Abstract
Antarctic marine biological variability modulates climate systems via the biological pump. However, the knowledge of biological response in the Southern Ocean to climate variability still has been lack of understanding owing to limited ocean color data in the high latitude region. We investigated the surface chlorophyll concentration responses to the Southern annular mode (SAM) in the marginal sea of the Southern ocean using satellite observation and reanalysis data focusing on the austral summer. The positive phase of SAM is associated with enhanced and poleward-shifted westerly winds, leading to physical and biogeochemical responses over the Southern ocean. Our result indicates that chlorophyll has strong zonally asymmetric responses to SAM owing to different limiting factors of phytoplankton growth per region. For the positive SAM phase, chlorophyll tends to increase in the western Amundsen–Ross Sea but decreases in the D’Urville Sea. It is suggested that the distinct limiting factors are associated with the seasonal variability of sea ice and upwelling per region.
Highlights
Antarctic marine biological variability modulates climate systems via the biological pump
Owing to the extended period and seasonality, the physical responses to Southern annular mode (SAM) are changed in the Southern Ocean that asymmetric phytoplankton response to the SAM became more distinct in the marginal sea of the Southern Ocean, which was weakly shown on the regression between chlorophyll and SAM in Lovenduski and Gruber[14]
The atmospheric circulation changes are almost homogeneous in the zonal direction, the biological responses are zonally asymmetric to a large extent
Summary
Antarctic marine biological variability modulates climate systems via the biological pump. The mixed layer depth (MLD), net air-sea heat fluxes, sea ice, mesoscale eddies, and Atlantic meridional overturning circulation is strongly affected by SAM around the Southern O cean[5, 13, 15,16,17] These physical effects on the Southern Ocean could induce biogeochemical changes, such as changes in nutrient and phytoplankton concentration. We revisit biological responses depending on the SAM phase based on satellite observation and reanalysis data on an interannual timescale with a similar approach of physical and biogeochemical interactions in the Southern Ocean. These data are extended from 1998 to 2019 which are 10 years longer than that of Lovenduski and Gruber[14]. We discuss the implications of our results on the Southern Ocean
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