A near global distribution of regional deglacial meltwater and iceberg discharge chronologies from data-calibrated glaciological modelling

Abstract:

Freshwater fluxes from ice sheets are thought to have played a critical role in past glacial cycle climate evolution and variability. To facilitate clearer assessment of such interactions, a deglacial probabilistic distribution of regionally-disaggregated meltwater and iceberg discharge chronologies has been subject to ongoing development as part of the GLAC series of data-calibrated global ice sheet reconstructions. The North American (NA) and Eurasian (EA) components of GLAC are from full Bayesian calibrations of a 3D glacial systems model, while the Antarctic (ANT) component is from data-scoring of an initial 3344 member exploratory ensemble of model runs. Constraint data sets used for the calibration and data-scoring include: relative sea level (all), present-day vertical velocities (NA and EA), geologically-inferred deglacial ice margin chronologies (NA and EA), marine limits (NA),strandline constraints for pro-glacial lakes (NA), present-day ice thickness (ANT), and terrestrial and marine dates constraining past ice cover (ANT).

I will present the disaggregated distribution of discharge chronologies for the three ice sheets and critically compare them against past inferences. I will also discuss key uncertainties that have not yet been accounted for as well as ongoing efforts to reduce and/or otherwise account for those uncertainties. A key feature of GLAC that recent studies continue to ignore is that there can be significant simultaneous discharge from multiple drainage sectors of a given ice sheet. For instance, a robust feature of GLAC is a dominant Meltwater Pulse 1a contribution from multiple North American sectors.