Interannual and spatial variation in small zooplankton off Vincennes Bay, East Antarctica

Tachibana, Aiko; Ohkubo, Yusaku; Matsuno, Kohei; Takahashi, Keigo D.; Makabe, Ryosuke; Moteki, Masato

doi:10.1007/s00300-023-03174-0

Cited by 3 publications

(3 citation statements)

References 55 publications

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“…While part of the high chlorophyll‐ a concentration near the sea ice edge might result from sub‐ice blooms, these blooms would be enhanced or sustained by the strong near‐surface stratification there established by concentrated sea ice meltwater, which is consistent with our argument. The inhomogeneous distribution of phytoplankton growth might also shape the spatial distribution of zooplankton and higher trophic levels (e.g., Tachibana et al., 2023). In addition, the spatially concentrated distribution of ice shelf basal meltwater has a potential influence on the nutrient availability and cycling in the region, as the ice shelf basal meltwater is rich in iron, a major limiting factor for the phytoplankton growth in the region (Dinniman et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

Influence of Physical Factors on Restratification of the Upper Water Column in Antarctic Coastal Polynyas

Xu,

Zhang,

Maksym

et al. 2024

JGR Oceans

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Antarctic coastal polynyas are hotspots of biological production with intensive springtime phytoplankton blooms that strongly depend on meltwater‐induced restratification in the upper part of the water column. However, the fundamental physics that determine spatial inhomogeneity of the spring restratification remain unclear. Here, we investigate how different meltwaters affect springtime restratification and thus phytoplankton bloom in Antarctic coastal polynyas. A high‐resolution coupled ice‐shelf/sea‐ice/ocean model is used to simulate an idealized coastal polynya similar to the Terra Nova Bay Polynya, Ross Sea, Antarctica. To evaluate the contribution of various meltwater sources, we conduct sensitivity simulations altering physical factors such as alongshore winds, ice shelf basal melt, and surface freshwater runoff. Our findings indicate that sea ice meltwater from offshore is the primary buoyancy source of polynya near‐surface restratification, particularly in the outer‐polynya region where chlorophyll concentration tends to be high. Downwelling‐favorable alongshore winds can direct offshore sea ice away and prevent sea ice meltwater from entering the polynya region. Although the ice shelf basal meltwater can ascend to the polynya surface, much of it is mixed vertically over the water column and confined horizontally to a narrow coastal region, and thus does not contribute significantly to the polynya near‐surface restratification. Surface runoff from ice shelf surface melt could contribute greatly to the polynya near‐surface restratification. Nearby ice tongues and headlands strongly influence the restratification through modifying polynya circulation and meltwater transport pathways. Results of this study can help explain observed spatiotemporal variability in restratification and associated biological productivity in Antarctic coastal polynyas.

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Section: Discussionmentioning

confidence: 99%

Influence of Physical Factors on Restratification of the Upper Water Column in Antarctic Coastal Polynyas

Xu,

Zhang,

Maksym

et al. 2024

JGR Oceans

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show abstract

“…While part of the high chlorophyll-a concentration near the sea ice edge might result from sub-ice blooms, these blooms would be enhanced or sustained by the strong near-surface stratification there established by concentrated sea ice meltwater, which is consistent with our argument. The inhomogeneous distribution of phytoplankton growth might also shape the spatial distribution of zooplankton and higher trophic levels (e.g., Tachibana et al, 2023). In addition, the spatially concentrated distribution of ice shelf basal meltwater has a potential influence on the nutrient availability and cycling in the region, as the ice shelf basal meltwater is rich in iron, a major limiting factor for the phytoplankton growth in the region (Dinniman et al, 2020).…”

Section: Implications On Biological Productivitymentioning

confidence: 99%

Influence of Physical Factors on Restratification of the Upper Water Column in Antarctic Coastal Polynyas

