Another massive iceberg is calved in Antarctica, with implications for local ocean circulation and wildlife

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"Another massive iceberg is calved in Antarctica, with implications for local ocean circulation and wildlife"

Researchers announced last week that a giant iceberg has collided with a seaward extension of East Antarctica’s Mertz Glacier, breaking a huge chunk off of the glacier to form a second iceberg 78 km (48 miles) long, 33 to 39 km (21-24 miles) wide and 400 m (0.25 mile) thick.  A team of Australian and French scientists say that “[t]he future behavior of the two icebergs is of great interest,” with potential impacts on local ocean circulation, and on the region’s marine biology — including emperor penguins. 

Guest blogger Nick Sundt has the story in a piece first published here.  For some background, see Satellite data stunner: “Our data suggest that EAST Antarctica is losing mass”¦. Antarctica may soon be contributing significantly more to global sea-level rise.”

Until earlier this month, the “tongue” of the Mertz Glacier extended 160 km into the Southern Ocean from the glacier’s “grounding line,” the point beyond which the tongue of ice floats on the ocean’s surface.  Since 1992, a large iceberg called B-9B, sat 100 km to the east on the Ninnis Bank where it had run aground.  B-9B was a piece of a larger iceberg called B-9 that had broken off of (or “calved” from) the Ross Ice Shelf in 1987.  See What’s Happening: Another Massive Iceberg is Born [PDF] (2002) for an illustration showing the tracks of these and other icebergs around Antarctica.  See the image below, showing the relationship between the Mertz Glacier tongue and iceberg B-9B at the end of December 2007.

The image below, from the European Space Agency, showing the Mertz Glacier Tongue on the left and the very large Iceberg B-9B to the right on 11 December 2007.

After about 18 years in the same place, iceberg B-9B — now 97 km by 20-35 km — floated free and rotated into the Mertz Glacier tongue.  The iceberg collided with the Mertz Glacier tongue around 7 February, and by 12/13 February a large piece of the tongue broke off at a point where existing rifts on the glacier tongue created a weak spot. By 20 February, the newly calved iceberg from the Mertz Glacier was drifting free from the glacier.  The three images below document the changes from 7 January through 20 February.

B9B approaches the Mertz Glacier tongue 7 January 2010.  Photo: Neal Young
Above: B9B approaches the Mertz Glacier tongue 7 January 2010. Photo: Neal Young

B9B makes contact 7 February 2010.  Photo: Neal Young
Above: B9B makes contact 7 February 2010. Photo: Neal Young

The Mertz Glacier tongue breaks off 20 February 2010.  Photo: Neal Young
Above: The Mertz Glacier tongue breaks off 20 February 2010. Photo: Neal Young

The Mertz Glacier tongue now extends only 80 km from the glacier’s grounding line, i.e. the length beyond the grounding line has been cut in half.

The dramatic change in the Mertz Glacier tongue, and the movement of the two massive icebergs is particularly important because of the Mertz Glacier Polynya that forms each Winter to the West of the glacier tongue.  According to the Antarctic Climate & Ecosystems Cooperative Research Centre (ACE CRC) (Antarctic polynyas: Nature’s sea ice factories):

“A polynya is a large body of open water or an area covered by very thin ice that persists in the middle of winter sea ice in the polar regions… Although relatively small in area, coastal polynyas play a disproportionately important role in many important physical and biological processes in the high-latitude Southern Ocean, as well as having an impact on global ocean circulation.

ACE CRC says, for example that “the Mertz Glacier Polynya … covers only 0.001% of the overall Antarctic sea ice zone at its maximum winter extent, but is responsible for 1% of the total sea ice production in the Southern Ocean.”

The collision of the B-9B glacier into the Mertz Glacier tongue was detected and initially reported by a joint French-Australian team working on a project called “CRACICE” (Cooperative Research into Antarctic Calving and Iceberg Evolution).  According to a press release [PDF] issued by the team, the volume of ice in the new iceberg “represents about 70 years of glacier advance.”

The press release [PDF] said:

The future behavior of the two icebergs is of great interest. Satellite images show that the recently-calved Mertz iceberg is moving into the Ad©lie Depression, a coastal basin situated between the Mertz Glacier and the French Antarctic station of Dumont D’Urville to the west. This depression one of the major sites of dense water formation which drives the world’s deep ocean circulation. The dense water is formed from ocean water that circulates onto the continental shelf and interacts with the glacier tongue, and by high rates of sea ice formation within the Mertz Glacier polynya to the immediate west of the former glacier tongue. The future position of the two giant icebergs will likely affect local ocean circulation, the extent (and timing?) of the polynya, sea ice production, and deep water formation...This calving is indeed a unique in-situ sensitivity experiment that will help to evaluate the climatic impacts of this region on the large scale ocean circulation.” [emphasis added]

The scientists also report that the event has “important implications for the marine biology of this region.” It says that the region’s polynyas

“constitute places of high biodiversity and food concentration for birds and marine mammals, in particular emperor penguins the only birds to reproduce during winter in Antarctica. The emperor colony at Pointe G©ologie, next to Dumont d’Urville, is closely dependent on the ocean resources. Therefore significant modifications in the marine environment may have large consequences, not only on the local biodiversity but also on this emblematic penguin colony that was brought to prominence in the movie by Luc Jacquet March of the Penguins…” [emphasis added]

Aptenodytes forsteri Emperor penguin Adults and chicks Dawson-Lambton Glacier, Antarctica.  Source: Fritz Polking / WWF.
Above: Aptenodytes forsteri Emperor penguin Adults and chicks Dawson-Lambton Glacier, Antarctica.  Source: Fritz Polking / WWF.

