An apparent continuing increase in Antarctic ‘superblooms’ in ice

Abstract

Medium Resolution Imaging Spectrometer (MERIS) satellite imagery of areas of mixed open water and ice near Antarctica shows an increase of a particular type of phytoplankton bloom by about a factor of 4 during the period 2003–2012. The increase has been mostly due to the detection of blooms over a larger area, increasing from about 24,000 km2 in 2003 to 100,000 km2 in 2012, but with some indication also of increasing bloom intensity. Blooms of this type have been previously identified as consistent with ‘superblooms’ near melting ice shelves, but can also be associated with newly forming ice. They occur in February to April of each year, with peak intensity in March, when new ice is starting to form. Although the total count shows a fairly steady increase, the blooms tend to occur at different longitudes in different years. Cause of the rapid increase is unclear. In 2011, a major bloom event was observed on 6 days in March in the Bellingshausen Sea, centred at 71.7° S, 89.0° W. This covered an area of 12,800 km2 and contributed 30% of the total bloom signal for the year.