Atmospheric factors influencing biological productivity in the Antarctic polynyas, derived from satellite and reanalysis data

Abstract

Antarctic coastal polynyas are the most productive area in the Southern Ocean, playing a significant role in a polar ecosystem. Understanding polynya properties is important because changes in polynya's environment can alter, or even disrupt, the polar food web. Nevertheless, there are still many unknown aspects of polynyas and its subsequent effects in the ecosystem. Based on satellite and atmospheric reanalysis data for 1998？2016, roles of atmospheric forcing on phytoplankton dynamics are examined. We find that chlorophyll-a (chl-a) has a noticeable year-to-year variability and its responses to atmospheric forcing differ regionally. That is, winds have a strong correlation with chl-a in the west Antarctic polynyas since strong winds tend to increase nutrient entrainment from subsurface water. A cloud cover is suggested to influence chl-a variability with a strong inverse correlation in the Weddell Sea and a moderate inverse correlation in the Amundsen Sea. We also find that chl-a decreases for 1998？2016 in the Amundsen Sea and Weddell Sea, which implies that a large amount of glacier melt water is likely to decrease chl-a by enhancing oceanic stratification, whereas iron supply from recent higher ice melt would not directly affect such a long-term chl-a change.