Dissertation

Tidally Forced Marine Ice Stream Instabilities and Their Consequences

Velay-Vitow, Jesse

2024

Overview

The dual time-scale nature of the 100-kyr glacial cycle involves a slow 90-kyr glaciation and a rapid 10-kyr deglaciation. Since its discovery in ice cores recovered from Greenland, the rapid deglaciation has proven mysterious. I present a novel explanation for this phenomenon, wherein the deglaciation of the Laurentide ice sheet is accelerated by the rapid collapse of marine-terminating ice streams. The collapse of these ice streams is forced by high-amplitude tides at the grounding line, and the process of glacioisostatic adjustment is responsible for creating the bathymetric and glaciological conditions required for these collapses. Three ice streams are investigated, which existed in the Hudson Strait, The Amundsen Gulf, and the Gulf of St. Lawrence.I additionally find that the recovery from the Younger Dryas occurred through the same mechanism as Dansgaard-Oeschger oscillations, specifically a polynya opening in the Irminger Sea allowing for the exchange of heat between the ocean and atmosphere and the resumption of the Atlantic Meridional Overturning Circulation (AMOC). The fingerprinting of the contributions from all major ice sheets for MWP1A and MWP1B is presented, and I propose the St. Lawrence River as the route by which MWP1B entered the ocean. This allows me to present both an updated model of ice loading history and an explanation for all major climatic events of the last 20,000 years in which the resumption of the AMOC after Heinrich event 1 leads to the Bølling-Allerød warming, which results in increased melt of the Laurentide and provides the source of MWP1A. Similarly, the recovery of the AMOC after the Younger Dryas leads to the pre-boreal oscillation which provides the source for MWP1B.

• Publisher: ProQuest Dissertations & Theses
• Subject: Climate Change / Computational physics / Geophysical engineering / Geophysics
• ISBN: 9798342740401