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No. 87: May-Jun 1993

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The bottle-green icebergs of antarctica

Antarctic icebergs frequently incorporate sediments that turn them dark, even zebra-striped on occasion. But it is the bottle-green icebergs that provoke the most interest, for it is not certain why they are green. Is it due to intrinsic optical properties of the ice or impurities? A recent paper by J. Kipfstuhl et al suggests the latter and tells us where these translucent, strikingly green bergs originate.

"A comparison of samples from a translucent green iceberg with a core from the Ronne Ice Shelf revealed an excellent agreement in isotopic composition, crystal structure, and incorporated sediment particles. Marine shelf ice which constitutes the basal portion of some ice shelves is considered to be the source of green icebergs. It [the green ice] most likely results from 'ice pump' processes which produce large amounts of ice platelets in the water column beneath ice shelves. These subsequently accumulate and become compacted into bubble-free, desalinated ice."

The inclusions in the green ice are probably trapped by the accumulating platelets. Since the green ice is confined to the bottoms of the bergs, it becomes apparent only after the bergs capsize. The green icebergs in the Weddle Sea originate mainly from the Amery Ice Shelf.

(Kipfstuhl, J. et al; "The Origin of Green Icebergs in Antarctica," Journal of Geophysical Research, 97:20,319, 1992.)

Similar phenomenon. The ice calving from Alaskan glaciers is often a beautiful blue color -- the consequence of the ice's high density rather than inclusions. Alaskans export this ice to Japan where it is popular in drinks at tony parties!.

From Science Frontiers #87, MAY-JUN 1993. 1993-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:

Quotes

  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987