3-Decadal Changes in Sea Ice Melting and Freezing Pattern in Antarctica Using SSM/I Data
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RESEARCH ARTICLE
3-Decadal Changes in Sea Ice Melting and Freezing Pattern in Antarctica Using SSM/I Data K. K. Singh & V. D. Mishra & Sahil Sood & Manoj Kumar
Received: 15 February 2013 / Accepted: 22 April 2013 # Indian Society of Remote Sensing 2013
Abstract The present study aims to estimate the long term changes in sea ice areal extent (SIAE) around Antarctica using Special Sensor Microwave Imager (SSM/I) satellite data (1988–2011). Daily, weekly and monthly brightness temperature (TB) maps of Antarctica have been generated. Temporal variation in monthly averaged TB values of sea ice have been analyzed and an increasing trend is observed in TB. Sea ice concentration (SIC) values are estimated and the concentration class 0.85–0.95 is observed as the main contributor in sea ice areal extent during the Antarctic peak winter month i.e. September and October. SIC changes rapidly from October onwards and shows fast melting of sea ice, however, from April start of freezing has been observed. Continuous increase in SIAE is observed from February to September in all the analyzed years (1988–2011) data. In this observation period maximum SIAE is observed in September 1989 and minimum in February 1993. The Moderate Resolution Imaging Spectroradiometer (MODIS) data is used for the validation of SIAE values. SSM/I and MODIS estimated SIAE values are compared (R2 =0.98) and a relation between them is established by performing regression analysis. This relation is further used for the estimation of corrected SIAE K. K. Singh (*) : V. D. Mishra : S. Sood : M. Kumar Snow and Avalanche Study Establishment (SASE), Him Parisar, Plot No. 1, Sector-37A, Chandigarh 160 036, India e-mail: [email protected]
values. The monthly average sea ice extent maps of last three decades have been analyzed and a shift in onset of freezing of sea ice has been observed. The period of frozen sea has also been observed as decreased. Keywords SSM/I . MODIS . Brightness temperature . SIAE and SIC
Introduction Sea ice cover acts as a barrier between ocean and atmosphere and thus affects the energy, gases and momentum transfer between them. The growth and melting of sea ice are major factors responsible for controlling the seasonal cycle of the air temperature and the upper ocean salinity in the polar regions. The changes in sea ice areal extent (SIAE) and the variation in ocean flux are interrelated and it has been proven that sea ice cover is one of the important factors controlling the ocean heat flux (Allison 1979). As the climate of high latitudinal areas is affected by annual cycles of sea ice cover and due to their interannual variations (Barry et al. 1993), this has further raised the interest of various researchers in monitoring and analyzing sea ice around the Antarctic and the Arctic. In the Antarctic due to cold and hostile climate and fluctuating sea ice conditions, in-situ data collection is very difficult. However, some automatic data collection methods i.e. Automatic Weather Station (AWS) were used but still monitoring of differe
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