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How fast future sea level rises will depend on the Antarctic Ice Sheet (AIS) response to warming. AIS projections are shaped by the assumption that sea-level peaks during past interglacials occurred after the North American ice sheet complex (NAIS) disappeared. We synthesize evidence from paleoceanography and allied disciplines to argue that NAIS persisted into some of the warmest interglacials of the last million years. We show that overlooking NAIS persistence may lead to underestimation of AIS sensitivity to warming, and propose that this paradigm shift opens research avenues that can increase confidence in the accuracy of climate and sea-level projections. 

Abstract An investigation of lake-effect (LE) and the associated synoptic environment is presented for days when all five lakes in the Great Lakes (GL) region had LE bands (5LD). The study utilized an expanded database of observed LE clouds over the GL during 25 cold seasons (October–March) from 1997/1998 to 2021/2022. LE bands occurred on 2870 days (64% of all cold-season days). Nearly a third of all LE bands occurred during 5LD, although 5LD consisted of just 17.1% of LE days. A majority of 5LD (56.5%) had L2L and these days comprised 43.5% of all L2L occurrences. 5LD occurred with a mean of 26.1 (SD=6.2) days per cold season until 2008/2009 and then decreased to a mean of 13.8 (SD=5.5) days during subsequent cold seasons. January and February had the largest number of consecutive LE days in the GL with a mean of 5.7 and 5.4 days, respectively. As the number of consecutive LE days increase, both the number of 5LD and the occurrence of consecutive 5LD increase. This translates to an increased potential of heavy snowfall impacts in multiple, localized areas of the GL for extended time periods. The mean composite synoptic pattern of 5LD exhibited characteristics consistent with lake-aggregate disturbances and showed similarity to synoptic patterns favorable for LE over one or two of the GL found by previous studies. The results demonstrate that several additional areas of the GL are often experiencing LE bands when a localized area has active LE bands occurring.