Are phytoplankton blooms occurring earlier in the Arctic?


M. Kahru, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA, tel. +1 858 534 8947, fax +1 858 822 0562, e-mail:


Time series of satellite-derived surface chlorophyll-a concentration (Chl) in 1997–2009 were used to examine for trends in the timing of the annual phytoplankton bloom maximum. Significant trends towards earlier phytoplankton blooms were detected in about 11% of the area of the Arctic Ocean with valid Chl data, e.g. in the Hudson Bay, Foxe Basin, Baffin Sea, off the coasts of Greenland, in the Kara Sea and around Novaya Zemlya. These areas roughly coincide with areas where ice concentration has decreased in early summer (June), thus making the earlier blooms possible. In the selected areas, the annual phytoplankton bloom maximum has advanced by up to 50 days which may have consequences for the Arctic food chain and carbon cycling. Outside the Arctic, the annual Chl maximum has become earlier in boreal North Pacific but later in the North Atlantic.