Impacts of Basal Melting of the Totten Ice Shelf and Biological Productivity on Marine Biogeochemical Components in Sabrina Coast, East Antarctica

To clarify the impacts of basal melting of the Antarctic ice sheet and biological productivity on biogeochemical processes in Antarctic coastal waters, concentrations of dissolved inorganic carbon (DIC), total alkalinity (TA), inorganic nutrients, chlorophyll a , and stable oxygen isotopic ratios (δ 18 O) were measured from the offshore slope to the ice front of the Totten Ice Shelf (TIS) during the spring/summer of 2018, 2019, and 2020. Modified Circumpolar Deep Water (mCDW) intruded onto the continental shelf off the TIS and flowed along bathymetric troughs into the TIS cavity, where it formed a buoyant mixture with glacial meltwater from the ice shelf base. Physical oceanographic processes mostly determined the distributions of DIC, TA, and nutrient concentrations. However, photosynthesis and dilution by meltwater from sea ice and the ice shelf base decreased DIC, TA, and nutrient concentrations in surface water near the ice front. These causes also reduced the partial pressure of CO 2 (pCO 2 ) in surface water by more than 100 μatm with respect to mCDW in austral summer of 2018 and 2020, and the surface water became a strong CO 2 sink for the atmosphere. Phytoplankton photosynthesis changed DIC and TA in a molar ratio of 106:16. Thus, pCO 2 decreased mostly as a result of photosynthesis while dilution by glacial and sea ice meltwater had a small effect. The nutrient consumption ratio suggested that photosynthesis was stimulated by iron in the water column, supplied to the surface layer via buoyancy‐driven upwelling and basal ice shelf meltwater in addition to sea ice meltwater. Oceanographic observations were made from the offshore continental slope to the Totten Ice Shelf (TIS) front in Sabrina Coast, East Antarctica, during spring/summer 2018, 2019, and 2020. Results revealed that surface water was strongly influenced by phytoplankton activity and the dilution effect of meltwater from sea ice and the base of the ice shelf. The nutrient consumption ratio between the winter water near the ice shelf front and surface water suggested that enough iron was present in the water column to stimulate photosynthesis. The iron was likely introduced into the surface water by buoyancy‐driven upwelling and meltwater from the base of the TIS in addition to sea ice meltwater. The inflow of modified Circumpolar Deep Water supplied biogeochemical components under the Totten Ice Shelf Surface water was influenced by dilution from ice shelf basal meltwater and sea ice m