Modeling the oxygen isotope composition of the Antarctic ice sheet and its significance to Pliocene sea leve

Recent estimates of global mean sea level based on the oxygen isotope composition of mid-Pliocene benthic foraminifera vary from 9 to 21 m above present, which has differing implications for the past stability of the Antarctic ice sheet during an interval with atmospheric CO2 comparable to present. Here we simulate the oxygen isotope composition of the Antarctic ice sheet for a range of configurations using isotope-enabled climate and ice sheet models. We identify which ice-sheet configurations are consistent with the oxygen isotope record and suggest a maximum contribution from Antarctica to the mid-Pliocene sea level highstand of ~13 m. We also highlight that the relationship between the oxygen isotope record and sea level is not constant when ice is lost from deep marine basins, which has important implications for the use of oxygen isotopes as a sea level proxy.