Sea Ice Mass Balance in the Antarctic - Remote Sensing

Monthly average sea ice concentration for February to May, 2007 and June to September 2007 show regionally where the ice edge for the month in question equator ward/pole ward of the 29-year mean. Based on the 29 year time series (1979-2007), the following rankings were observed for monthly averaged Southern Ocean sea ice extent from January to August 2007: January 2007 was the fourth lowest January observed over 1979-2007; February the second lowest; March and April the fourth lowest; May the second lowest, June the fourth lowest, July the third lowest, and August the lowest. In general the western Weddell and western Ross Sea regions showed near to above average sea ice extent. In contrast, the Bellingshausen-Amundsen Sea region showed well below average sea ice extent, with the following monthly rankings: January and February were the fourth lowest; March was the lowest, April was the second lowest; May through July was the lowest; and August was the fifth lowest. Sea ice extent averaged over September 1-18, 2007 (the data available before leaving port) showed September to be the lowest over 1979-2007 for the Bellingshausen-Amundsen Sea region. However, September’s ranking may change slightly with the inclusion of days 19-30 in the monthly average.

The dataset includes monthly averaged sea ice concentrations for Feb-May and Jun-Sep with dotted contour outlines that resemble the ice edge for the month in question. As seen in the monthly sea ice concentration images, the ice edge in the Bellingshausen-Amundsen Sea region was well pole ward during the months of sea ice advance (Feb-Sep). Using the daily sea ice concentration data, the day of sea ice advance (in year day) was recorded for every location in the daily sea ice concentration images for each year. Anomalies in the timing of sea ice advance were determined by subtracting the mean (1979-2007) day of sea ice advance from the day of advance for each location in 2007. The advance in most of the Bellingshausen and Amundsen Sea region was up to 80+ days later than the 29-year mean. Sea ice advance also was late in the East Antarctic sector between 90-130E where the RVIB Aurora Australis conducted an IPY research cruise during August-September.

Data set also includes brightness temperatures, sea ice concentration differences between enhanced NASA Team (NT2) and Bootstrap Basic Algorithm (BBA), snow depth over sea ice, among other data. The 12.5 km sea ice concentration product is generated using two algorithms: the enhanced NASA Team (NT2) algorithm (Markus and Cavalieri 2000) for the Arctic and the Bootstrap Basic Algorithm (BBA, Comiso 1995) for the Antarctic. The quikscat data are given as backscatter coefficient in dB (log scale). The QuikScat instrument is a conically scanning radar that transmit and receive at both Horizontal and Vertical polarization. (HH is for transmitted and received horizontal polarization, VV for vertical). The POL images are the ratio of VV to HH. The HH and VV images are rather similar. Over the ocean the signals are strongly correlated with wind speed. Over the ice, the signal is more associated with ice type than ice concentration (older ice -> stronger backscatter (red)). Processes in the snow (grain size etc. can generate stronger backscatter (red areas) as well. The POL image normally gives a reasonable reliable ice extent (maximum limit of the ice). Eleven RADARSat (high resolution active microwave were also obtained over the area of the SIMBA cruise track during the time of the expedition and were used to correlate ice properties with shipboard observations taken at the same time.