The Effect of Basal Melting of the Shirase Glacier Tongue on the CO2 System in Lutzow-Holm Bay, East Antarctica

To clarify the effect of basal melting of ice tongues/ice shelf on the CO2 system in the Antarctic continental margin, seawater samples were collected for analysis of dissolved inorganic carbon (DIC), total alkalinity (TA), nutrients, chlorophyll a (chl.a), and oxygen isotopic ratios at the ice front of the Shirase Glacier Tongue (SGT) in Lutzow-Holm Bay (LHB), East Antarctica during the summers of 2017 and 2018. At depths greater than similar to 20 dbar in LHB, CO2 system parameters were strongly influenced by the dilution effect of SGT basal melting and the inflow of modified Circumpolar Deep Water (mCDW). The distributions of DIC and TA agreed well with an offshore origin of mCDW that flowed beneath the SGT and mixing of basal meltwater and mCDW beneath the SGT. The fraction of SGT meltwater was highest at the station near the ice front. Dilution by SGT basal meltwater reduced the partial pressure of CO2 in the mCDW from 431 to 387 mu atm. The water then became a sink rather than source of atmospheric CO2. In the sea surface, DIC and TA were strongly influenced by biological processes. Salinity-normalized DIC decreased with the increase of salinity-normalized TA in accord with 106:16 C:N molar stoichiometry; the chl.a concentration at the sea surface was as high as 31 mu g L-1.

Automated summary

The study focused on the impact of basal melting of ice tongues/ice shelf on the CO2 system in the Antarctic continental margin by analyzing seawater samples collected at the ice front of the Shirase Glacier Tongue in East Antarctica. Results showed that the dilution effect of SGT basal melting and the inflow of modified Circumpolar Deep Water significantly influenced the CO2 system parameters in the area, reducing the partial pressure of CO2 in the modified Circumpolar Deep Water. Additionally, biological processes strongly affected DIC and TA at the sea surface, with a high concentration of chl.a observed.