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During the most recent deglaciation, the upwards trend of warmer Northern Hemisphere (NH) temperatures was punctuated by a rapid and intense return to glacial conditions: the Younger Dryas (YD). The end of this event marks the beginning of the Holocene. Using the University of Toronto version of CCSM4, a model of the climate prior to the YD was created with correct boundary conditions. Various amounts of freshwater forcing were then applied to the Beaufort Gyre for forcing intervals ranging from 1 to 125 years. In several cases, this was sufficient to collapse the Atlantic Meridional Overturning Circulation (AMOC) and cause significant cooling over the NH. Crucially, after the forcing was ceased, the AMOC stayed in an off state for approximately a millennium before mounting a rapid recover to pre-YD levels. This recovery, which permanently reduced the extent of NH sea ice, occurred through the mechanism of a Polynya opening in the Irminger Sea during winter and led to a pronounced “overshoot” of the AMOC, during which NH temperatures were higher than before the YD.

The ocean floor sedimentological signature of Heinrich event 3 (H3) is markedly different from that of other Heinrich events that are known to have originated in Hudson Strait. It has therefore been suggested that the H3 contribution to iceberg flux may have been delivered by ice streams located in the eastern sector of the North Atlantic, from the Fennoscandian or British Isles ice sheets. To investigate this possibility and whether the instability involved may have been tidally induced, as seems to have been the case for H1, we consider several eastern Atlantic sector possibilities: a hypothetical Barents Sea ice stream, the Norwegian ice stream, and the Irish Sea ice stream. We find that the extremely high amplitude of the M2 tidal constituent in the western North Atlantic that appears to have forced H1 did not exist in the northeastern Atlantic. This suggests that, with one possible exception, if destabilized ice streams in this region did contribute to H3, tidal forcing was most probably not the cause. The single exception to this general conclusion may be the Irish Sea ice stream, and we comment on the probability of a contribution to H3 from this source.

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.

We derive a general set of acceptable junction conditions for \\(F(T)\\) gravity via the variational principle. The analysis is valid for both the traditional form of \\(F(T)\\) gravity theory as well as the more recently introduced Lorentz covariant theory of Krššák and Saridakis. We find that the general junction conditions derived, when applied to simple cases such as highly symmetric static or time dependent geometries (such as spherical symmetry) imply both the Synge junction conditions as well as the Israel-Sen-Lanczos-Darmois junction conditions of General Relativity. In more complicated scenarios the junction conditions derived do not generally imply the well-known junction conditions of General Relativity. However, the junctions conditions of de la Cruz-Dombriz, Dunsby, and Sáez-Gómez make up an interesting subset of this more general case.