Mertz Glacier calving leads to reduced sea ice

Mertz, a heavily crevassed glacier in George V Land of east Antarctica, has a tongue that protrudes 100km into the Southern Ocean.  In February, 2010 it split in half due to the collision with iceberg B9-B, which had broken off the Ross Ice Shelf in 1987.  The newly formed iceberg was called Iceberg C-28.  (It was the 28th large calving in the region of Antarctica facing Australia.)  Now scientists from the Antarctic Climate & Ecosystems Cooperative Research Centre (ACE CRC) have determined that sea ice production has decreased significantly since the calving.  They used satellite data to determine that there has been a 14-20% reduction, about half of which can be attributed to the the creation of Iceberg C-28.

You may be asking yourself–

Who cares?

And the answer is: anyone who is interested in Antarctic Bottom Water, and that includes me since I have already done a blog post on it Here.  It turns out that sea ice is critical for the formation of ABW. Special regions of sea ice production, also called polynyas or ice factories, form the dense shelf water from the brine left over from when sea ice freezes   The shelf water sinks, because it is heavier, and that is what creates ABW.  And if you read my other blog posting, you will know that ABW is a major driver of global ocean currents and mixing.  It’s disappearing, rapidly, and no one is really sure what sort of effect this might have on climate.

Although calving events are a natural part of ice-sea interaction over time, ACE CRC sea-ice specialist Dr Guy Williams was still pleased to be able to study such an event.  He said:

“Here, for the first time, we are closely observing an important Antarctic polynya environment before and after such an event. In that sense East Antarctic ocean climate history is unfolding before our eyes and it is a very exciting experiment to be involved in.”

The paper, published in Nature Communications, was co-authored by Takeshi Tamura (National Institute of Polar Research, Japan, ACE CRC) and Guy Williams (ACE CRC), with Alex Fraser (ACE CRC) and K.I. Ohshima (Institute of Low Temperature of Science, Japan).

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