| Summary: | The ocean coastal-shelf-slope ecosystem west of the Antarctic Peninsula (WAP) is a
biologically productive region that could potentially act as a large sink of atmospheric carbon dioxide.
The duration of the sea-ice season in the WAP shows large interannual variability. However, quantifying
the mechanisms by which sea ice impacts biological productivity and surface dissolved inorganic carbon
(DIC) remains a challenge due to the lack of data early in the phytoplankton growth season. In this study,
we implemented a circulation, sea-ice, and biogeochemistry model (MITgcm-REcoM2) to study the
effect of sea ice on phytoplankton blooms and surface DIC. Results were compared with satellite seaice
and ocean color, and research ship surveys from the Palmer Long-Term Ecological Research (LTER)
program. The simulations suggest that the annual sea-ice cycle has an important role in the seasonal DIC
drawdown. In years of early sea-ice retreat, there is a longer growth season leading to larger seasonally
integrated net primary production (NPP). Part of the biological uptake of DIC by phytoplankton, however,
is counteracted by increased oceanic uptake of atmospheric CO2. Despite lower seasonal NPP, years of late
sea-ice retreat show larger DIC drawdown, attributed to lower air-sea CO2 fluxes and increased dilution
by sea-ice melt. The role of dissolved iron and iron limitation on WAP phytoplankton also remains a
challenge due to the lack of data. The model results suggest sediments and glacial meltwater are the main
sources in the coastal and shelf regions, with sediments being more influential in the northern coast.
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