Abstract

COMPAGNUCCI, Rosa H.  and  BARREIRA, Sandra. Climatology of sea ice concentration spatial variability over Bellingshausen, Amundsen and Weddell Seas. Meteorologica [online]. 2005, vol.30, n.1-2, pp.55-76. ISSN 1850-468X.

In this paper the most frequent spatial patterns of sea ice concentration anomalies (SICA) over the Amundsen, Bellingshausen and Weddell Seas have been obtained from monthly mean values of sea ice concentrations provided by the Scanning Multichannel Microwave Radiometer and the Special Sensor Microwave/Imager of NASA Goddard Space Flight Center for the period 1979 2000. Using analysis of Principal Components (PCs) in T-Mode rotated Varimax, six PCs were obtained. Therefore, a total of 12 patterns were found with six in direct mode (SICA of the same sign that the PC) and six in inversely (SICA of opposite sign to the PC), that classify 95.5 % of the monthly fields. Three PCs describe the most frequent winter-spring cases (period with major concentration and expansion of sea ice) and three PCs correspond to summer-autumn (minor concentration and retraction of the field of ice). Winter-spring months have mainly situations close to the first and second PCs. The 2°PC shows a 30 ° counter wise rotation with respect to the 1°CP and both present dipole anomalies between the seas at both sides of the Antarctic Peninsula. These two components display a recurrence of approximately 4 years in which alternatively the exterior region of the Weddell Sea has conditions of sea ice above the mean values meanwhile, in the north of the Amundsen Sea, the anomalies are negative and vice versa. The most frequent condition with an annual summer - autumn recurrence (3ºCP) is also a dipole but between the interior of the Weddell and the coastal region of Amundsen-Bellingshausen because these is the region where the sea ice is presented in this epoch of the year. The 4 º, 5 º and 6 º components refer to different, and not descript in the literature, conditions of SICA. The summer-autumn PCs, fundamental for the Antarctic navigation, show a change of behavior occurred at the end of the 80s years, in that the Amundsen and Bellingshausen Seas passed of having bigger to minor concentrations of sea ice. The SICA spatial distribution during the mature phases El Niño showed great variability among events and in some cases have opposite behavior for different events. The same occur for La Niña. The influence of the ENSO cycle is relatively clear only for the winter that follows the summer mature phase of the El Niño or La Niña.

Keywords : Sea ice concentration; Weddell; Bellingshausen; Amundsen spatial patterns; Principal component analysis; El Niño.

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