Polar Research at UW Oceanography

Arctic oceanography and sea ice research at the University of Washington's School of Oceanography.

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The Chukchi polynya: measuring ice production with SSM/I

In their 2003 paper, Observations of Ice Thickness and Frazil Ice in the St. Lawrence Island Polynya from Satellite Imagery, Upward Looking Sonar and Salinity/Temperature Moorings, Drucker, Martin and Moritz validated estimates of thin ice thickness using AVHRR against in situ measurements from Upward Looking Sonar (ULS) moorings below the St. Lawrence polynya. While this method gives us the basis for satellite measurement of thin ice thickness in a large coastal polynya, it is limited to clear-sky conditions.

Martin, Drucker, Kwok and Holt, in their 2004 paper Estimation of the thin ice thickness and heat flux for the Chukchi Sea Alaskan coast polynya from Special Sensor Microwave/Imager data, 1990-2001, use concurrent AVHRR , SSM/I and RADARSAT imagery from the Alaskan Chukchi coast polynya in the winter of 2000 to map SSM/I 37V/H brightness temperature ratios to ice thickness, and show that the method is valid for thin ice up to 10 cm in thickness. Because the SSM/I 37GHz channels are insensitive to atmospheric water, the R37 -> h map is not limited to clear-sky conditions. Combining this with meteorological data from the National Centers for Environmental Prediction (NCEP) and the International Arctic Buoy Program (IABP) , estimates of daily winter heat flux and annual ice production from this large perennial polynya are derived for 1990-2001.

Martin, S., R. Drucker, R. Kwok, and B. Holt
Estimation of the thin ice thickness and heat flux for the Chukchi Sea Alaskan coast polynya from Special Sensor Microwave/Imager data, 1990-2001
Journal of Geophysical Research, Vol. 109, C10012, doi:10.1029/2004JC002428, 2004

ABSTRACT: One of the largest Arctic polynyas occurs along the Alaskan coast of the Chukchi Sea between Cape Lisburne and Point Barrow. For this polynya, a new thin ice thickness algorithm is described that uses the ratio of the vertically and horizontally polarized Special Sensor Microwave/Imager (SSM/I) 37-GHz channels to retrieve the distribution of thicknesses and heat fluxes at a 25-km resolution. Comparison with clear-sky advanced very high resolution radiometer data shows that the SSM/I thicknesses and heat fluxes are valid for ice thicknesses less than 10­20 cm, and comparison with several synthetic aperture radar (SAR) images shows that the 10-cm ice SSM/I ice thickness contour approximately follows the SAR polynya edge. For the twelve winters of 1990­2001, the ice thicknesses and heat fluxes within the polynya are estimated from daily SSM/I data, then compared with field data and with estimates from other investigations. The results show the following: First, our calculated heat losses are consistent with 2 years of over-winter salinity and temperature field data. Second, comparison with other numerical and satellite estimates of the ice production shows that although our ice production per unit area is smaller, our polynya areas are larger, so that our ice production estimates are of the same order. Because our salinity forcing occurs over a larger area than in the other models, the oceanic response associated with our forcing will be modified.
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Concurrent satellite images of the Chukchi polynya on 2000 day 72.