We reported in January that Antarctica is losing more than 24 cubic miles of ice annually — and the pace is accelerating.  Last year was the warmest on record for the Southern Hemisphere, and January 2010 was the warmest January on record (see NASA: After Warmest Year on Record, Southern Hemisphere Starts 2010 With Record-Shattering January, 17 Feb 2010).

Online Resources:

NASA’s Earth Observatory:

Mertz Glacier.  MODIS image from 26 September 2001, 23:00.  From the U.S. National Snow and Ice Data Center.

Massive iceberg calves from the Mertz Glacier. Press release (26 Feb 2010) from Australian Antarctic Division.

National Snow and Ice Data Center:

Antarctic Climate & Ecosystems Cooperative Research Centre. “The ACE CRC is a unique collaboration between core partners the Australian Antarctic Division, CSIRO Marine and Atmosphere, the University of Tasmania, the Bureau of Meteorology and a consortium of supporting partners. It is funded by the Australian Government’s Cooperative Research Centre Program. The ACE CRC’s mission is to understand the crucial role played by Antarctica and the Southern Ocean in global climate, and the impacts of climate change on Australia and the world, and to inform governments, industry, the community and scientists about climate change to guide our future.”

Modeling water mass formation in the Mertz Glacier Polynya and Ad©lie Depression, East Antarctica.  By Marsland, S. J., N. L. Bindoff, G. D. Williams, and W. F. Budd in J. Geophys. Res., 109, 4 November 2004.

State of Antarctica: red or blue? Realclimate, 21 January 2009.

What’s Happening: Another Massive Iceberg is Born [PDF] .  By Neal Young in Australian Antarctic Magazine, Spring 2002.

WWF:

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19 Responses to Another massive iceberg is calved in Antarctica, with implications for local ocean circulation and wildlife

  1. Fran Grant says:

    Thanks very interesting. The displacement of the iceberg in terms of tons of water doesn’t vary. The displacement doesn’t change after melting. The displacement doesn’t change based on it being attached or detached.

    [JR: Quite true. But opening up glacial tongues may allow the ice behind it to accelerate.]

  2. Leif says:

    The article touched upon the food resource disruption a bit and I would like to expand some if I may.

    Sea ice, although different than glacial tongues is adversely affected by a warming climate as well and is disappearing at an astounding rate. The bottom face of sea ice is home to alga that in turn is food for krill, the base of the Antarctic food chain, from penguins to whales. The disappearance of the sea ice is the same as removing huge, gigantic even, fields of food from the access of people. In late 2004 an article,
    .abc.net.au/science/news/enviro/default.htm, (no longer active,)
    estimated an 80% loss in Antarctic krill at that time. Six long years ago…

  3. James Newberry says:

    RE: Joe’s “the ice behind it”

    Greenland icecap: approx. 700,000 cubic miles (20 feet sea rise)
    West Antarctica: similar to Greenland
    East Antarctica: approx. 7,000,000 cubic miles (200 feet sea rise)

    Where is my nuclear bailout bucket, must be downstairs in the floodwaters. Pass the new legislative debt bill please, I’ll leave the tip. Doesn’t that coal carbon (dioxide) you are breathing smell like money? As we’re a bit underwater financially speaking, better get adapting for the real thing. Maybe waterproof money?

  4. paulm says:

    Joe, it would be useful to break down some of your categories some more – like science could have sea level. A sub-level or tag of ‘best’ could also help refine the categories to the must read articles for each one.

    [JR: Yes, I need to do that.]

  5. Catchblue22 says:

    I’m reading in the popular news reports that this is not directly related to climate change. To quote

    “The calving (break) itself hasn’t been directly linked to climate change but it is related to the natural processes occurring on the ice sheet,” Rob Massom, a Tasmania-based senior scientist at the Australian Antarctic Division and the Antarctic Climate and Ecosystems Cooperative Research Center, told Reuters.”

    On what basis are such statements made? Is it because this is just a case of cyclical sea ice breaking off? I really wish news reports would give more scientific detail instead of merely reporting quotations.

  6. Tess says:

    Leif,

    The article you referred to is here: http://www.abc.net.au/news/stories/2004/11/04/1234442.htm

    I looked it up because I was wondering what year was the reference point for saying we had, by 2004, experienced an 80% drop in krill. The answer is 1976.

