Giant Icebergs Break Free, Threaten Ocean Currents and Oxygen Levels


A giant iceberg in the southern Atlantic. Image credit: Wikimedia Commons

On February 12 or 13, a truly mammoth iceberg broke free from the Mertz Glacier Tongue. The 985 square-mile block of ice is roughly the size of Luxembourg and, at 1300 feet thick, would fill Sydney Harbor more than 100 times. The block was dislodged by another large iceberg—known as B9B—which cleaved in 1987.

Now drifting together in the Southern Ocean, the icebergs are threatening—researchers report—to cap an important region responsible for driving the world's ocean currents.

The Importance of Polynyas

A polynya is an area of unfrozen water surrounded at least in part by sea ice. These areas generate very cold, dense, water with a high salt content. This water eventually sinks—a process that fuels the circulation of global ocean currents.

Slideshow: David Burdeny's Incredible Iceberg Photography

When floating sea ice, like giant icebergs, covers the surface water of the polynya this process stops, resulting in an overall slowdown of ocean currents. These currents, of course, play a huge role in regulating global weather patterns, and are also responsible for distributing oxygen throughout the oceans.

Threatened by Icebergs

Of course, the icebergs will eventually melt, but if they remain in the Southern Ocean, which is expected, it could take decades for this to happen. In the meantime, they would block this important circulation process.

Researchers pointed out that polynyas are relatively uncommon and that the Metz Glacier Polynya is particularly strong—providing 20 percent of the world's "bottom water."

Mario Hoppema, a chemical oceanographer at the Alfred Wegener Institute for Polar and Marine Research, explained:

There may be regions of the world's oceans that lose oxygen, and then of course most of the life there will die.

Researchers said that it was difficult to attribute this event directly to melting from climate change, but Glaciologist Benoit Legresy pointed out that, "obviously when there is warmer water, these ice tongues will become more fragile."

Read more about Antarctic melting:
David Burdeny's Incredible Iceberg Photography (Slideshow)
Antarctica's Pine Island Glacier Melting Four Times Faster Than 10 Years Ago
West Antarctic Glacier Disintegrating Rapidly: First Hand Account
Ice Loss in Antarctic Peninsula Unprecedented in 14,000 Years

Tags: Global Warming Effects | Oceans

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