We just finished a crazy few days of sampling and I’m only now, back in Seattle, getting a moment to assimilate all of it. The Icy World team from JPL arrived late in the day on May 1, and we wasted no time getting started with field work. The primary mission was to re-sample a number of shallow, methane rich lakes that the team had sampled in October, just as the lakes were starting to freeze. What we quickly discovered at the first lake we visited however, was that a particularly cold winter and unusually thin snow cover had frozen most of the lakes straight through to the bottom. This made it impossible to recover instruments deployed in the fall or to sample lake water. Fortunately not all of the team’s work depended on lake water. We recovered ice cores from several lakes and measured the flux of methane from the boreholes.
No water in this lake. Kevin Hand and Andrew Klesh prepare to section an ice core that extends all the way to the lake sediment.
The ice from these lakes is very interesting. As it forms it traps bubbles of methane; the ice looks like a frozen glass of champagne. If you find a spot directly over an active methane “seep” the bubbles can be huge. In one spot our drill broke through to a methane pocket large enough to choke out the gas powered drill motor. We gave that hole the “lighter test” – a borehole with a high methane concentration will actually catch fire. This one burned intensely for around five seconds!
Photo courtesy of the JPL Icy Worlds project. This photo was taken while we were working at the ice edge. I like it because it shows something I hadn’t considered before – ice algae growing on the top of rafted sea ice. Normally we think of growth as occurring only on the bottom of sea ice. There is a lot of rafted ice along pressure ridges however, perhaps we’ve been underestimating the space available for ice algae to grow.
After two days of sampling lake ice we switched things up and returned to the ice edge near where I had sampled frost flowers on April 30. The lead was open again and the whaling crew had their boats in position for the first whales of the season. It was extremely kind of them to allow us temporary use of their forward whaling camp – the Bowhead whales started to appear while we were there and they could have viewed our presence as a distraction or intrusion (for the whales and the whalers). In addition to collecting more frost flowers and taking some spectacular images of the ice edge it was great to check out the whaling operation up close. The hunters really have whale behavior dialed. When the lead opened we were given a prediction of when the whales would arrive – which was accurate to within a couple of hours, and were told that the Beluga whales would lead the larger Bowheads by about two hours. Not long after the Belugas started swimming past us at a leisurely pace we saw Bowheads breaching in the distance!
Lewis Brower, ready for the hunt to begin. Lewis Brower first introduced me to sea ice in 2009. Many thanks Lewis, and good luck this season! I was told that the hide boat that he is in is around 60 years old – that boat has seen a lot of whales and a lot of change to Barrow.
It’s coming right for us! A Beluga dives under the ice edge. Not long after the Belugas started passing us we could see Bowhead whales breaching in the distance.
The next day (now starting to show a little exhaustion) we returned to the lakes, this time finding some with a little water left in them. In addition to ice and water samples the team collected some amazing footage of the under-ice lake ecosystem, including a couple of sizable whitefish shown in the video below (Video courtesy of the Nasa Astrobiology Institute’s Icy Worlds project at JPL). When I see a lot of biomass like that (also represented by the sizable microbial mats in the lake) I think energy. The interesting thing that this video illustrates to me is the amount of energy that can be contained in a shallow water column underneath a lot of ice – though of course these lakes are most energy rich in the summer, when they are well oxygenated and full of phytoplankton fixing carbon. In the winter however, the flux of methane to these lake should serve as a continued carbon source – with methanotrophic bacteria feeding small protists, which are fed on by larger lake organisms. That’s a testable hypothesis and one that would be worth following up on.
One more day of lake sampling (and a couple of long nights in the lab) saw us to the end of the field effort. It was one of my most memorable trips to Barrow, and a very successful sampling effort. Many thanks to our guides at Umiaq, and to Icy Worlds for letting me tag along…
