Relating Atmospheric Circulation Patterns to Intense Surface Melt Periods along Coastal West Greenland

Supraglacial melt lakes have been found to be an important component to ice sheet hydrology as they have the propensity to drain large amounts (4.4 x 10⁷ m³) of water in a short amount of time (~2 hours), and with little predictability. Melt lake drainage events (hydrofracturing) triggers an increase in velocity at nearby outlet glaciers by lubrication at the ice-bedrock interface (Zwally Effect); this process further enhances the ice sheet's contribution to sea level rise. We seek to better understand the controls on melt lake growth by analyzing synoptic-scale atmospheric circulation (via Synoptic indexing) over western Greenland during the peak time of the ablation season (late June) during the 2000-2012 summers. We identify a relationship between the North Atlantic Oscillation (NAO) and melt lake areas, in that summers with highly negative NAO values (NAO-) correlate with high melt years. We suggest two mechanisms responsible for anomalous melt patterns in the ablation (or melt) zone in coastal west Greenland: 1) Melting resulting from in-situ solar radiative forcing and 2) Advection of relatively Warm Maritime Air (from the North Atlantic).