Saturday, January 24, 2015

Goodbye to the Dry Valleys

Picture 1: View of the lower portion of Taylor Valley.
The valley floor is approximately two miles wide at this
On Wednesday morning, my colleague Carolyn and I took one last helicopter ride out to the Dry Valleys to collect additional soil samples for her project. This time we were to land at the F6 campsite, which would serve as our focal point for sampling soils along three watersheds located in the general area. One small caveat to this trip was that we heard beforehand that winds coming off of Taylor Glacier and down the valley had really picked up overnight (40-60 mph gusts). While the majority of our helicopter ride across McMurdo Sound was uneventful, it did make for an interesting final leg of the journey upon entering the valley. I had the front passenger seat of the helicopter this time so it allowed me to get some great photos of the valley (Picture 1), though it was hard to keep the camera level due to the turbulence!

Picture 2: Diagram illustrating katabatic winds in 
Antarctica (Source:Alfred Wegner Institute for Polar
Marine Research).
These winds are a weather phenomenon known of katabatic winds. These winds are common in Antarctica and originate from the build-up of cold dense air over the higher elevated ice sheets.  Periodically these air masses will get dislodged, and due its greater density gravity will propel it down the valley as fast moving winds (Pictures 2 & 3). The air itself generally heats up as it moves downhill and this helps remove any excess moisture near the surface helping to keep the Dry Valleys a desert environment. While katabatic winds can generally be in excess of 100 mph, we were fortunate to experience a milder version.

Picture 3: View towards the west end of Lake Fryxall at the
onset of our hike. Note the low level clouds, which are
associated with the katabatic winds.
Unfortunately, the winds were blowing from the direction of our planned two mile hike to the west of end of Lake Fryxall (Picture 3). In addition to the winds, we were both carrying backpacks with our sampling equipment so this was not going to be an easy trip. We slowly made our way up the valley floor using moraines and large boulders as periodic shelter from the winds. It took us about an hour and half to reach our first destination, Delta Stream (we decided to sample the closer watershed, Crescent Stream, on our return trip). After refueling with some peanut butter and jelly sandwiches we collected our samples and then began our return journey. At first, the wind was at our backs which definitely helped push us along. However, it was while we were sampling Crescent Stream that the winds shifted in a cruel twist of fate; they were now blowing directly from the east. Needless to say we were pretty wiped out when we finally made it back to camp. After taking a little break, we sampled the third and final watershed which was a lot closer to the camp itself. 

Picture 4: Nighttime panorama of the Commonwealth Glacier.

Picture 5: Lower Taylor Valley illuminated by the
nighttime sun.
The last night in the field was bittersweet. We had dinner with members of the "stream team" who were also still staying at the campsite. Later in the night, I decided to take one last night in the Dry Valleys. While I will leave the valleys with many memories, one of my favorites is seeing the landscape in the eerie nighttime sun (Pictures 4 & 5). As I previously mentioned, the different direction of sunlight illuminates the landscape in a unique way often revealing secrets that were hidden in plain sight. I hope I can do the same with the samples I collected and add to our overall understanding of how sediments and elements are transported in this unique system. But for now, I decided to just take it all in one last time. While I may never get to see this part of the planet again, I'm extremely grateful to have had this field experience.