Seasonal speedup of a Greenland marine-terminating outlet glacier forced by surface melt-induced changes in subglacial hydrology

• Published in: Journal of Geophysical Research
• Main Authors: Sole, AJ, Mair, DWF, Nienow, PW, Bartholomew, ID, King, MA, Burke, MJ, Joughin, I
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Geophysical Union 2011
• Subjects: Engineering; Geomatic Engineering; Geodesy; Greenland; glacier
• Online Access: https://doi.org/10.1029/2010JF001948; http://ecite.utas.edu.au/89661

We present subdaily ice flow measurements at four GPS sites between 36 and 72 kmfrom the margin of a marine‐terminating Greenland outlet glacier spanning the 2009melt season. Our data show that >35 km from the margin, seasonal and shortertimescale ice flow variations are controlled by surface meltinduced changes in subglacialhydrology. Following the onset of melting at each site, ice motion increased abovebackground for up to 2 months with resultant up‐glacier migration of both the onset andpeak of acceleration. Later in our survey, ice flow at all sites decreased to belowbackground. Multiple 1 to 15 day speedups increased ice motion by up to 40% abovebackground. These events were typically accompanied by uplift and coincided withenhanced surface melt or lake drainage. Our results indicate that the subglacial drainagesystem evolved through the season with efficient drainage extending to at least 48 kminland during the melt season. While we can explain our observations with reference toevolution of the glacier drainage system, the net effect of the summer speed variations onannual motion is small (∼1%). This, in part, is because the speedups are compensated forby slowdowns beneath background associated with the establishment of an efficientsubglacial drainage system. In addition, the speedups are less pronounced in comparison toland‐terminating systems. Our results reveal similarities between the inland ice flowresponse of Greenland marine‐ and land‐terminating outlet glaciers.