Maffezzoni, L (2022) Extratropical Cyclones and their influence on Greenland Ice Sheet surface mass balance and dynamics. Doctoral thesis, Liverpool John Moores University.

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Abstract

The Greenland Ice Sheet (GrIS) stores enough freshwater to raise global sea level by more than 7 m, so its response to climate variability is of considerable societal significance. Extratropical cyclones impact its surface mass budget (SMB) via both solid and liquid precipitation but their impacts on surface energy balance (SEB) are less known. Moreover, the ability of cyclonic rainfall to reach and perturb the ice-bed interface influencing ice dynamics, remains an open question. The thesis helps fill these knowledge gaps by 1) exploring the net effect of extratropical cyclones on the GrIS surface mass balance; and 2) investigating how they can influence ice dynamics through their input of meltwater and rainfall to the subglacial hydrological system.
The first aim was addressed by calculating mean meteorological and surface mass/energy balance terms during periods when the GrIS was under the influence of extratropical cyclones. This was achieved using a 58-year integration of the Model Atmospherique Regional (MAR) along with a cyclone dataset covering the Northern Hemisphere for the same period. The results indicated that extratropical cyclones have a net positive effect on GrIS mass balance in summer, lowering air temperatures and increasing albedo (due to snowfall) that suppress the meltwater production in the ablation region. During winter, the analysis reveals abundant snowfall leading again to a positive impact on GrIS mass balance.
The MAR outputs and the cyclone dataset were also used to identify cyclonic rainfall events over the western flank of the GrIS during late summer/early autumn; the period where their occurrence could have the biggest impact on ice dynamics. A GIS procedure was applied to data from the GoLIVE and MEaSUREs Selected Glacier satellite ice velocity datasets to extract ice motion of the glaciers during the melt season and around the cyclonic period. The major finding here was an acceleration along both marine and land terminating glaciers in response to extratropical cyclone passage, forced by subglacial hydrological changes resulting from inputs of rainfall and meltwater. The thesis therefore concludes that extratropical cyclones have a positive impact on the net surface mass balance in the current climate, but that their passage during autumn may already enhance dynamic thinning.

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	Glaciers; Extratropical Cyclones; Greenland Ice Sheet; Global Warming; Climate Change
Subjects:	G Geography. Anthropology. Recreation > G Geography (General) G Geography. Anthropology. Recreation > GE Environmental Sciences
Divisions:	Biological & Environmental Sciences (from Sep 19)
SWORD Depositor:	A Symplectic
Date Deposited:	07 Nov 2022 17:10
Last Modified:	07 Nov 2022 17:11
DOI or ID number:	10.24377/LJMU.t.00018016
Supervisors:	Edwards, L and Matthews, T
URI:	https://researchonline.ljmu.ac.uk/id/eprint/18016

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