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PRODID:-//Memento EPFL//
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SUMMARY:EESS talk on "Rethinking green icebergs"
DTSTART:20200218T121500
DTEND:20200218T130000
DTSTAMP:20260510T202330Z
UID:77ff080d47c4b5ee71846705f18199684bee6b72abc461da60e9cae0
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Stephen Warren\, Professor\, Dpt of Atmospheric Sciences\, 
 and Department of Earth & Space Sciences\, University of Washington\, Seat
 tle\, USA\nAbstract:\nGlacier ice\, originating from snowfall\, flows off 
 the Antarctic Ice Sheet to float on the ocean as ice shelves.  Ice crysta
 ls form in supercooled seawater beneath several Antarctic ice shelves\; as
  they rise to the ice-shelf base they scavenge particles from the water an
 d incorporate them into the growing basal ice.  The resulting “marine i
 ce” can be ~100 m thick\; it differs from sea ice in that it is clear\, 
 desalinated\, and bubble-free.  At the front of the ice shelf\, icebergs 
 break off.  The upper part of a composite iceberg is glacier ice\, which 
 appears bluish-white\, intermediate between the blue of pure ice and the w
 hite of snow\, because glacier ice contains numerous bubbles that scatter 
 light. The lower part is marine ice\, which can be exposed to view if the 
 iceberg capsizes.  The marine-ice part varies in color from dark blue to 
 dark green\, depending on the nature and abundance of foreign constituents
  in the seawater that became trapped in the ice as it grew.  A red or yel
 low material (i.e.\, one that absorbs blue light)\, in combination with th
 e blue of ice\, can shift the wavelength of minimum absorption to green. 
  Previously\, dissolved organic carbon (DOC) had been proposed to be respo
 nsible for the green color.  Subsequent measurements of low DOC values in
  green icebergs\, together with the recent finding of large concentrations
  of iron in marine ice from the Amery Ice Shelf\, suggest that the color o
 f green icebergs is caused more by iron-oxide minerals than by DOC.  Thes
 e icebergs travel great distances from their origin\; when they melt they 
 can deliver iron as a nutrient for phytoplankton in the Southern Ocean.\n\
 nShort biography:\nStephen Warren is Emeritus Professor at the University 
 of Washington in Seattle. His research concerns the interaction of solar r
 adiation with snow\, clouds\, and sea ice\, and their role in climate. He 
 has carried out fieldwork in the Southern Ocean\, the East Antarctic Plate
 au\, Greenland\, Svalbard\, Canada\, Siberia\, and China with Australian\,
  Russian\, French\, Danish\, Norwegian\, Chinese\, and U.S. expeditions. H
 e was Station Science Leader of the South Pole Station for 1992. He has ab
 out 135 publications\, which have been cited about 16\,000 times. He is a 
 Fellow of AMS\, AGU\, and AAAS. He teaches classes on climate\, atmospheri
 c radiation\, glaciology\, and scientific writing\, and has won two awards
  for excellence in teaching. He has supervised 8 M.S. students and 12 Ph.D
 . students\n 
LOCATION:GR A3 30 https://plan.epfl.ch/?room==GR%20A3%2030
STATUS:CONFIRMED
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