This year, for the summer 2018 field season, Tom returned to Store Glacier with new and improved UAVs (Unmanned Aerial Vehicles, or ‘drones’). These new units had larger lithium-ion batteries that provided a longer flight time allowing us to cover a larger area, as well as a slightly improved carrier-phase GPS setup, recording the UAV location at twice the frequency and theoretically improving the accuracy of our 3D models.
Launching one of the drones.
The beginning of the season saw excellent weather and we were able to fly repeatedly in a number of locations around the field site, including two of the nearby lakes and a large crevasse field downstream of our main camp. Our focus on the lake paid off on the evening of the 7th October, when we noticed that the lake was beginning to drain down a nearby crevasse.
The lake beginning to drain.
The sight of a lake over 1 km2 large draining down a crevasse over 10 metres wide is truly breathtaking. Luckily, we don’t just have pictures – we were also able to capture the after-effects via our UAV surveys. The preliminary maps below show the lake as it looked on the morning of the 7th and the morning of the 8th July – with some awkward red artefacts in the former image.
The lake was approximately 1.3 km2 in area during the UAV flight prior to the lake drainage, and only 0.5 km2 after. Looking at preliminary data, we estimate that as much as 2.8 x 106 cubic metres of water drained to the bed of the ice sheet – that’s over 1000 Olympic-sized swimming pools. Most of this water drained in less than three hours. Tom’s main focus of work from this season’s data will be to analyse the effects of this drainage on the ice sheet, working out why the ice sheet fractured where it did, and the effects that this huge volume of water had on the ice dynamics.
The lake before and after rapid drainage occurred, from the UAV surveys.