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Large‐Scale Ocean‐Atmosphere Interactions Drive Phytoplankton Accumulation in the Northern Antarctic Peninsula.

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Title: Large‐Scale Ocean‐Atmosphere Interactions Drive Phytoplankton Accumulation in the Northern Antarctic Peninsula.
Authors: Ye, Suwen1 (AUTHOR), Zhang, Zhaoru1,2,3,4 (AUTHOR) zrzhang@sjtu.edu.cn, Vihma, Timo5 (AUTHOR), Jiang, Mingshun6 (AUTHOR), Xie, Chuan1 (AUTHOR), Yu, Lejiang7 (AUTHOR), Smith, Walker O.1,2 (AUTHOR)
Source: Journal of Geophysical Research. Oceans. Mar2025, Vol. 130 Issue 3, p1-14. 14p.
Subject Terms: *Algal blooms, *Ocean temperature, Antarctic climate, Euphotic zone, Cloudiness
Abstract: The northern Antarctic Peninsula (NAP) region is a highly productive ecosystem that supports a large krill‐based food web. In summer 2006, the NAP region had substantially elevated phytoplankton biomass, with surface chlorophyll‐a concentrations that reached the greatest level during 2001–2023. Using the long‐term in situ data from the U.S. Antarctic Marine Living Resources program, satellite observations, and ERA5 reanalysis products, the mechanisms of the elevated chlorophyll‐a anomalies in summer 2006 were analyzed. The results suggest that the position of the Amundsen Sea Low (ASL) shifted considerably westward that summer, resulting in strong positive sea level pressure anomalies west of the NAP, which induced southerly wind anomalies and reduced the advection of moist airflow toward the NAP. This in turn reduced the cloud coverage and increased photosynthetically available radiation over this region, which directly increased the phytoplankton photosynthesis. The intensified radiation also increased the ocean temperature and strengthened stratification, which increased phytoplankton growth rates and allowed phytoplankton to accumulate in the upper euphotic zone. This work underlines the important role of coupled atmospheric‐oceanic processes in generating large phytoplankton biomass in the NAP region. Plain Language Summary: The sea around the northern Antarctic Peninsula (NAP) is known for its high productivity. According to in situ measurements and satellite observations, phytoplankton biomass in the NAP was anomalously high in summer 2006, as indicated by the surface concentrations of chlorophyll‐a being 2–3 times greater than the average. These high chlorophyll‐a anomalies were related to the westward shift of the Amundsen Sea Low, a climatological low‐pressure center that exerts great influence on the West Antarctica climate. The resulting positive pressure anomalies west of the NAP modulated the cloud cover and light over the study region by affecting the wind field and humidity. The increased light and the strengthened stratification generated this summer 2006 phytoplankton bloom. Key Points: Anomalous elevated chlorophyll‐a concentrations occurred in the northern Antarctic Peninsula region in summer 2006The combination of strong stratification and enhanced irradiance availability stimulated phytoplankton growth and accumulationStronger stratification and irradiance were caused by low cloudiness resulting from the dramatic westward shift of the Amundsen Sea Low [ABSTRACT FROM AUTHOR]
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Abstract:The northern Antarctic Peninsula (NAP) region is a highly productive ecosystem that supports a large krill‐based food web. In summer 2006, the NAP region had substantially elevated phytoplankton biomass, with surface chlorophyll‐a concentrations that reached the greatest level during 2001–2023. Using the long‐term in situ data from the U.S. Antarctic Marine Living Resources program, satellite observations, and ERA5 reanalysis products, the mechanisms of the elevated chlorophyll‐a anomalies in summer 2006 were analyzed. The results suggest that the position of the Amundsen Sea Low (ASL) shifted considerably westward that summer, resulting in strong positive sea level pressure anomalies west of the NAP, which induced southerly wind anomalies and reduced the advection of moist airflow toward the NAP. This in turn reduced the cloud coverage and increased photosynthetically available radiation over this region, which directly increased the phytoplankton photosynthesis. The intensified radiation also increased the ocean temperature and strengthened stratification, which increased phytoplankton growth rates and allowed phytoplankton to accumulate in the upper euphotic zone. This work underlines the important role of coupled atmospheric‐oceanic processes in generating large phytoplankton biomass in the NAP region. Plain Language Summary: The sea around the northern Antarctic Peninsula (NAP) is known for its high productivity. According to in situ measurements and satellite observations, phytoplankton biomass in the NAP was anomalously high in summer 2006, as indicated by the surface concentrations of chlorophyll‐a being 2–3 times greater than the average. These high chlorophyll‐a anomalies were related to the westward shift of the Amundsen Sea Low, a climatological low‐pressure center that exerts great influence on the West Antarctica climate. The resulting positive pressure anomalies west of the NAP modulated the cloud cover and light over the study region by affecting the wind field and humidity. The increased light and the strengthened stratification generated this summer 2006 phytoplankton bloom. Key Points: Anomalous elevated chlorophyll‐a concentrations occurred in the northern Antarctic Peninsula region in summer 2006The combination of strong stratification and enhanced irradiance availability stimulated phytoplankton growth and accumulationStronger stratification and irradiance were caused by low cloudiness resulting from the dramatic westward shift of the Amundsen Sea Low [ABSTRACT FROM AUTHOR]
ISSN:21699275
DOI:10.1029/2024JC021354