IceBite Blog: Visiting Lake Joyce
IceBite team members Chris McKay (left) and Denis Lacelle prepare to board a helicopter for the ride to Lake Joyce. In the background, Observation Hill.
Credit: M. Marinova
NASA’s IceBite project will spend three austral summers in Antarctica testing ice-penetrating drills for a future mission to Mars. A team of seven scientists recently returned from the first field season, installing scientific probes in the ice and frozen ground, and scouting for sites where the drills will be tested the following year. One of the team members, Margarita Marinova, wrote a blog of the team’s activities. In this second set of entries, she writes about a trip to their first field site, Lake Joyce (S77º 43.138′, E161º 35.829′). There they joined another team of NASA scientists who were studying the lake and its ecosystem.
Nov. 28, 2009. Lake Joyce
After a week of training, preparing, and packing, on November 23 we were ready to leave McMurdo Station for our first field site: Pearse Valley and Lake Joyce. Getting there took about an hour by helicopter, flying over fascinating and beautiful valleys, glaciers, and lakes.
Lake Joyce is a small lake in Pearse Valley, sitting beside the Taylor glacier. Dale Andersen and his team had already been at Lake Joyce for about 5 weeks . They were studying the algal mats at the bottom of the lake, as well as trying to understand the surrounding valley geology. Lake Joyce is ice covered year-round: covered by 6 meters of ice! Yet even the few percent of light which penetrate through the ice are enough to support an algal ecosystem in the lake. Many of the structures on the lake bottom look like what we see in the Archean rock record from about 3 billion years ago, giving us a window into the past.
Dale Andersen getting into the dive hole at Lake Joyce. Andersen’s team studies the algal mats that live in the ice-covered lake.
Credit: M. Marinova
Our goal for visiting Pearse Valley was to study permafrost and the ice table at an intermediate temperature. While it is quite cold at Pearse Valley, there are still a few days during the year when the air temperature gets above freezing. These days are very important in determining how water and ice behave in the system. A few days of temperatures above freezing can result in large amounts of ice and snow melting, forming rivers that recharge lakes, ponds, and the subsurface ice table. In comparison, at our second field site, University Valley, the air temperature never exceeds freezing and only water vapor in the air is available for recharging (adding to) the subsurface ice.
A particular phenomenon we are studying at Pearse Valley is buried snow. Usually water in the subsurface is found either as buried ice or as ice filling the soil pore space. But what about buried snow? This question is of particular interest because when the Phoenix lander was digging into the Martian polar region, it dug through a soft, white substance, probably frozen water, with similar strength and density to snow. Wayne Pollard and Alfonso Davila (who have been part of Dale’s team and will join our team when we go to University Valley) have found many instances of buried ice at Pearse Valley, a possible analogue to what was seen on Mars!
Jen Heldmann and I were very excited by this discovery and are spending time trying to find different examples of this buried snow and understand how it behaves. We have three main sites we are studying: inside a gully, at the top of the gully (not a topographic low), and beside a small pond.
Lake Joyce with the Taylor Glacier in the background.
Credit: M. Marinova
By studying these rather different sites we want to show how widespread this phenomenon is. We will also be instrumenting one of the sites: putting temperature and humidity instruments above and below the snow pack to understand how it behaves throughout the year. Does the snow melt away every year and new snow is buried the next year? Or does the buried snow last through many years? By studying these sites we’ll be both learning about an interesting process on the Earth and furthering our understanding of findings from Mars!
Nov. 30, 2009. The Lake, the Glacier, the Moat – and a Half-frozen Boot
What a productive, fun, and exciting week at Lake Joyce! We deployed a weather station, made numerous measurements of the buried snow, Denis and Wayne collected ice and soil samples to understand the geology of the valley, and Chris checked out the lake ice! On the last night (well it was still light of course :), it seemed that a long, fun walk around was in order! (After all, I could just as well sleep in McMurdo!) So I set off with Bekah Shepard, a member of Dale’s team, to explore around Lake Joyce. It was a beautiful clear and sunny night, and the glaciers turn a softer shade of white as the sun goes lower. We walked around the lake – on the 6-meter thick ice.
The author (Marinova), sitting at the foot of the Taylor glacier, by the moat between the glacier and Lake Joyce.
Credit: Bekah Shepard
You might think that the lake ice grows by snow accumulating on the top and the lake forms by the ice melting at the bottom, but it’s actually exactly the other way around: the ice cover forms from below, at the liquid surface of the lake. This formation of new ice actually helps the water stay liquid, even though the mean air temperature is about -20°C (about -4°F). For water to freeze, it needs to “give up” heat energy. The heat that the freezing ice “gives up” keeps the rest of the lake water liquid. By forming about 30 cm of new ice each year, the 40-meter-deep lake can remain liquid.
At the top, because the air is so dry (hence the name “Dry Valleys of Antarctica”), the ice actually sublimates into the atmosphere. Sublimation is when a material goes from freezing to vapor, without ever turning liquid. This is similar to how your freezer at home works – the air is kept dry and cold to keep frost from building up. (This also makes ice cubes shrink if they are left in the freezer for a long time.) Freeze-drying works the same way.
Glaciers are always impressive. Maybe it’s because I am not used to huge walls of ice, or because they look small from a distance. But actually walking up to the glacier, the size is inspiring! And then to realize that this huge mass flows and moves! Bekah and I were quickly reminded about the flowing and moving – as well as about how warm the day had been – by the loud squeaking and cracking. On warm days a moat forms at the base of the glacier. As the moat freezes at night – and the ice expands – everything cracks. Of course also the moat freezes from the top down, so even though in some areas it may seem like solid ice, it’s actually a thin layer of ice overlying deep water. After an unfortunate step on my part (and a half-frozen boot for the rest of our walk), Bekah and I decided to keep a respectful distance from our giant glacier friend and its moat.
After a productive day, a beautiful walk, and enjoying the magnificence and absolute silence of midnight in Antarctica, I’m off to another cozy night in my sleeping bag.