IceBite Blog: Visiting Lake Joyce
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.
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.
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.
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.