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Iceberg off Mertz Glacier ‘disrupt ocean currents’?

Posted by feww on February 26, 2010

A large iceberg which calved from The Mertz Glacier Tongue in January [see Addendum] could ‘disrupt the ocean currents,’ and weather patterns globally, sensationalist scientists say.

The Mertz Glacier Tongue, which protrudes from East Antarctica, spawned the iceberg pictured below on or about January 10, 2010. The Iceberg is currently floating south of Melbourne, Australia.

The Mertz Glacier routinely spawns icebergs into the Southern Ocean, some of which drift north and disintegrate rapidly in warmer surroundings, while others circle the frozen continent and could stay relatively intact for many years, provided that they remain in cold waters.

Australian scientists have warned, however, that the 80-square-km iceberg (30 sq miles) could block a region which allegedly produces 25 percent of the world’s cold and dense seawater, BBC reported.


On January 10, 2010, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this true-color image of an iceberg that had broken off the glacier tongue. Similar to the glacier that spawned it, this iceberg sports a rippled surface, accentuated by the Sun’s relatively low elevation in the sky when the image was collected. Measuring roughly 8.5 by 9.5 kilometers (5 by 6 miles), this iceberg is surrounded by smaller chunks of ice, which may have broken off the Mertz Glacier Tongue at the same time as the large iceberg, or after it calved.  NASA Earth Observatory image by Jesse Allen, Caption by Michon Scott. Edited by FEWW. Click here for ESA image of the entire
glacier tongue.

A glaciologist at the Antarctic Climate and Ecosystems Research Center in Tasmania, was quoted by the BBC as saying that any disruption to the production of the super cold water – known as bottom water – in the region would be detrimental to ocean currents, and therefore the weather patterns, for many years.

“This area accounts for about 25% of the production of bottom water in Antarctica, and therefore it will reduce the overturning circulation rate,” he said.

“You won’t see it immediately, but it has downstream effects. And it will also have implications for penguins and other wildlife in the region that normally use this area for feeding.”

The iceberg is floating in a polynya, an area of open water surrounded by sea-ice.  Latent heat polynyas are responsible for high ice production and possibly dense (high salinity) water production.

“Bottom water produced by polynyas sinks to the bottom of the sea and drives the conveyor-belt like ocean circulation around the globe.” BBC claimed.

“The ice tongue was almost broken already. It was hanging like a loose tooth,”  BBC quoted a French glaciologist as saying.

“If they [the icebergs] stay in this area – which is likely – they could block the production of this dense water, essentially putting a lid on the polynya.”


This map shows the pattern of thermohaline circulation also known as “meridional overturning circulation”. This collection of currents is responsible for the large-scale exchange of water masses in the ocean, including providing oxygen to the deep ocean. The entire circulation pattern takes  about 2000 years. Credit NASA.

Climate Change is bad news of epic proportions, of course,  and the accelerating rate of calving of icebergs is very alarming, indeed. However, despite its deep injuries, planet earth and its thermoline circulation system are far more resilient than to undergo dramatic changes due to a single iceberg.

ADDENDUM [12:40 PM UTC]

Since posting the above, Fire-Earth moderators have been advised that the iceberg featured above is NOT the one which is the subject of the Antarctic Climate and Ecosystems Cooperative Research Center.

The new iceberg apparently calved off from Mertz Glacier Tongue on or about February 13, 2010.


ESA © ENVISAT ASAR image from the 16th of February 2010 showing the iceberg newly calved from the Mertz Glacier Tongue. The final separation did not simply occur along all the line of the two pre-existing rifts but sheared across some sections to produce a clean line. The iceberg is now turning about a point at its north-west corner which confirms our belief that is has been resting against a relatively shallow point of the sea-floor. Caption: ACECRC.

According to the ACECRC website the iceberg that calved from the Mertz Glacier is 78 km long and has a surface area of 2,500 square km. The new iceberg broke off the Mertz Glacier Tongue after a 97km long iceberg smashed into it.

Although the new iceberg is about 30 times larger than the one featured in NASA image (Top of the page), the Fire-Earth Moderators’ initial assessment remains UNCHANGED.

The Moderators do NOT believe the new calving would ADVERSELY affect the large scale ocean circulation, or have any significant climatic impact.

Further more, they see absolutely NO reason why the iceberg may cause significant modifications in the local marine environment.

Additional Notes:

The BBC Himalayan Straw Man?

The Moderators also note that the BBC has since changed the text of the page linked to above  http://news.bbc.co.uk/2/hi/science/nature/8538060.stm

However, the page was accidentally saved on disk …


BBC’s initial post, which has since been replaced by an entirely different text. Click image to enlarge. Image may be subject to copyright.


BBC’s 2nd version using the same URL was a pathetic dolphin tearjerker, which has since been removed.
Click image to enlarge. Image may be subject to copyright.

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