North American ice sheet persistence during past warm periods should inform future projections

Roger Cameron Creel , Robert Kopp , Andrea Dutton, Maureen Raymo, Catherine Britt, Robert Deconto

How fast sea level rises in the next century will depend on how fast the Antarctic Ice Sheet responds to warming. Projections of future Antarctic Ice Sheet behavior are shaped by the assumption that peak sea level during past warm periods occurred after ice sheets had disappeared from North America. Here we present emerging evidence from paleoceanography and allied disciplines to argue that North American ice sheets endured well into some of the warmest interglacials of the last million years. We begin by reviewing the evidence for North American ice sheets persistence during past warm periods. We then show that overlooking this feature of past interglacials may lead projections of future ice sheet mass loss to systematically underestimate Antarctic Ice Sheet sensitivity to future warming. Finally, we propose that this paradigm shift opens avenues for future research that will increase confidence in the accuracy of climate and sea level projections.