Seminar by: Stephen Warren (University of Washington, Seattle, USA)
The mystery of green icebergs – and their surprising importance
Abstract: 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. Icebergs of marine ice vary in color from blue to green, depending on the nature and abundance of foreign constituents in the seawater that became trapped in the ice as it grew. Red or yellow particles from the seawater, in combination with the blue of ice, can shift the color to green. Several wrong explanations were proposed over the years, including our own wrong explanation from 1993 that the green color was due to dissolved organic carbon. The recent finding of large concentrations of iron in marine ice from the Amery Ice Shelf suggests that the color of green icebergs is instead caused by iron-oxide minerals from glacier-flour. These icebergs travel great distances from their place of origin; when they melt they can deliver iron as a nutrient to the Southern Ocean.
Reference: Warren, S.G., C.S. Roesler, R.E. Brandt, and M. Curran, 2019: Green icebergs revisited. J. Geophys. Res. (Oceans), 124, doi:10.1029/2018JC014479.
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The GeoHyd seminars are normally held in Auditorium 2 in the Geology Building, Blindern (map) but it is also possible to follow some of the seminars on Zoom.
Videolink to the lectures will be sent to the e-mail list geohyd-alle@geo and geohyd-info@geo. If you want to subscribe to the geohyd-info@geo mailing list send an email to Anita Sørlie.
About the seminar series
The talks in GeoHyd Lunch Seminar Series are offered by the Section for Geography and Hydrology (GeoHyd), Dept. of Geosciences, University of Oslo. The seminars are announced as lunch seminars so bring your lunch if you want to.
The seminars are open for everyone interested, and especially students are welcome.
The Lunch Seminar Team
– Anita and Chong-Yu