Xu,

Zhang,

Maksym

et al. 2023

Preprint

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Antarctic coastal polynyas are hotspots of biological production with intensive springtime phytoplankton blooms that strongly depend on meltwater-induced restratification in the upper part of the water column. However, the fundamental physics that determine spatial inhomogeneity of the spring restratification remain unclear. Here, we investigate how different meltwaters affecting springtime restratification and thus phytoplankton bloom in Antarctic coastal polynyas. A high-resolution coupled ice-shelf/sea-ice/ocean model is used to simulate an idealized coastal polynya similar to the Terra Nova Bay Polynya. To evaluate the contribution of various meltwater sources, we conduct sensitivity simulations that alter physical factors such as alongshore winds, ice shelf basal melt rates, and surface freshwater runoff. Our findings indicate that sea ice meltwater from offshore is the primary buoyancy source of polynya near-surface restratification, particularly in the outer-polynya region where chlorophyll concentration tends to be high. Downwelling-favorable alongshore winds can direct offshore sea ice away and prevent sea ice meltwater from entering the polynya region. Although the ice shelf basal meltwater can ascend to the polynya surface, much of it is mixed vertically over the water column and confined horizontally to a narrow coastal region, and thus does not contribute significantly to the polynya near-surface restratification. Surface runoff from ice shelf surface melt could contribute greatly to the polynya near-surface restratification. Nearby ice tongues and headlands strongly influence the restratification process through modifying polynya circulation and meltwater transport pathways. Results of this study can help explain observed spatiotemporal variability in restratification and associated biological productivity in Antarctic coastal polynyas.

show abstract

“…While part of the high chlorophylla concentration near the sea ice edge might result from sub-ice blooms, these blooms would be enhanced or sustained by the strong near-surface stratification there established by concentrated sea ice meltwater, which is consistent with our argument. The inhomogeneous distribution of phytoplankton growth might also shape the spatial distribution of zooplankton and higher trophic levels (e.g., Tachibana et al 2023). In addition, the spatially concentrated distribution of ice shelf basal meltwater has a potential influence on the nutrient availability and cycling in the region, as the ice shelf basal meltwater is rich in iron, a major limiting factor for the phytoplankton growth in the region (Dinniman et al 2020).…”

Section: Implications On Biological Productivitymentioning

confidence: 99%

Processes of stratification breakdown and restratification in Antarctic coastal polynyas

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Antarctic coastal polynyas are areas of persistent open water surrounded by sea ice. They are characterized by deep winter mixing due to dense water formation from sea ice production and elevated biological productivity after spring restratification. Antarctic coastal polynyas are diverse in terms of their mixing and stratification pattern, as well as the associated biological productivity. Here, we combine satellite and in situ observations, idealized numerical models, and analytical scaling to investigate the three-dimensional polynya circulation and explore the physical factors that control the winter destratification and springtime restratification in coastal polynyas. The highresolution coupled model with ice shelf, sea ice, and ocean components qualitatively reproduces the observed coastal polynyas and sea ice fields, as evidenced by satellite measurements. In winter, strong offshore ocean currents driven by offshore katabatic winds carry some newly-formed dense water away from the polynya, weakening the destratification rate in the polynya water column. In contrast, coastal easterly winds induce onshore Ekman transport, constrain dense water outflows, and intensify vertical mixing. Moreover, an ice tongue and coastline geometry can modify sea ice and ocean circulations, thus influencing the dense water dispersal pathways and destratification in polynyas. In spring, offshore-originating sea ice meltwater primarily drives polynya restratification in the top 100 m of the water column. Even though ice shelf basal meltwater can ascend to the polynya surface, much of it is mixed over the upper 100–200 m and does not have a significant contribution to the near-surface restratification. The surface runoff from the ice shelf surface melt could potentially contribute significantly to the near-surface restratification, but its magnitude is less constrained with high uncertainty. This thesis provides a framework to study mixing and stratification dynamics in Antarctic coastal polynyas. It helps to explain their associated variabilities in dense water formation and biological productivity.

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Interannual and spatial variation in small zooplankton off Vincennes Bay, East Antarctica

Cited by 3 publications

References 55 publications

Influence of Physical Factors on Restratification of the Upper Water Column in Antarctic Coastal Polynyas

Influence of Physical Factors on Restratification of the Upper Water Column in Antarctic Coastal Polynyas

Influence of Physical Factors on Restratification of the Upper Water Column in Antarctic Coastal Polynyas

Processes of stratification breakdown and restratification in Antarctic coastal polynyas

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