Papers Online - #153

On the Radiation Characteristics of Antarctic Sea Ice

Gerd Wendler1, Blake Moore2, Dorte Dissing2 and John Kelley2

1 Dept. of Geography, University of Canterbury, Christchurch, New Zealand
2 Geophysical Institute, University of Alaska, Fairbanks, Alaska, USA

Abstract

Radiative measurements were carried out continuously during a cruise from Australia to Antarctica during austral summer 1995/96. Both short-wave and long-wave radiative fluxes were measured. Some of the results are:

  • The incoming solar radiation had a mean value of 217 Wm-2; this was a relatively weak value due to the large amount of fractional cloud cover observed. The sun was for a large part of the trip, above the horizon for 24 hours a day.
  • The reflectivity varied widely, not only as function of sea ice concentration, but also as function of ice type.
  • Snow covered pack ice gave the highest albedo values ( 70%), while flooded sea ice and thin ice reflected much less ( 30%).
  • For each sea ice type, short term observations showed a good relationship between albedo and ice concentration.
  • The albedo increased with decreasing solar elevation.
  • The net long wave radiation was negative (mean -27 Wm-2); this small value is due to a high amount of fractional cloud cover. There was a weak diurnal variation with a maximum loss (-33 Wm-2) in the early afternoon.
  • On the average, the net radiation was positive for 17 hours, and negative for 7 hours a day. However, the duration of a positive balance depended strongly on the surface albedo.
  • 2. For the observed albedo values, modeling results showed that the net radiation was always positive when averaged over a day. The magnitude, however, depended strongly on the surface albedo, varying by more than the factor of three.

     

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Gerd Wendler
gerd@gi.alaska.edu
Date Last Modified: 4/30/00