Understanding Glacial Inception in Northeast Canada With a High-Resolution Regional Climate Model
Birch, Leah Michelle
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CitationBirch, Leah Michelle. 2018. Understanding Glacial Inception in Northeast Canada With a High-Resolution Regional Climate Model. Doctoral dissertation, Harvard University, Graduate School of Arts & Sciences.
AbstractOver the past 0.8 million years, 100 kyr ice ages have dominated Earth's climate. Interglacials were brief, sometimes lasting only a few thousand years. Currently, state-of-the-art global climate models (GCMs) have difficulty simulating glacial inception, due in part to their coarse horizontal resolution and neglect of ice flow dynamics. In this thesis, I address the inception problem using a high-resolution regional atmospheric model and an ice flow model. I explore three stages and corresponding mechanisms for glacial inception: mountain glacier growth, downslope ice flow from these mountain glaciers, and the atmospheric circulation response to ice sheet growth.
I use the Weather Research and Forecasting model (WRF), a cloud-resolving atmospheric model capable of a realistic simulation of the regional mountain climate and therefore of surface mass balance. I focus this study on the mountain glaciers of Canada's Baffin Island, where geologic evidence indicates the last inception occurred at 115 kya. I examine the sensitivity of mountain glaciers to insolation (Milankovitch forcing), topography, and meteorology, all part of the first stage of glacial inception. In addition, I investigate the radiative effects of clouds which are resolved by WRF rather than being parameterized.
I also examine the possible role of ice flow dynamics missing in GCMs and the interaction of expanding ice cover and the atmosphere. Using the WRF-derived mountain glacier mass balance, I run the ice sheet model based on the shallow-ice approximation, capturing the ice flow that may be critical to the spread of ice sheets away from mountain ice caps. The new ice surface elevation and extent are used as inputs in WRF. Through this iterated asynchronous coupling, I investigate how the regional climate and large-scale ciruclaiton respond to ice sheet changes, which are involved in the second and third stages of inception.
I find that ice would accumulate on mountain glaciers with anomalously cold meteorology, 115 kya, insolation, and realistic topography. Ice then proceeds to flow downslope, expanding the size the ice caps. However, the changing surface elevation induces an atmospheric response that warms the inception site, causing ice sheet growth to stagnate in the model, and therefore preventing full inception from occurring.
Citable link to this pagehttp://nrs.harvard.edu/urn-3:HUL.InstRepos:42015313
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