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a core project of
2018WCRPspon col July2018 01 1

SAckley - Antarctic Sea Ice Observing and Field Campaigns


Antarctic Sea Ice Observing and Field Campaigns
- Stephen Ackley, University of Texas San Antonio, USA

Antarctic sea ice, unlike the Arctic, has not been traversed routinely by nuclear submarines with upward looking sonar to measure ice thickness.  Therefore, the principal methods to obtain ice thicknesses on smaller (floe) scales have been by ice drilling or the use of hand-held EMI profilers.  On the large scale, Aspect visual observations, conducted by observers on the bridges of icebreakers, have provided, over thirty years, a method to see the regional-scale ice thickness variations and have provided the only records at the circumpolar scale through the late twentieth century.  Recent efforts on ice thickness have tried to use the laser altimeters from the ICESat 1 satellite from 2003-2009 and more recently from airborne lidar such as flown on the NASA IceBridge flights from 2009 until present.  Since altimeters only measure topside elevation of the snow cover on sea ice, recent field campaigns have focused on providing the correlation between top elevation and ice thickness in an effort to convert altimetric elevation measurements into a usable estimate of the ice thickness. The Antarctic and Arctic conversion algorithms differ principally because of the deeper snow and flooding of the snow ice interface (“negative ice freeboard”) that is widespread in the Antarctic sea ice zone.

Ice mass balance buoys in the limited deployments conducted in the Antarctic have shown how the flooded interface develops, from snow accumulations during winter, redistribution of snow cover in the high wind environment, and through melting of the ice cover from below during summer conditions.  The snow environment and the rapidly changing air temperatures due to the oceanic environment  cause high frequency fluctuations in the thermal regime of the ice cover and has been linked to rapid fluid flow changes resulting in a behavior of Antarctic sea ice  coined as a “biogeochemical reactor”.

Planned field campaigns will focus on understanding the unique role of Antarctic polynyas in sea ice production and water mass transformation, and providing Calibration/Validation for present airborne lidar elevation conversions to ice thickness and the anticipated launch of the satellite laser altimeter on ICESat 2 in 2016.  Buoy deployments in association with ship experiments will provide needed information on ice dynamics as well as seasonal development of ice thickness and internal structures.


Presentation given at the CliC Sea Ice Modeling and Observing Workshop held at the Fram Centre in Tromsø, Norway from 5 - 7 June 2013.

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