Sea Ice Mass Balance in the Antarctic-SIMBA Drift Station

Project Description
This project was the International Polar Year sea ice drift station for Antarctic Sea Ice, a component of the overall project, Antarctic Sea Ice, endorsed internationally by the Joint Committee for IPY (www.ipy.org). Additionally, the buoys deployed were endorsed as an IPY contribution to the WCRP/SCAR International Programme on Antarctic Buoys (IPAB). The major goals of this study were to investigate the evolution of the sea ice cover in the Bellingshausen−Amundsen−Ross Seas during the late winter−summer periods. A ship−based study (NB Palmer) conducted in the Bellingshausen Sea focused on the first half of the period when the net radiation balance was still negative (Sept−Oct). The ship studies, including transit sampling stations and a drifting station were extended to include the remaining evolution of the ice cover into early summer using autonomous mass balance buoys and high temporal motion buoys, and complementary satellite measurements from the ICES at laser altimeter, RadarSAT SAR, and AMSR-E passive microwave instruments.

Work from the NB Palmer was a drifting station tied to an ice floe for 27 days in the Bellingshausen Sea during a 60 day cruise, Sept−Oct 2007. During the cruise and on the ice station, on−ice measurements were conducted on sea ice physical, biological and biogeochemical properties. The ice station work included time series measurements of these properties at two sites over the period of ice station occupation. CTD and trace metal casts were conducted in transit and at the ice station. Drifting ice mass balance buoys measuring snow and ice thickness changes, ice temperatures, CTD, and under ice spectral irradiance were deployed at the ice station site and continued to transmit autonomously for up to six weeks after the ice station work until early Dec 2007. At the ice station site, and also in transit to and from the main floe ice, surveys of snow and ice physical properties were conducted. The surveys consisted of horizontal transects measuring at intervals snow depth, ice thickness and the areal extent and thickness of flooded layers observed at the snow ice interface. Line measurements were repeated three times during the twenty seven day ice station period to determine changes in snow and ice properties and thickness. Swath bathymetry of the ocean bottom during drift station and transit was obtained and ADCP profiles were continuously recorded throughout the drift station and during transit.

Two other activities were conducted under the auspices of the SIMBA project.

Oden Cruise 2006-summer ice conditions. This first cruise of the Oden to McMurdo Sound in 2006 consisted of underway ice observations by this project of summer ice conditions across the Ross Sea during the transit. These observations were then used to validate AMSR-E passive microwave estimates of sea ice extent and concentration along the cruise track, other comparisons were made with satellite-based ice mapping of sea ice extent conducted by the National Ice Center during the period of the cruise.

Deployment of Ice Mass Balance buoy- Summer-Fall Transition in the Amundsen Sea One Ice Mass Balance buoy (IMB) that had been deployed during the drift phase of SIMBA in Oct 2007 and recovered at the end of the drift deployment was redeployed during the NB Palmer cruise to the Amundsen Sea in Jan-Feb 09.This buoy provided ice temperature, CTD, and ice and snow thickness information for seven weeks, from late summer-fall, contrasting with the spring-summer transition observed from the buoys deployed on the SIMBA drift station in 2007.