    Cheers
    Tess

  7. Jim Eager says:

    Fran Grant said: “The displacement doesn’t change after melting.”

    Ah, but it does, albeit only very slightly, because the iceberg consists of frozen *fresh* water floating in denser sea water.

    See: Melting of Floating Ice Will Raise Sea Level
    http://www.physorg.com/news5619.html

  8. GFW says:

    Leif, given that we are talking about Antarctica, why do you say “Sea ice […] is disappearing at an astounding rate”? Antarctic sea ice is generally tracking above average, although within 2-sigma bounds. I don’t expect that to be true 20y from now, but it is true now.

  9. Leif says:

    #8: Sea ice in the Antarctic behaves all together different from the Arctic in that it does melt back a lot each summer. It builds up around the perimeter of the Antarctic continent each winter and melts or breaks up each summer for the most part. Perhaps there is a shorter algae growing season associated with earlier breakup or something else.

  10. Lewis Cleverdon says:

    Quote:
    “The future position of the two giant icebergs will likely affect local ocean circulation, the extent (and timing?) of the polynya, sea ice production, and deep water formation…This calving is indeed a unique in-situ sensitivity experiment that will help to evaluate the climatic impacts of this region on the large scale ocean circulation.”

    While I’m all for ‘in-situ sensitivity experiments’ as a rule, this one seems to be on a rather awkward scale – that is, planetary circulation could be obstructed, leaving the researchers somewhat starved.
    Thus I’d be tempted to run an alternative experiment, one with explosive charges at one mile grid intervals, to see how much the resulting rise in the ice’s ratio of surface area to volume would hasten its rate of melting.

    Can anyone explain whether fragmenting the bergs would help, further hinder or make no difference to the ecologies they threaten ?

    If fragmenting them would reduce the threat they pose, then the fact that this would be a first effort in internationally agreed geo-engineering would need to be faced. Personally I doubt whether its impassioned opponents would cut any ice against the penguins’ loyal screen fans. Who could stand the sequel “April of the Penguins” where they died en masse of starvation due to a campaign to Save the Icebergs ?

    Regards,

    Lewis

  11. hi joe,

    all the articles i’ve seen on this state that it’s not caused by climate change. i understand that this was a collision from an already floating iceberg to a fixed tongue, but surely the general breakup of the west antartic coast is very much a climate change phenomenon. i’m not an expert, but that seems logical to me…?

    (great site BTW – don’t know how you find the time!)

  12. Bill Waterhouse says:

    I saw the report where one glaciologist reportedly said the breakup wasn’t caused by warming. Query whether he was being conservative and really said that one couldn’t be sure it was caused by warming. Seems like it would be entirely consistent with warming, wouldn’t it?

    Also wondering if the tsunami from the Chilean earthquake might help break up more Antarctic ice sheets?

  13. Rabid Doomsayer says:

    I don’t get how the ice bergs staying in place will greatly change things. Why is a static iceberg so different to a floating glacial tongue to the local environment?

    Just because I don’t understand it, does not mean it isn’t so. As always very interesting. Thanks Joe.

  14. Leif says:

    I have a friend that is project director on an Antarctic research vessel that is currently steaming back to Chile. They expect disruption to there travel plans as their Port of Call is Santiago. I will ask about the above discussion and seek enlightenment when I meet with him in April.

  15. Richard Brenne says:

    Just some related (sort of) tidbits:

    Because the sun is so low in Antarctica, more solar melting occurs on the ice-cliffs facing north and the sun than on flat horizontal surfaces.

    Jim Hansen points out that when the Greenland (often a mile, sometimes two) and East Antarctic (often two miles) ice sheets begin to melt, ultimately their being at lower elevations will accelerate the melting rate if all other factors were equal.

    Peter Clark of Oregon State has a paper (let’s see, I had it here somewhere) where he says that the gravitational pull of all the West Antarctic ice means that when it melts, the ocean water retreating due to less gravitational pull could mean eight or more inches of additional sea level rise at higher latitudes like those of the U.S.

    The Mertz glacier was named after Fred and Ethel Mertz who were stranded there during a particularly ridiculous scheme of Lucy’s.

  16. Christopher S. Johnson says:

    Can I get some clarification? Every news report I have seen about this has said that, in this case, these particular break-ups are not from global warming. These articles didnt feel like tabloid Daily Mail crap either. So I’ve avoided reposting this story to my friends and Facebook page. Any info for me on this? Thanks.

  17. Leif says:

    New from Environmental News Network. Changing Antarctic food web and ramifications there of.

    http://www.enn.com/climate/article/41063

  18. Leif says:

    #16, Chris: For starters, recall that almost every “news” story you have read states that AGW is a fabrication of delusional scientist and liberal tree huggers. Look at the evidence and meditate for awhile.

  19. fj2 says:

    re: This calving is indeed a unique in-situ sensitivity experiment . . .”

    Global warming has often been described by scientists as one experiment they’d prefer not to do.