Spike in phytoplankton biomass in Greenland Sea during 2009 and the correlations among chlorophyll-a, aerosol optical depth and ice cover

Abstract

The distributions and correlations of chlorophyll-a (Chl-a), aerosol optical depth (AOD) and ice cover in the southeast Arctic Ocean-Greenland Sea (10׭10Ŭ 70୸0Ω between 2003 and 2009 were studied using satellite data and statistical analyses. Regression analysis showed correlations between Chl-a and AOD, Chl-a and ice cover, and AOD and ice cover with different time lags. The time lag of Chl-a and AOD indicated their long-term equilibrium relationship. Peaks in AOD and Chl-a and generally occurred in May and July, respectively. Despite the time lag, the correlation between Chl-a and AOD in the study region was as high as 0.7. The peak gap between Chl-a and AOD shifted for about 6 weeks during 2003-2009. In the summer and autumn of 2009, Chl-a and AOD levels were much higher than during the other years, especially in the northern band of the study region (75୸0Ω. The driving forces for this localized increase in phytoplankton biomass could be mainly attributed to the very high rate of ice melting in spring and early summer and the high wind speed in autumn, together with the increased deposition of aerosol throughout the year. The unusually high AOD in the spring of 2003 was mainly due to a massive fire in Russia, which occurred in the first half of the year. Over the 7 years of the study, the sea surface temperature generally decreased. This may have been due to the release of dimethylsulfide into the air, excreted in large amounts from abundant phytoplankton biomass, and its subsequent reaction, form large amounts of aerosol, and resulting in regional cooling.