TY - JOUR

T1 - Supraglacial lake drainage at a fast-flowing Greenlandic outlet glacier

AU - Chudley, Thomas

AU - Christoffersen, Poul

AU - Doyle, Samuel

AU - Bougamont, Marion

AU - Schoonman, Charlotte

AU - Hubbard, Bryn

AU - James, Michael

N1 - Copyright © 2019 National Academy of Sciences.

PY - 2019/12/17

Y1 - 2019/12/17

N2 - Supraglacial lake drainage events influence Greenland Ice Sheet dynamics on hourly to interannual timescales. However, direct observations are rare, and, to date, no in situ studies exist from fast-flowing sectors of the ice sheet. Here, we present observations of a rapid lake drainage event at Store Glacier, west Greenland, in 2018. The drainage event transported 4.8 x 10(6) m(3) of meltwater to the glacier bed in similar to 5 h, reducing the lake to a third of its original volume. During drainage, the local ice surface rose by 0.55 m, and surface velocity increased from 2.0 m.d(-1) to 5.3 m.d(-1). Dynamic responses were greatest similar to 4 km downstream from the lake, which we interpret as an area of transient water storage constrained by basal topography. Drainage initiated, without any precursory trigger, when the lake expanded and reactivated a preexisting fracture that had been responsible for a drainage event 1 y earlier. Since formation, this fracture had advected similar to 500 m from the lakes deepest point, meaning the lake did not fully drain. Partial drainage events have previously been assumed to occur slowly via lake overtopping, with a comparatively small dynamic influence. In contrast, our findings show that partial drainage events can be caused by hydrofracture, producing new hydrological connections that continue to concentrate the supply of surface meltwater to the bed of the ice sheet throughout the melt season. Our findings therefore indicate that the quantity and resultant dynamic influence of rapid lake drainages are likely being underestimated.

AB - Supraglacial lake drainage events influence Greenland Ice Sheet dynamics on hourly to interannual timescales. However, direct observations are rare, and, to date, no in situ studies exist from fast-flowing sectors of the ice sheet. Here, we present observations of a rapid lake drainage event at Store Glacier, west Greenland, in 2018. The drainage event transported 4.8 x 10(6) m(3) of meltwater to the glacier bed in similar to 5 h, reducing the lake to a third of its original volume. During drainage, the local ice surface rose by 0.55 m, and surface velocity increased from 2.0 m.d(-1) to 5.3 m.d(-1). Dynamic responses were greatest similar to 4 km downstream from the lake, which we interpret as an area of transient water storage constrained by basal topography. Drainage initiated, without any precursory trigger, when the lake expanded and reactivated a preexisting fracture that had been responsible for a drainage event 1 y earlier. Since formation, this fracture had advected similar to 500 m from the lakes deepest point, meaning the lake did not fully drain. Partial drainage events have previously been assumed to occur slowly via lake overtopping, with a comparatively small dynamic influence. In contrast, our findings show that partial drainage events can be caused by hydrofracture, producing new hydrological connections that continue to concentrate the supply of surface meltwater to the bed of the ice sheet throughout the melt season. Our findings therefore indicate that the quantity and resultant dynamic influence of rapid lake drainages are likely being underestimated.

U2 - 10.1073/pnas.1913685116

DO - 10.1073/pnas.1913685116

M3 - Journal article

C2 - 31792177

VL - 116

SP - 25468

EP - 25477

JO - Proceedings of the National Academy of Sciences of the United States of America

JF - Proceedings of the National Academy of Sciences of the United States of America

SN - 0027-8424

IS - 51

ER -