Mid-Holocene Rapid Sea-Level Rise: A Window into the Future?

Existing records consistently show that global sea level started to rise progressively from 19000 cal BP and approached its present position by about 7000 cal BP due to the decay of major continental ice sheets in the Northern Hemisphere. Superimposed upon this general trend are episodic jumps of sea level, usually referred to as global meltwater pulses associated with abrupt collapses of portions of ice sheets at about 19000, 14200, and 11300 cal BP. However, little is known about the variability of sea level during the final stage of the last deglaciation. Two abrupt sea level rise events have been reported for about 8200 and 7600 cal BP, respectively. The former is commonly known as the “8.2 ka” event, likely related to the final outburst of the ice-dammed proglacial Lake Agassiz-Ojibway complex through the Hudson Strait. The predicted oceanic response to this massive freshwater release event is a eustatic sea-level fall in the near-field and a rise in the far-field, with an average eustatic sea-level rise of ~0.4 m. The event around 7600 cal BP remains controversial. Recent work in southeastern Scandinavia lends support to the abrupt nature of sea-level rise at this time. However, uncertainties still persist For example, recent high-resolution sea-level records from the Gulf of Mexico suggest that any such event had an amplitude of a meter or less. As this tandem of rapid sea level rise events occurred under climate boundary conditions broadly similar to the present, determining its magnitude, rate, and pattern may provide clues about the behavior of future sea level in response to the potential melting of polar ice sheets within the context of anthropogenic global warming. We conclude that the understanding of abrupt sea-level rise events during the early Holocene is still in its infancy.