Examining the glacial cycle phase space through data-integrated glacial systems modelling

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The past is our fuzzy window to the future. Through this window, tantalizing discrepancies point to cracksin our understanding of the coupled ice, earth, and climate system. The last 130,000 year history of ice andclimate change offers major changes in the state of the climate system as well as examples of abrupt tippingpoint behaviour.The dynamical source of the variability of this system is still poorly understood. There are also perplexingshortfalls in explaining inferred global mean sea level at Last Glacial Maximum (the problem of “missingice”) as well the source of an inferred 6-10 m higher sea level during the last (Eemian) interglacial, about125,000 years ago.Scientific assessments of potential climate change rely heavily on climate models. Though replication ofpresent-day climate is a challenging test for models, it is only a limited test since these models are alreadytuned to fit the present. To answer questions related to potentially large changes in the climate system(especially so-called tipping points), models are best tested against the past.Critical to these tests is a confident inference of the past change in topography, ice cover, and associatedmeltwater drainage into the ocean. The proposed research will significantly refine these inferences throughstatistically robust integration of advanced computed models and large diverse sets of paleo data. Thiswill either resolve or further clarify the missing ice issue. The research program will also apply theserefined ice chronologies to direct examination of variability in the glacial ice and climate system with modelsencompassing the climate, ice sheet, and earth components.By deploying increasingly sophisticated models within this framework, we will test the extent to whichcurrent models and understanding can replicate and explain past ice sheet evolution and instability events.These tests will in turn facilitate the estimation of uncertainties concerning both future ice sheet evolutionand associated ice sheet interactions with the climate system, addressing a major gap in current climatechange assessments.