When a
glacier flows in its lethargic way out to sea,
tidal forces often break it up into
icebergs. But sometimes the ice stays together and forms a long block that sticks out on the surface of the water. This long block is called an
ice tongue. (I guess the
Antarctican isolation has its linguistic consequences.) Of all the tongues,
Drygalski wins for fame, coolest name, and most recent endangerment.
This particular tongue is the output of the David glacier on the Western shore of the Ross sea, right by the Prince Albert mountains. Though these things are constantly changing as they calve new icebergs of their own, at the time of this write up the Drygalski tongue was a whopping 40 kilometers in length and about 10 in width. That's larger than Manhattan island. Along its length it varies between 50 and 200 meters thick.
The tongue was first discovered by British explorer Robert Falcon Scott in the middle of his legendary 1901-03 expedition that failed to reach the South Pole but found the enormous Ross Ice Shelf. Since then the ice tongue has been measured and it has been growing steadily in this time between 50 and 900 meters a year. Penguin guano on the tongue has been carbon dated and it may over 4000 years old.
The Drygalski ice tongue had for the past few months (March 2006) been at risk of a colossal impact, as the world's single largest floating object, a 70-kilometer-long iceberg named B15-A, slowly made its way on a collision course with it, right near the McMurdo Research Station. This would be a globally significant event since a free-floating iceberg of this size would be enough to alter ocean currents and affect the arctic climate. Near the end of January 2005, however, B15-A came to a halt in shallow waters near the tongue a few kilometers from impact. This could have been a major ecological and economic disaster as the tongue keeps a huge portion of sea north of it unfrozen and thereby life-sustaining and navigable. It survived, but B15-A's new parking spot, if long lived, may have ecological consequences as it is causing a buildup of surface fast ice and blocking penguins and other arctic life forms from getting from the tongue to the open sea.
For only 13,000 USD you too can get up close and personal with the ice formation, one of the many marvelous stops on Expedition Cruise's month-long tour titled "Khlebnikov: The Wonders of the Ross Sea", scheduled for winter 2005-06. If you just can't wait that long or can't afford to drop a quick 13K, you'll have to satisfy yourself with the numerous online images:
- http://landsat.usgs.gov/gallery/images/Landsat_Gallery_406_1_full.jpg
- http://earthobservatory.nasa.gov/NaturalHazards/Archive/Jan2005/Drygalski.TMOA2005013_lrg.jpg
- http://earthobservatory.nasa.gov/Newsroom/NewImages/Images/Drygalski_ASAR_2005053_lrg.jpg
See the near-miss at:
- http://www.nasa.gov/vision/earth/lookingatearth/ice_berg_ram.html
Sources:
- http://landsat.usgs.gov/gallery/detail/406/
- http://www.scoop.co.nz/stories/SC0501/S00011.htm
- http://www.innovations-report.com/html/reports/earth_sciences/report-39066.html
30 March 2006 Update: Loosened from global warming, gigantic (55x18.5 km) iceberg C-16 smashes into the tip of the tongue, knocking a chunk off, which becomes its own (13x11 km) iceberg, complete with a new name: C-25. Both wrap around to the northern part of the tongue.
Cool slide projection of the impact
http://www.esa.int/esaEO/SEMFYFNFGLE_index_0.html