By Matthew D. Covington, Jason D. Gulley, David Ochel

Most of the meltwater on the surface of the Greenland Ice Sheet flows in rivers and streams that eventually end in moulins, which are giant holes in the ice that carry the water to the bottom of the glacier. Once meltwater is beneath the ice it can lubricate the bottom of the ice sheet, lift up the ice, and cause the ice to move faster. This may create a double effect, where future increases in melting of the ice during warmer climate may also cause faster sliding and more loss of ice into the sea. However, these processes are not well understood. During a 3‑year project, we have conducted two summer field expeditions, where we measured meltwater and water levels inside of moulins. In the last 2 years of the project, we also conducted two fall expeditions, where we directly explored inside of moulins using a mix of caving and ice climbing techniques. During the presentation, we will share photos, videos, and stories from our adventures on the ice sheet, focusing particularly on our most recent expedition in fall of 2019, and provide a basic explanation of our initial scientific results.

6 Comments

    1. The flights don’t go from NY that time of year, and I actually flew out of Slovenia, where I’ve living for the year. However, you’re right that for our summer field work in Greenland we did fly from NY with the Air National Guard.

    1. Annual snowfall varies a lot from place to place on the ice sheet. However, there are at least some permanent research stations with good snowfall measurements, such as Summit Station. Overall, the best estimates of water added and lost are actually from satellite-based gravity measurements from a system called GRACE. Perhaps surprisingly, most of the snowfall at Summit is in the summer (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015JD023072#:~:text=The%20annual%20mean%20snowfall%20measured,two%20month%20time%20lag%20exists.).

  1. Hi Matt, was your dye (neat color!) picked up anywhere? Had you set dye traps somewhere on the coast beforehand? Do you think -100 meters is about is as far down as you can go in air filled passage? Though maybe you need a bigger sample size to answer that one (I.e. more pits). Rick Banning

    1. Hi Rick,
      We used the dye to measure discharge in the streams rather than for tracing connections, though dye tracing has been used elsewhere on the Greenland Ice Sheet for proving connections. The biggest challenge with that is the huge amount of dilution. You need a lot of dye. For our purposes, to measure flow, we were pumping dye into streams on the ice surface at a known rate. Then we measured concentrations a few hundred feet downstream. From those concentrations, and the known pumping rate, you can calculate how much water is flowing in the channel.

      As for maximum depths, the water level within the ice depends mostly on the thickness of the ice and the gradient. In general, it gets closer to the ice surface the further inland you go (because of lower gradients). So, in the area where we were, where the ice was around 700 m thick, something like 100 m is all you are going to get (though in the summer the water levels can vary daily by nearly 100 m!). Closer to the edge of the ice sheet, even though the ice is thinner, it would be possible to find air-filled cave a bit deeper.

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