EESS talk on "Rethinking green icebergs"
Event details
| Date | 18.02.2020 |
| Hour | 12:15 › 13:00 |
| Speaker | Dr Stephen Warren, Professor, Dpt of Atmospheric Sciences, and Department of Earth & Space Sciences, University of Washington, Seattle, USA |
| Location | |
| Category | Conferences - Seminars |
Abstract:
Glacier ice, originating from snowfall, flows off the Antarctic Ice Sheet to float on the ocean as ice shelves. Ice crystals form in supercooled seawater beneath several Antarctic ice shelves; as they rise to the ice-shelf base they scavenge particles from the water and incorporate them into the growing basal ice. The resulting “marine ice” 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 white 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 yellow material (i.e., one that absorbs blue light), in combination with the blue of ice, can shift the wavelength of minimum absorption to green. Previously, dissolved organic carbon (DOC) had been proposed to be responsible 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 of green icebergs is caused more by iron-oxide minerals than by DOC. These icebergs travel great distances from their origin; when they melt they can deliver iron as a nutrient for phytoplankton in the Southern Ocean.
Short biography:
Stephen Warren is Emeritus Professor at the University of Washington in Seattle. His research concerns the interaction of solar radiation with snow, clouds, and sea ice, and their role in climate. He has carried out fieldwork in the Southern Ocean, the East Antarctic Plateau, Greenland, Svalbard, Canada, Siberia, and China with Australian, Russian, French, Danish, Norwegian, Chinese, and U.S. expeditions. He was Station Science Leader of the South Pole Station for 1992. He has about 135 publications, which have been cited about 16,000 times. He is a Fellow of AMS, AGU, and AAAS. He teaches classes on climate, atmospheric 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
Glacier ice, originating from snowfall, flows off the Antarctic Ice Sheet to float on the ocean as ice shelves. Ice crystals form in supercooled seawater beneath several Antarctic ice shelves; as they rise to the ice-shelf base they scavenge particles from the water and incorporate them into the growing basal ice. The resulting “marine ice” 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 white 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 yellow material (i.e., one that absorbs blue light), in combination with the blue of ice, can shift the wavelength of minimum absorption to green. Previously, dissolved organic carbon (DOC) had been proposed to be responsible 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 of green icebergs is caused more by iron-oxide minerals than by DOC. These icebergs travel great distances from their origin; when they melt they can deliver iron as a nutrient for phytoplankton in the Southern Ocean.
Short biography:
Stephen Warren is Emeritus Professor at the University of Washington in Seattle. His research concerns the interaction of solar radiation with snow, clouds, and sea ice, and their role in climate. He has carried out fieldwork in the Southern Ocean, the East Antarctic Plateau, Greenland, Svalbard, Canada, Siberia, and China with Australian, Russian, French, Danish, Norwegian, Chinese, and U.S. expeditions. He was Station Science Leader of the South Pole Station for 1992. He has about 135 publications, which have been cited about 16,000 times. He is a Fellow of AMS, AGU, and AAAS. He teaches classes on climate, atmospheric 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
Practical information
- General public
- Free
- This event is internal
Organizer
- EESS - IIE
Contact
- Prof. Anders Meibom, LGB