RESOLVING THE PEAK LAST INTERGLACIAL SEA-LEVEL BUDGET

The peak climate state of the last interglaciation (LIG; ~125 ka) was the last time global-mean sea level (GMSL) was significantly higher than present under a temperature forcing not drastically different from present. As of 8-10 years ago, peak LIG GMSL was estimated at +4-6 m, with the majority of the sea-level rise sourced from Greenland ice-sheet retreat. Most of these GMSL and Greenland ice-volume estimates neglected impacts of glacial isostatic adjustment or did not match existing ice-core records, respectively. In the last decade, the timing, magnitude and sources of sea-level rise during the LIG has been investigated as part of the PALSEA2 INQUA-PAGES working group, which brings field sea-level and ice-sheet scientists, and geophysical ice-sheet, climate and mantle modelers together around a common paleo ice-sheet/sea-level theme. Based on this trans-disciplinary, international effort, a consistent picture of the LIG sea-level budget is emerging. LIG GMSL is now estimated to have peaked at +6-9 m after accounting for the impact of glacial isostatic adjustment on sea-level indicators. Marine and ice-core records of LIG Greenland ice-sheet extent show that while the ice sheet was smaller than present, ice persisted largely intact on much of the island. Newer ice-sheet models with improved climate forcing agree with these insights, and place the Greenland GMSL contribution at +0.6-3.5 m. Given revised LIG GMSL, Antarctic ice sheets must have contributed a significant portion of the higher GMSL, despite the current lack of field-based evidence from Antarctica. Remaining debates include the existence and magnitude of possible GMSL oscillations during the LIG, the source(s) of such oscillations, and the timing of peak GMSL.