The role of the Eurasian Ice Sheet in meltwater pulse 1A (15-14 ka BP). Numerical studies.

The last deglaciation (21-0 ka BP) was punctuated by a sequence of abrupt changes in the climate system recorded in geological proxies. The eustatic sea level did not rise steadily but rather reflected the steps of deglaciation of the major ice sheets, showing accelerations and slowdowns. The period of largest sea-level acceleration, recorded in fossilized coral reefs, is known as Meltwater Pulse 1A (MWP-1A). Several hypotheses have been proposed on its origin but it still lacks a definitive answer, due to large uncertainties in geologic records and in paleoclimate modelling. The present study aims at constraining the contribution of the Eurasian ice sheet to the event, using a thermodynamical ice sheet--ice shelves model, forced by the pre-existing climate output from CCSM3 transient deglaciation experiment (TraCE-21ka), to run simulations of the Northern Hemisphere deglaciation. The simulation that best fit the global volume of the ICE-5G ice model, was used as initial conditions for further sensitivity tests. The isostatic response of the reference run and of those that trigger a MWP from Eurasia, has been computed by means of an Earth model solving the gravitationally self consistent sea level equation. Anomalies of rate of sea-level rise and vertical uplift can be used to constrain the "fingerprint" of the past collapse of a major ice sheet. The simulated isostatic response of Eurasia to MWP-1A yelds realistic fingerprints, suggesting that a contribution by this ice sheet to MWP-1A is a viable hypothesis. In our best fitting ice sheet simulation, Eurasia contributes 4.5 m Sea Level Equivalent to MWP-1A, with rates reaching 35.3 mm/yr, slightly lower than suggested by the proxies. Further tuning of both ice sheet and Earth models are needed to refine those results.