Development and application of a time-lapse photograph analysis method to investigate the link between tidewater glacier flow variations and supraglacial lake drainage events

Abstract

Marine-terminating glaciers may experience seasonal and short-term flow variations, which can impact rates of ice flux through the glacier terminus. We explore the relationship between variability in the flow of a large tidewater glacier (Belcher Glacier, Nunavut, Canada), the seasonal cycle of surface meltwater production and the rapid drainage of supraglacial lakes. We demonstrate a novel method for analyzing time-lapse photography to quantify lake area change rates (a proxy for net filling and drainage rates) and develop a typology of lake drainage styles. GPS records of ice motion reveal four flow acceleration events which can be linked to lake drainage events discovered in the time-lapse photography. These events are superimposed on a longer pattern of velocity variation that is linked to seasonal variation in surface melting. At the terminus of the glacier, the ice displacement associated with the lake drainage events constitutes ∼10% of the seasonally accelerated displacement or 0.4% of the total annual ice displacement (336 m a−1). While the immediate ice response to these individual perturbations may be small, these drainage events may enhance overall seasonal acceleration by opening and/or sustaining meltwater conduits to the glacier bed.

Modelling environmental influences on calving at Helheim Glacier in eastern Greenland

“…The results presented here indicate that changes in basal water pressure leading to velocity changes of this magnitude can in fact have a strong influence on modelled calving rates. The finding supports previous tidewater glacier modelling work (Vieli et al, 2000) and observations at other tidewater glaciers (Kamb et al, 1994;Sugiyama et al, 2011;Danielson and Sharp, 2013) which had already observed a significant dynamic response to changes in basal water pressure, and highlights that changes in basal conditions should not be excluded as an important influence on tidewater glaciers. The link between changes in air temperature and run-off, and changes in velocity may, however, be complicated.…”

“…Selecting the values of cwd to use was challenging as no measurements of observed water depth have been published, and likely values are difficult to predict given the changing volume of crevasses as ice advects downstream, and the probable high rate of drainage in the fractured area around the terminus. Observations have shown that water-filled crevasses can occur even near the calving margin (Danielson and Sharp, 2013), so it is at least known that high water depths are possible in this region, and may become more frequent if the trend of increasing surface ablation continues. If a hydraulic connection exists between the glacier surface and the bed, surface meltwater can also affect the terminus behaviour by altering basal water pressure, and hence sliding velocity.…”

Rapidly changing subglacial hydrological pathways at a tidewater glacier revealed through simultaneous observations of water pressure, supraglacial lakes, meltwater plumes and surface velocities

“…This water often contains entrained subglacial sediment, giving the lake a turbid appearance. Where such connections exist, the water level can be used as a measure of basal water pressure (Danielson and Sharp, 2013).…”

Assessment of ice-dam collapse by time-lapse photos at the Perito Moreno glacier, Argentina

“…glaciers. Both monosopic and stereoscopic modes have been used successfully in glaciological applications since the 90s (Harrison, 1992;Hashimoto et al, 2009;Ahn and Box, 2010;Svanem, 2010, Maas et al, 2010Rivera et al, 2012;Danielson and Sharp, 2013).…”