Transient rheology in sea level change: Implications for Meltwater Pulse 1A

Abstract

Ice mass and sea-level changes occur at many timescales inducing glacial isostatic adjustment (GIA). Typically, the solid Earth is treated as a Maxwell viscoelastic solid when predicting GIA at timescales from the peak of the ice age to present day (∼21,000 yr before present). For events occurring at shorter (daily-centennial) timescales, the solid Earth is often treated as an elastic solid. Experimental results within the rock mechanics community indicate that transient deformation occurs at intermediate timescales, neither captured by a Maxwell or elastic mechanical model. With realistic, experimentally constrained viscoelastic models, we explore transient deformation in short-, intermediate-, and long-term GIA measurements, then turn to Meltwater Pulse 1A (MWP-1A). MWP-1A occurred ∼14,500 yr ago and represents an event during which global mean sea level rose by ∼ 20 m within a timespan of, at most, 500 yr. With newly computed transient deformation, sea-level change predictions deviate substationally (∼1–2 m) from the Maxwell model at classic locations (Barbados, Sunda Shelf, Tahiti) that record MWP-1A sea level. These records are used to constrain the melt source of MWP-1A with important implications on ice sheet stability and the climate of a warming Earth. Our results suggest a timely need to revisit the source of MWP-1A and other analogous events.