| Summary: | Studies of past glacial cycles yield critical information about climate and sea-level (ice-volume) variability,including the sensitivity of climate to radiative change, and impacts of crustal rebound on sealevelreconstructions for past interglacials. Here we identify significant differences between the lastand penultimate glacial maxima (LGM and PGM) in terms of global volume and distribution of land ice,despite similar temperatures and radiative forcing. Our analysis challenges conventional views of relationshipsbetween global ice volume, sea level, seawater oxygen isotope values, and deep-sea temperature,and supports the potential presence of large floating Arctic ice shelves during the PGM. Theexistence of different glacial ‘modes’ calls for focussed research on the complex processes behind ice-agedevelopment. We present a glacioisostatic assessment to demonstrate how a different PGM ice-sheetconfiguration might affect sea-level estimates for the last interglacial. Results suggest that this mayalter existing last interglacial sea-level estimates, which often use an LGM-like ice configuration, byseveral metres (likely upward).
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