A huge ice shelf 25% larger than the island of Manhattan broke off of Canada's Arctic coast in 2005, according to a press release issued by researchers at the University of Ottawa's Laboratory for Cryospheric Research. The Ayles Ice Shelf, located on the northern coast of Ellesmere Island, was about 66 square kilometers in area and 100 feet thick. As of December 2006, the ice shelf had drifted about 50 km and was a big iceberg about 800 km south of the North Pole. It is expected to slowly melt over the next few years and drift into the Beaufort Sea, where it may pose a threat to shipping and oil and gas developments. Melt water from the giant new iceberg will not contribute significantly to sea level rise, since it was already floating on the ocean surface (think how ice cubes floating in a cup of water do not raise the level of the water after they melt). A slight sea level rise will occur, because the melting fresh water will displace denser salty ocean water. The addition of the ice shelf's fresh water to the Arctic Ocean will not freshen the ocean detectably, since the ice shelf will melt slowly and is a relatively small chunk of ice in a huge ocean.


Figure 1. October 21, 2003 image of the northern coast of Canada's Ellesmere Island, showing the location of the Ward Hunt Ice Sheet, which broke up in 200-2003, and the Ayles Ice Sheet, which broke away in August 2005. Image credit: NASA.


Figure 2. NASA Modis satellite image from August 13, 2005, showing the Ayles Ice Shelf detaching from Ellesmere Island.

The Ayles Ice Shelf actually broke off on August 13, 2005, and created tremors strong enough to be detected by seismographs 250 km away. The break off was not announced until researchers had time to study the event. The ice shelf was one of six large ice shelves remaining in the Canadian Arctic. The region's largest ice shelf, the Ward Hunt Ice Shelf, broke up in 2000-2003. In both cases, the warming of the average air temperature by 1.8 �C in the past 40 years is thought to be the cause. Unusually warm temperatures in 2005 proved to be the final blow to the ice sheet. The hot summer of 2005 led to the greatest loss of Arctic ice ever observed--about a 20% decrease over the levels observed in 1979, when reliable record keeping began. The ice shelves along the northern coast of Ellesmere Island have thinned 90% since they were discovered in 1906 by polar explorer Robert Peary.

While much of the past warming of the Arctic can be attributed to natural causes, a significant and growing portion of the warming is thought to be due to human-caused climate change, according to the Arctic Climate Impact Assessment (ACIA), a 2004 study compiled by 300 expert Arctic scientists. Considering that radiocarbon dating of driftwood on the Ayles Ice Shelf puts its age at 3,000 years old, it is unlikely that the shelf would have collapsed without the aid of warming from greenhouse gases emitted by humans. The Arctic is expected to warm another 2-4 �C by the end of the century, which should permanently destroy all the remaining ice shelves in the Arctic. These ice shelves hold a rare and unique ecosystem of cold-adapted organisms, and their loss will mean something irreplaceable and fascinating will be forever lost.