Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise.

Lauren J Gregoire,Ruza Ivanovic,Bette Otto‐Bliesner,Paul J Valdes

doi:10.1002/2016gl070356

Abstract

Elucidating the source(s) of Meltwater Pulse 1a, the largest rapid sea level rise caused by ice melt (14–18 m in less than 340 years, 14,600 years ago), is important for understanding mechanisms of rapid ice melt and the links with abrupt climate change. Here we quantify how much and by what mechanisms the North American ice sheet could have contributed to Meltwater Pulse 1a, by driving an ice sheet model with two transient climate simulations of the last 21,000 years. Ice sheet perturbed physics ensembles were run to account for model uncertainties, constraining ice extent and volume with reconstructions of 21,000 years ago to present. We determine that the North American ice sheet produced 3–4 m global mean sea level rise in 340 years due to the abrupt Bølling warming, but this response is amplified to 5–6 m when it triggers the ice sheet saddle collapse.

Highlights

Since the Last Glacial Maximum (LGM) around 23–21 thousand years ago, the Earth underwent a major transition into the current interglacial period, during which the North American and Eurasian continents deglaciated entirely, and the Greenland and Antarctic ice sheets, as well as glaciers worldwide, retreated
We determine that the North American ice sheet produced 3–4 m global mean sea level rise in 340 years due to the abrupt Bølling warming, but this response is amplified to 5–6 m when it triggers the ice sheet saddle collapse
Our results suggest that the North American ice sheet could have contributed to Meltwater Pulse 1a (MWP1a) through two different mechanisms: the ice saddle collapse caused by the separation of the Cordilleran and Laurentide ice sheets, which we associate with the timing of MWP1a, and accelerated melt from the abrupt Bølling warming in the Northern Hemisphere at 14.6 ka

Summary

Introduction

Since the Last Glacial Maximum (LGM) around 23–21 thousand years ago (ka), the Earth underwent a major transition into the current interglacial period, during which the North American and Eurasian continents deglaciated entirely, and the Greenland and Antarctic ice sheets, as well as glaciers worldwide, retreated. This produced around 130 m of global mean sea level rise (GMSLR) [Lambeck et al, 2014], which was sometimes contributed to by major episodes of accelerated ice melt. It is important to know how much the respective ice sheets each contributed to the event

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Conclusion