TY - JOUR
T1 - Assessing the summer water budget of a moulin basin in the sermeq avannarleq ablation region, Greenland ice sheet
AU - McGrath, Daniel
AU - Colgan, William
AU - Steffen, Konrad
AU - Lauffenburger, Phillip
AU - Balog, James
PY - 2011/10
Y1 - 2011/10
N2 - We provide an assessment of the supraglacial water budget of a moulin basin on the western margin of the Greenland ice sheet for 15 days in August 2009. Meltwater production, the dominant input term to the 1.14 ± 0.06 km2 basin, was determined from in situ ablation measurements. The dominant water-output terms from the basin, accounting for 52% and 48% of output, respectively, were moulin discharge and drainage into crevasses. Moulin discharge exhibits large diurnal variability (0.017-0.54 m3 s-1) with a distinct late-afternoon peak at 16:45 local time. This lags peak meltwater production by ∼2.8 ± 4.2 hours. An Extreme Ice Survey time-lapse photography sequence complements the observations of moulin discharge. We infer, from in situ observations of moulin geometry, previously published borehole water heights and estimates of the temporal lag between meltwater production and observed local ice surface uplift ('jacking'), that the transfer of surface meltwater to the englacial water table via moulins is nearly instantaneous (<30min). We employ a simple crevasse mass-balance model to demonstrate that crevasse drainage could significantly dampen the surface meltwater fluctuations reaching the englacial system in comparison to moulin discharge. Thus, unlike crevasses, moulins propagate meltwater pulses to the englacial system that are capable of overwhelming subglacial transmission capacity, resulting in enhanced basal sliding.
AB - We provide an assessment of the supraglacial water budget of a moulin basin on the western margin of the Greenland ice sheet for 15 days in August 2009. Meltwater production, the dominant input term to the 1.14 ± 0.06 km2 basin, was determined from in situ ablation measurements. The dominant water-output terms from the basin, accounting for 52% and 48% of output, respectively, were moulin discharge and drainage into crevasses. Moulin discharge exhibits large diurnal variability (0.017-0.54 m3 s-1) with a distinct late-afternoon peak at 16:45 local time. This lags peak meltwater production by ∼2.8 ± 4.2 hours. An Extreme Ice Survey time-lapse photography sequence complements the observations of moulin discharge. We infer, from in situ observations of moulin geometry, previously published borehole water heights and estimates of the temporal lag between meltwater production and observed local ice surface uplift ('jacking'), that the transfer of surface meltwater to the englacial water table via moulins is nearly instantaneous (<30min). We employ a simple crevasse mass-balance model to demonstrate that crevasse drainage could significantly dampen the surface meltwater fluctuations reaching the englacial system in comparison to moulin discharge. Thus, unlike crevasses, moulins propagate meltwater pulses to the englacial system that are capable of overwhelming subglacial transmission capacity, resulting in enhanced basal sliding.
UR - http://www.scopus.com/inward/record.url?scp=80655139852&partnerID=8YFLogxK
U2 - 10.3189/002214311798043735
DO - 10.3189/002214311798043735
M3 - Article
AN - SCOPUS:80655139852
SN - 0022-1430
VL - 57
SP - 954
EP - 964
JO - Journal of Glaciology
JF - Journal of Glaciology
IS - 205
ER -