Epic Iceberg Smashup Could Change Currents

Ice Tongue Takes a Licking

Photograph courtesy Neal Young, Commonwealth of Australia

Days before the mid-February collision, iceberg B9B approaches dangerously close to the Mertz Glacier Tongue on February 7 in a satellite picture.

Speaking of the February 12 or 13 smashup, Waleed Abdalati, director of the Earth Science and Observation Center in CIRES at the University of Colorado, said the iceberg collision shouldn't be seen as a symbol of global warming.

"This is a natural process," Abdalati said. "It's a collision of giants in the Southern Hemisphere—but the question becomes, do rising air temperatures and warming sea temperatures make the ice more vulnerable to this type of phenomenon?"

(Pictures: Antarctica Warming.)

March 1, 2010

Giant Icebergs Depart Antarctica

Photograph courtesy Neal Young, Commonwealth of Australia

Now floating free of the Australian Antarctic Territory, both of the giant icebergs move toward the Adélie Depression coastal basin in a February 20 satellite picture.

The basin has been one of the world's more important sites for the formation of supersalty, dense water, which helps drive deep-ocean circulation and in turn influence Earth’s climate, in part by moving heat around the planet.

Dense water forms in the open-water basin when seawater interacts with the glacier tongue, and when winds help form sea ice, releasing salt into the waters below. The appearance of an enormous iceberg in these waters could block these processes, stalling dense water formation and possibly shifting ocean currents—with unknown results.

(Related: "Antarctic Icebergs Teeming With Life, Study Says.")

March 1, 2010

Sliding Toward Icy Surprise?

Photograph by Bill Curtsinger, National Geographic Stock

"When you affect the circulation of the ocean"—as the newly free-floating icebergs may do—"that means you also affect the movement of all the organisms in that area of the ocean," said sea ice expert Claire Parkinson at NASA’s Goddard Space Flight Center.

Parkinson noted that such changes—which can include the out-migration of prey animals—can have unpredictable consequences for the marine ecosystem's entire food chain, including emperor penguins (pictured in a file photo). Marine species here include the emperor penguin colony seen in the movie March of the Penguins.

For example, the northward extension of sea ice into formerly open waters could block sunlight needed by ocean organisms for photosynthesis—with ramifications higher up the food chain, Parkinson said.

And the newly floating ice may simply get in the way. "That is a very large block of ice to all of a sudden be in a path a penguin might be [used to] taking," she said.

(Related: "Hundreds of Glaciers Melting Faster in Antarctica.")

March 1, 2010

Icebergs May Throw Currents for a Loop

Diagram courtesy U.S. Global Change Research Program

The deep, cold current off Antarctica is part of the worldwide ocean "conveyor belt" (pictured), which pulls nutrient-rich waters from the deep ocean, brings them to the surface, and distributes them around the world.

"The future position of the two giant icebergs will likely affect local ocean circulation ... sea ice production, and deep water formation,” ACECRC researchers said in a statement.

The Mertz Glacier is located toward the eastern end of Antarctica, next to the cold and salty deep current. The giant icebergs could alter the cold, deep current by stalling the formation of current-driving dense water.

Because dense water also sinks into the deep sea, delivering oxygen to its denizens, some scientists have even suggested that the recent iceberg event could create oxygen-poor "death zones," in some parts of the ocean.

March 1, 2010