The phase space of last glacial inception:characterization and feedbacks via ensemble coupled ice/climate modelling

Bahadory, Taimaz (2019) The phase space of last glacial inception:characterization and feedbacks via ensemble coupled ice/climate modelling. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The feedbacks between ice sheets and the rest of the climate system are a major source of uncertainty in constraining future sea level change and perhaps aspects of future climate change. In the past, there is strong evidence that large and at times relatively abrupt changes in sea level and climate occurred. The past therefore offers a testable window that may help build confidence in projecting future changes. Climate models are used to study the evolution of ice and climate during glacial intervals. However, these models are either computationally expensive to run for glacial-scale periods, or are too simplified and miss key feedbacks between ice and the climate. To confidently model changes in the past, ensembles of transient model run on order 10 ky or longer are required. Therefore, a fast coupled ice-climate model with relevant feedbacks is required. Beyond last glacial maximum and especially beyond the range of accurate ¹⁴C dating (about 40-50 ka), constraints on past ice sheet evolution become sparse. The last glacial inception (herein including post inception peak retreat, thus covering the range of about 120 ka to 105 ka) is a poorly understood interval that includes both rapid ice sheet growth and subsequent decay. It thereby offers a challenging test for fully coupled ice and climate models. This thesis documents 3 specific contributions. 1) The fast fully coupled ice-climate model LCice 1.0 is documented. 2) Results from an ensemble of coupled transient simulations of the last glacial inception are presented. The ensemble provides a potential phase-space of ice and climate evolution during the last glacial inception. 3) Finally, multiple sensitivity experiments isolate the impacts of the two largest northern hemisphere ice sheets on climate and each other.

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