Published on December 18th, 2009 | by Susan Kraemer1
Iceberg Visits Australia as 10,000 Year Old Ice Breaks Off Antarctic
Another huge hunk of the Antarctic has broken off, and journeyed to within a thousand miles of the coast of Australia. This one is twice the size of Manhattan, but it is not the first huge chunk to go.
Larsen A collapsed abruptly in 1995. After the retreat of the Prince Gustav and the dramatic break-up of the Larsen-A ice shelves the British Antarctic Survey presented evidence that these events were caused by climate change.
Then, in 2000 an iceberg half the size of Wales broke off, and in 2002 the Larsen B ice shelf broke off.
A paper published in Nature in 2005 Stability of the Larsen B ice shelf on the Antarctic Peninsula during the Holocene epoch found that Larsen B ice shelf had been thinning throughout the Holocene, and the recent prolonged period of warming in the Antarctic Peninsula region in combination with the long-term thinning, led to the collapse.
In total, about 25,000 sq km of ice shelves have been lost, changing the maps of Antarctica. Ocean sediments indicate that some shelves had been in place for at least 10,000 years.
When the Wilkins Ice Shelf broke off in January this year; David Vaughn; a BAS glaciologist was widely quoted as saying “This ice shelf and the nine other shelves that we have seen with a similar trajectory are a consequence of warming.”
In the last few months, icebergs have been sighted off the coast of New Zealand. Some smaller ones have even made it to landfall on the frigid West Coast of the South Island.
A week ago, the British Antarctic Survey put out a press release noting in part that the largest ocean current on Earth (the Antarctic Circumpolar Current) has warmed faster than the global ocean as a whole.
For Antarctica as a whole, icebergs are normal events and do not indicate warming. However, according to Neal Young, Glaciology & Remote Sensing, Continental Ice Sheet Program, Antarctic CRC & AAD:
“There has been a dramatic decrease in the area of relatively small ice shelves fringing the Antarctic Peninsula over several decades.”
“These changes have accompanied a warming of several degrees observed since the 1940s in the Peninsula region, with mean summer temperatures approaching 0°C, and significant melt water production on the surface of many of the ice shelves.
Re-freezing in crevasses of melt-water runoff has progressively weakened the structure of those shelves.
Observations of their breakage and melt rates as they drift into progressively warmer waters provides information on the probable impact on the ice shelves of warmer temperatures in the air or polar waters accompanying a climate change.”
This week Antarctic Treaty nations met to devise more rigorous ship-building codes to better protect themselves from future iceberg attack. In 2007 a Canadian cruise ship was struck by a traveling iceberg and sank.