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 cracks in our understanding of the coupled ice, earth, and climate system. The last 130,000 year history of ice and climate change offers major changes in the state of the climate system as well as examples of abrupt tipping point behaviour. The dynamical source of the variability of this system is still poorly understood. There are also perplexing shortfalls in explaining inferred global mean sea level at Last Glacial Maximum (the problem of “missing ice”) as well the source of an inferred 6-10 m higher sea level during the last (Eemian) interglacial, about 125,000 years ago. Scientific assessments of potential climate change rely heavily on climate models. Though replication of present-day climate is a challenging test for models, it is only a limited test since these models are already tuned 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 associated meltwater drainage into the ocean. The proposed research will significantly refine these inferences through statistically robust integration of advanced computed models and large diverse sets of paleo data. This will either resolve or further clarify the missing ice issue. The research program will also apply these refined ice chronologies to direct examination of variability in the glacial ice and climate system with models encompassing the climate, ice sheet, and earth components. By deploying increasingly sophisticated models within this framework, we will test the extent to which current 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 evolution and associated ice sheet interactions with the climate system, addressing a major gap in current climate change assessments.