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Author ORCID Identifier

https://orcid.org/0000-0003-1959-5959

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Geosciences

Year Degree Awarded

2019

Month Degree Awarded

September

First Advisor

Alan Condron

Second Advisor

Ray Bradley

Subject Categories

Climate | Fresh Water Studies | Meteorology | Oceanography | Other Oceanography and Atmospheric Sciences and Meteorology

Abstract

Periods of abrupt climate cooling during the last deglaciation (20,000-8,000 yrs ago) are often attributed to glacial outburst floods slowing the Atlantic meridional overturning circulation (AMOC). Yet, despite over 40 years of research, conclusive evidence that such events significantly impact climate remains elusive. This study uses a climate model to investigate an alternative freshwater forcing mechanism in which the episodic break-up and mobilization of thick perennial Arctic sea ice might have disrupted large-scale climate. The results presented here show the first evidence that (1) the Arctic Ocean stored enormous volumes of freshwater during colder periods as thick masses of sea ice, and (2) that massive sea ice export events to the North Atlantic are generated whenever the transport of sea ice is enhanced either by changes in atmospheric circulation, rising sea level submerging the Bering land bridge, or glacial outburst floods draining into the Arctic Ocean from the Mackenzie River. Of relevance for understanding the key drivers of past abrupt climate change, I found that the volumes of freshwater released to the Nordic Seas are similar to, or larger than, those estimated to have come from terrestrial outburst floods, including a discharge around 12,900 years ago that is often considered the cause of the Younger Dryas cooling. The results from my thesis thus provide the first evidence that the storage and release of Arctic sea ice helped modulate deglacial climate change.

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