Excess ice loads prior to the Last Glacial Maximum in the Indian Ocean sector of East Antarctica derived from sea-level observations and GIA modeling

Further understanding of Antarctic Ice Sheet responses to global climate changes requires an accurate and continuous reconstruction of the AIS changes. However, the erosive nature of ice-sheet expansion and sea-level drop and the difficulty of accessing much of Antarctica make it difficult to obtain field-based evidence of ice-sheet and sea-level changes before the Last Glacial Maximum. Limited sedimentary records from the Indian Ocean sector of East Antarctica demonstrate that the sea level of Marine Isotope Stage 3 was close to the present level despite the global sea-level drop lower than −40 m. Although previous GIA-derived sea levels hardly explain these sea-level observations, we demonstrate glacial isostatic adjustment modeling with refined Antarctic Ice Sheet loading histories. Our experiments reveal that the Indian Ocean sector of the Antarctic Ice Sheet would have been required to experience excess ice loads before the Last Glacial Maximum in order to explain the observed sea-level highstands during Marine Isotope Stage 3. We also conduct a sensitivity test of the small Northern American Ice Sheet during Marine Isotope Stage 3, suggesting that this small ice sheet is not enough to achieve sea-level highstands during Marine Isotope Stage 3 in the Indian Ocean sector of East Antarctica. As such, we suggest that the Indian Ocean sector of the East Antarctic Ice Sheet reached its maximum thickness before the global Last Glacial Maximum.

 

Reference

Ishiwa, T., Okuno, J., and Suganuma, Y., 2021. Excess ice loads in the Indian Ocean sector of East Antarctica during the last glacial period. Geology, 49, 1182–1186. https://doi.org/10.1130/g48830.1