Temporal and Spatial Variation in Surface Velocity and Basal Friction at Upernavik Isstrøm, Northwest Greenland

Abstract:

Upernavik Isstrøm (UI) in Northwest Greenland consists of 4 main marine terminating outlets terminating into the same fjord (Upernavik Isfjord). The individual glaciers at UI have shown general acceleration in ice speed since 1985 (Khan et al., 2013), however, the spatial and temporal patterns of these events are highly variable. The different response to similar climate forcings of the 4 marine terminating outlet glaciers makes UI a good study site for understanding processes important for the highly complex relation between climate and dynamic mass loss. Basal friction is one of the major controls of ice flow and is poorly known due to the inaccessibility of the bed. Basal friction depends on the origin and temperature of the bed, ice flow velocity, as well as basal hydrology including surface meltwater reaching the bed. Knowledge about the evolution of the basal friction pattern will increase our understanding of the relation between climate and ice dynamics. In this study we use the velocity maps from the MEaSURES Ice Velocity dataset (Joughin et al., 2011) to investigate velocity changes at UI from 2000 – 2013. With a focus on the seasonal changes from 2009 to 2013 where maps are usually available for February, April, July, August and November. The study show how the acceleration event at the northernmost glacier in 2006-2007 (Khan et al., 2013), continues into 2010. Furthermore, we see a large acceleration from 2008 and onwards on the second glacier, increasing the accelerated area dramatically and causing thinning of more than 2 m/yr upstream glacier (~30 km from the margin). The velocity maps will be used to obtain basal friction maps by inverting the full stokes solution in the Ice Sheet System Model (ISSM) as in Morlighem et al. (2010) to investigate the evolution of the basal friction throughout the period.