Presentation Arctic outlet glacier dynamics, debris cover and pro-glacial lakes

Marine-terminating outlet glaciers allow Arctic ice masses, such as the Greenland Ice Sheet, to respond very rapidly to climate change. Outlet glaciers can undergo kilometres of retreat in just a few years and changes at the glacier terminus can be transmitted far inland, resulting in acceleration and thinning of inland ice. At present, accelerated ice discharge from marine-terminating outlet glaciers accounts for one-third to one half of ice loss from Greenland and is a major mass loss mechanism on other Arctic ice caps. Consequently, understanding changes in the dynamics of marine-terminating outlet glaciers is vital for accurately forecasting future sea level rise. However, there are major uncertainties over the factors controlling their behaviour and about their response to climate change. My research focuses on these uncertainties and I use a combination of remote sensing, numerical modelling and fieldwork. I will present a selection of my recent results, in order to highlight important findings and key themes from my work. Assessment of outlet glacier retreat rates across the Arctic shows that they are behaving similarly at decadal timescales and are retreating at an accelerating rate. Of the 273 study glaciers, 97% retreated between 2000-2010, compared to just 74% between 1992-2000 and mean retreat rates increased from 30.5 ma-1 to 105.8 ma-1. Retreat correlates with strong reductions in sea ice concentrations, but there was very large variability in glacier retreat rates within regions and even between neighbouring glaciers. We attribute this to the shape of the glacier fjord, which strongly effects the rate at which individual glaciers retreat, and means that neighbouring glaciers may respond very differently to the same climate forcing, which makes prediction complicated. Focusing specifically on Novaya Zemlya, which is located in the Russian High Arctic and contains 24,000 km2 of ice, glacier retreat was particularly rapid between 2000 and 2013. However, retreat rates have now slowed, which contrasts with the rest of the Arctic. Northern Greenland is an important, but comparatively little-studied region. It covers approximately 40% of the Greenland Ice Sheet by area and a number of large, floating ice tongues in the region have recently collapsed. At Humboldt Glacier, northern Greenland, we show that basal topography can result in order of magnitude differences in retreat rate on the same glacier. This is very important for forecasting ice loss elsewhere, as many Greenland outlet glaciers are located in similar, deep troughs. Finally, fieldwork results show that debris cover is a very strong control on melt rates in central-west Greenland and this is predicted to become increasingly important, as climate warms and the ice sheet darkens.
Polar Meteorology and Glaciology Group seminar / 気水圏コロキウム 日時:9月5日(月)14:00-14:50 場所:C301(3階セミナー室)

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