Firn Stratigraphy and Temperature to 10 m Depth in the Percolation Zone of West Greenland, 2007-2009
INSTAAR Occasional Paper 60
2011, 25 pp. + CD. (cost: $13)
We present data from a field campaign focused on meltwater infiltration and horizontal water transport processes in firn of western Greenland. Data were collected during 2007-2009 along a 90 km transect extending from 2000 to 1300 m elevation. Fifteen intensive study sites were spaced 5-10 km along the transect. Near-surface heat flow was measured at each site with 33 channel thermistor strings extending to 10 m depth and logging year-round on a 30 minute time base. Firn stratigraphy and density were measured in 10-m-deep ice cores, with two or more cores at each study site for a total of 34 cores.
Analysis and interpretation of these data are made in other publications. Those analyses show that from 2000 to 1625 m elevation surface melt is minimal and meltwater infiltrates vertically to form thin ice layers. Between ≈1625 and 1475 m elevation strong surface melt infiltrates to fill about half of the available pore space of the upper 10 m. Infiltration shows a high degree of spatial variability in this elevation zone, with some water moving vertically and some water moving horizontally on top of decimeter- to meter-thick ice layers of irregular extent. In places, meltwater infiltrates to more than 10 m depth, and through multi-decade-old firn (i.e., well below the previous year's accumulation). Below ≈1475 m elevation, nearly all pore space is filled by infiltrated meltwater and excess water runs off. Both our thermal and density measurements indicate that the runoff limit is above the equilibrium line by on the order of 300 m in elevation and a distance of 30 km. Our results have implications for understanding the mass balance and surface elevation changes of the Greenland Ice Sheet.PDF (2 MB) | Core Data (22 KB) | Temp Data (6 MB)