C43E-06
The role of meltwater variability in modulating diurnal to inter-annual ice-sheet flow: New insights from a ~decade of high-temporal resolution GPS observations on the western Greenland margin
Thursday, 17 December 2015: 14:55
3002 (Moscone West)
Laura A Stevens1, Mark D Behn2, Sarah B Das3, Ian Joughin4, Michiel van den Broeke5, Thomas Herring1 and Jeffrey Joseph McGuire6, (1)Massachusetts Institute of Technology, Cambridge, MA, United States, (2)Woods Hole Oceanographic Institution, Geology and Geophysics, Woods Hole, MA, United States, (3)WHOI, Woods Hole, MA, United States, (4)Applied Physics Laboratory University of Washington, Seattle, WA, United States, (5)University of Oregon, Eugene, OR, United States, (6)Woods Hole Oceanographic Ins, Geology and Geophysics, Woods Hole, MA, United States
Abstract:
Meltwater-driven processes across the ablation zone of the Greenland Ice Sheet are controlled by seasonal fluxes as well as shorter-term variability in surface melt. Few high-temporal resolution GPS observations of ice-sheet flow extend for longer than a couple years, limiting multiyear analyses of seasonal variability in ice-sheet flow. Using a small GPS network installed at ~1000-m above sea level (m a.s.l.) operating from 2006–2014, and supplemented with a larger array of 20 GPS stations installed from 2011–2014, we observe nine years of ice-sheet surface motion on the western margin of the Greenland Ice Sheet. The GPS array spans a horizontal distance of 30 km across an elevation range of 700–1250 m a.s.l., and captures the ice-sheet’s velocity response to the seasonal melt cycle. By combining the GPS array measurements with temperature, precipitation, and runoff estimates from the Regional Atmospheric Climate Model (RACMO), we examine the relationship between ice-sheet flow and surface melt variability both at the seasonal scale (i.e., during melt onset, summer melt season and melt cessation) as well as during transient high melt periods such as precipitation events, anomalously high melt episodes, and supraglacial lake drainages. We observe varying surface motion following early versus late summer extended melt events, with early-season extended melt events inducing longer sustained speed-up than late summer events. We also examine differences in the timing of melt onset and magnitude, comparing the anomalously high runoff observed across the ice sheet in 2010 and 2012 against the average to low runoff observed in the years comprising the remainder of the record. This nearly decadal record improves our understanding of the role of meltwater variability in modulating ice-sheet flow on diurnal to inter-annual timescales.
