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Sea ice, which forms in polar and nonpolar areas, transmits light to ice-associated (sympagic) algal communities. To noninvasively study the distribution of sea-ice algae, empirical relations to estimate its biomass from under-ice hyperspectral irradiance have been developed in the Arctic and Antarctica but lack for nonpolar regions. This study examines relationships between normalised difference indices (NDI) calculated from hyperspectral transmittance and sympagic algal biomass in the nonpolar Saroma-ko Lagoon. We analysed physico-biogeochemical properties of snow and land-fast sea ice supporting 27 paired bio-optical measurements along three transects covering an area of over 250 m × 250 m in February 2019. Snow depth (0.08 ± 0.01 m) and ice-bottom brine volume fraction (0.21 ± 0.02) showed low (0.06) and high (0.58) correlations with sea-ice core bottom section chlorophyll a (Chl. a), respectively. Spatial analyses unveiled the patch size of sea-ice Chl. a to be ~65 m, which is in the same range reported from previous studies. A selected NDI (669, 596 nm) explained 63% of algal biomass variability. This reflects the bio-optical properties and environmental conditions of the lagoon that favour the wavelength pair in the orange/red part of the spectrum and suggests the necessity of a specific bio-optical relationship for Saroma-ko Lagoon.

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 (δ18O) 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 CO2 partial pressure 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 CO2 sink for the atmosphere. Phytoplankton photosynthesis changed DIC and TA in a molar ratio of 106:16. Thus, CO2 partial pressure 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.

To clarify the impact 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. Off the TIS, modified Circumpolar Deep Water (mCDW) intruded onto the continental shelf and flowed along bathymetric troughs into the TIS cavity, where it met the ice shelf base and formed a buoyant mixture with glacial meltwater. Physical oceanographic processes mostly determined the distributions of DIC, TA, and nutrient concentrations. However, DIC, TA, and nutrient concentrations on the surface of the ice front were decreased by photosynthesis and the dilution effect of meltwater from sea ice and the base of the ice shelf. The partial pressure of CO 2 (pCO 2 ) in surface water was reduced by photosynthesis and dilution, and the surface water became a strong CO 2 sink for the atmosphere. The DIC and TA (normalized to salinity of 34.3 to correct for dilution effects) changed in a molar ratio of 106:16 because of phytoplankton photosynthesis. The decrease of pCO 2 by more than 100 μatm with respect to mCDW was thus the result of photosynthesis. The nutrient consumption ratio suggested that enough iron was present in the water column to supply the surface layer via buoyancy-driven upwelling and basal melting of the TIS. Hosted filetable1.docx available at https://authorea.com/users/534203/articles/598413-impacts-of-basalmelting-of-the-totten-ice-shelf-and-biological-productivity-on-marine-biogeochemicalcomponents-in-sabrina-coast-east-antarctica Hosted file support infomation tamura p et al.docx