar desert may be the coldest, windiest continent on the planet, but Antarctica has everything the modern adventurer would want, from exotic wildlife to awe-inspiring landscapes to advanced research facilities and more. No amount of showmanship can express the value of the continent of Antarctica more than glimpses of what the polar landscape has to offer the curious traveler. But Antarctica is also under threat like never before in human history. So now is the time to explore the planet's coldest continent before it's too late.
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One of the first stops on any visit to Antarctica should be to see the animals who have basically become a sort of mascot for the continent, the always dapper penguins. While the majestic emperor penguin may be the most famous species in the southern continent, they aren't the only penguins in Antarctica or even the most populous. The Antarctic Circle also hosts four other varieties of penguins, including Adélie penguins, chinstrap penguins, gentoo penguins and macaroni penguins. These birds total in the tens of millions when all the species are combined, but their ranks have been thinned right along with the ice as climate change takes its toll. The shrinking continent threatens both their breeding grounds and food supply, particularly for emperor, Adélie and chinstrap penguins, studies have found.
Penguins aren't the only animals that call Antarctica home. Fish, albatross, seals and other animals share the landscape and can be seen on a typical Antarctic voyage. One of the most easily spotted animals are the whales that swim in the Antarctic Ocean. Many species can be found around the southern continent, including blue whales, killer whales, humpbacks, sperm whales and more. In fact, earlier this year, researchers reported
the discovery of a new whale species
after detecting its unique song pattern. As with penguins, climate change has had an impact on whales for the worse, affecting their migration patterns and food supply.
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Although not as famous as its northern cousin, aurora australis, the Southern Lights, bathe the Antarctic skies in an brilliant green glow. The light show can be credited to solar particles entering Earth's atmosphere. The Southern Lights (pictured over the National Science Foundation's South Pole Station) are less accessible than the Northern Lights, which can be seen over many populated areas. In the south, however, there is little land over which the aurora is viewable. The Southern Lights are also only viewable between March and September, when the days are dark most or all of the time depending on the month. Cruises only travel to Antarctica during the summer months, however, between November and March.
More than 100 years ago, Capt. Robert Falcon Scott led the ill-fated British Antarctic, also known as Terra Nova, expedition. The mission cost him his life but cemented his legacy as a hero. Built in 1911 by crew members of Scott's expedition, the Terra Nova hut is located on Cape Evans on the west side of Ross Island. Measuring 50 feet long (15 meters) by 25 (7.6 meters) wide, the hut was constructed as a base from which Scott would set upon the expedition to the South Pole and could house up to 33 men. More than 8,000 artifacts are preserved in the hut, including furniture, various food items, scientific instruments, photographs and a darkroom.
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Scott's hut isn't the only historic home on the Antarctic site-seeing tour. Ernest Shackleton's hut at Cape Royds, which also conveniently is adjacent to a colony of Adélie penguins, still stands more than 100 years after it was built. Constructed during Shackleton's second expedition to Antarctica between 1907 and 1909, in addition to the various artifacts one might expect an early 20th-century polar explorer to have handy, the historic site also held a cache of 25 cases of whiskey, 12 cases of brandy and six of port.
According to the U.S. Antarctic Program
, the explorers relied on strong spirits to cope with the long insomnia-inducing days and bone-chilling nights.
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Located at the southern tip of Ross Island, McMurdo Station has been the primary Antarctic research facility for the United States since its completion in 1956. The site hosts all the facilities needed for a remote research community, including but not limited to dormitories, administrative buildings, a fire station, a power plant, a water treatment plant, stores, clubs, warehouses, a science support center, a harbor, landing strips, a runway and a helicopter pad. McMurdo supports research programs stretching over a variety of disciplines including astrophysics, glaciology, integrated system science, ocean and atmospheric sciences, according to the U.S. Antarctic program,
which also hosts a live view of the research station online
.
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Don't let the name fool you. Deception Island harbors an honest-to-goodness tourist attraction. In addition to the natural beauty of the area, the site offers a natural hot spring in which travelers can take a soak. For visitors looking to take a trip through time, the island also houses the rusting remnants of a former whale oil outpost, abandoned in the early 1930s when whale oil prices plummeted, as well as is a few buildings that made up a British base, left desolate in the 1970s. Above, an American researcher warms his hands on a seaside fumarole in this photo taken in 1962. Why does Deception Island seem to welcome visitors but discourage settlement? The island is the site of an active volcano, which explains why the only people willing to attempt an extended stay these days are scientists.
When not blocked by icebergs, rendering it impassable, Lemaire Channel offers visitors a postcard-perfect view of Antarctica. Lemaire Channel is roughly 7 miles (11 kilometers) long and runs between Booth Island and the Antarctic peninsula. Ships traveling the channel will be greeted by snow-capped mountains on both sides. The channel also happens to be a prime spot for whale-watching, with humpbacks or killer whales occasionally following a ship's wake.
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No trip to Antarctica would be complete without a visit to the South Pole. Fortunately for the modern traveler, there's no need to travel by foot to get there. The most common means of seeing the South Pole is in a helicopter. In addition to the Amundsen–Scott South Pole Station seen in the Southern Lights slide, the South Pole also carries all of the flags of the nations that lay claim to some slice of Antarctica. The site also contains the Ceremonial South Pole, a metallic sphere on top of a red and white striped pole. Above, the American flag is repositioned every year on New Year's Day to account for the movement of ice.
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