I knew something was wrong. I pulled my blindfold off, unzipped my sleeping bag and stared at the ceiling of my tent. The midnight sun had swung around to the north and the wind was up. After three weeks of freezing rain, snow, and cold weather, the night was strangely warm and the low sun was lighting up the early hours. Strong katabatic winds were howling down from the Greenland Ice Sheet distorting my tent’s shape, bouncing its walls off my back. A high-pressure system was forming over the ice sheet and the cold was gone.
Once warm weather starts, huge swaths of surface ice begin to melt with dramatic results. Like a dam bursting, small, gentle streams running out from beneath glaciers can turn into monstrous rivers in less than a day. Last season, the river flowing from our glacier increased by a factor of 200 in one week, and half of that increase occurred in one day. Once the high melt season begins, rivers race out from beneath the front of glaciers until cold weather returns in late summer and the fall freezes them once again.
Because we have tens of thousands of dollars worth of scientific equipment sitting just a few feet above the river, rapidly rising water is a huge concern for us. It doesn’t help that our equipment is strung out along a mile of river. One year ago, after a week of moving instruments up the riverbank to keep them from being swallowed by the rising water, a section of riverbank collapsed taking some expensive things with it.
There is a lot of water stored in the Greenland Ice Sheet. It contains enough fresh water to raise global sea level by 23 feet (7 meters). Snow grows the ice sheet in the winter and when warm weather begins in the summer, a fraction of the ice melts into the ocean. Since we've begun measuring the ice with satellites there has been more melting than growth.1 The Greenland Ice Sheet is shrinking and its meltwater is slowly raising global sea level.
When meltwater first starts to form on the surface of the ice sheet in the spring, water begins to drain through cracks in the ice. These cracks can lead all the way to the base, where the water is stopped by rock. The meltwater must then force its way through torturous channels under the ice sheet as it seeks its way downhill. During this early season melting, the small, convoluted channels under the ice quickly become too small for the increasing volumes of meltwater and the water is backed up as if behind a dam.2
Water pressure under the ice builds and during the warmest part of the day, higher meltwater inputs to the base physically lift the ice (almost like it's floating on water) and the glaciers “jump” downhill. Extremely accurate GPS stations detect this rise and fall of the ice sheet surface as these slugs of meltwater beneath the ice sheet pulse to the rhythm of the sun getting high and low in the sky.3
When the pressure of meltwater to the base of the ice sheet becomes too great, large channels are blown open, releasing huge amounts of dammed-up meltwater at once. Once these less convoluted channels form under a glacier, water pressure under the ice declines and the horizontal motion of glaciers slow down. So while more ice is melting in the warmer summer months, the glaciers are actually moving faster in the cold spring.
Since our field season began, the weather had been especially bad. Almost everyday clouds covered the sky and rain, snow or sleet fell on our tents. Sunny days seemed few and far between. Then a few days ago, a cold, hard rain started and didn’t let up for a day and a half. We were wet and damp and did pretty much everything we could to find excuses to work in our tents. But then the rain stopped and the temperature began climbing. In the morning the sun was out and for the first time since arriving in Greenland, I decided not to wear long underwear.
The day the sun came out we'd scheduled a sampling transect down the river to the ocean, taking water samples every few miles. We’d planned on being away from camp until the next day and were looking forward to a musk ox curry in town. So, with a thermos of coffee in hand, we left camp at 5:30 in the morning and headed for the portal, or mouth, of Leverett Glacier where its river discharges from beneath the ice.
The air was dry and cool and the sun was low on the glacier, lighting up all its shades and colors. Despite my lack of enthusiasm for early mornings and my half-awake proclamations that no work should ever be done so early in the Arctic summer (because it’s always light out) it was a really beautiful. After sampling at the portal we headed back to camp for some pancakes, more coffee and then headed to our next sampling point. As it was turning into a very nice day, and we were expecting the river to burst soon, I checked on all of my instruments next to the river and made sure they were all situated high above the water.
As the day wore on, the sun got warmer and warmer until, well it was actually hot (very unusual in Greenland). Late that afternoon at the fjord I was wearing a t-shirt. I returned to the fjord a few hours later and noticed the rock I’d been sitting on earlier was under at least three feet of water. The river was beginning to rise rapidly.
Phone used a satellite phone to call Andrew Tedstone, Alex Ingle and Michaela Musilova back in camp. They had been away from camp all day on a trek onto the ice sheet, where they were setting up an experiment to measure microbial life on the glacier. The three were exhausted from spending the day carrying heavy equipment up and down steep hills and over the glacier. From town we told them how much the river was rising and that it was up to them to rescue all of our data loggers, instruments, and probes from the rising water. It was a daunting task, one made worse by the fact that they would have to continue moving everything every few hours all night. In town there was nothing to do but (sorry to say) tuck into our musk ox curry and toast our comrades in camp.
That night the dam really burst. The river began the day with a discharge of around 10 cubic meters per second and rose to what we guessed was over 200 by evening. The team in camp stayed up all night moving equipment, some of which needed to be pulled from rock bolts and then re-drilled into cliffs as the river rose. Some of the more expensive equipment far from camp was simply pulled out of the water and dragged far away from the rising river. Better to lose a day of data than risk losing everything (we still have 12 weeks in camp). By the next morning, Alex, Andrew and Michaela saved tens of thousands of dollars of scientific equipment not to mention our field season. The only casualty of the rising river was a bucket (mine of course).
At 8:00 the next morning as the team was dragging themselves up once more to make tea and move equipment one last time, a helicopter flew over camp and circled low, lingering for several minutes. It was a BBC camera crew shooting a nature show about the arctic and they wanted some shots of scientists. In town we met one of their crew who laughed at how “sleepy” our team looked from the air.
Other news from camp:
- Congratulations to Alex and Gabi who are getting married soon! Alex just left camp and is likely getting his kilt together for his Scottish wedding in Poland.
- Foxy Prince and his girlfriend Foxy Princess have returned to camp (see previous posts about the arctic foxes). Everyday for one week straight, Foxy Prince ran through camp early in the morning waking everyone up. He and his girlfriend have a den one hill over from our camp where we suspect they have some pups. Someone got a picture of them, which will be posted soon.
- The musk ox herd has been a regular sight, but they are all on the other side of the river. As our camp is on a bit of land surrounded by large rivers and glaciers, the musk ox likely won’t be making it into camp this year.
- At least five caribou are living near camp, three large bucks and one doe with a little brown fawn (without the Internet I have no idea what the proper term for a young caribou is… a calf? Are the males called bucks and is a female a doe?).
- The mosquitoes are out in force. My field notebook is covered in bug guts, as it’s the best weapon I’ve found for killing them in my tent.
- Sorry to friends and family for not being in better touch—getting in and out of camp has been a challenge. In a few weeks I may get into town again and online (this post was carried out by someone heading home).
1. Velicogna, I., 2009. Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE. Geophyics Research Letters 36, L19503.
2. Bartholomaus, T.C., Anderson, R.S., Anderson, S.P., 2008. Response of glacier basal motion to transient water storage. Nature Geoscience 1, 33-37.
3. Bartholomew, I., Nienow, P., Mair, D., Hubbard, A., King, M.A., Sole, A., 2010. Seasonal evolution of subglacial drainage and acceleration in a Greenland outlet glacier. Nature Geoscience 3, 408-411.
All images credit: Ben Linhoff, Woods Hole Oceanographic Institution
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