Tuesday, April 12, 2016

Erector Set...

Bob Busey, Cathy Wilson and Lily Cohen finished up the catchment-wide snow surveys on Friday and Saturday under mostly sunny skies and began preparation for our final task of the trip. The challenge was to construct two mobile snowmelt stations at the NGEE Teller site using the fewest, lightest, shortest, easiest to assemble, pieces of observation equipment, tower infrastructure, hardware and tools. It all needed to fit in the 5ft x 2ft x 2ft belly pod and back seat of a helicopter, and take a day and half to construct and test. Thanks to Bob Busey’s creativity and careful preparation in Fairbanks, we landed at the field site on Saturday with our artfully compact load and got to work building the stations.

One of the novel aspects of the station design was the use of survey tripods as the foundation of the infrastructure. These are easy to carry and set up in any terrain.  Bob designed to stations to mount on top of the tripods with unistrut and interlocking, lightweight aluminum poles. The snow sensor, temperature and relative humidity sensor, net radiometer, game cameras and data logger boxes were then mounted off of this simple scaffold.

While Bob and Lily constructed the tower infrastructure, I dug a pit in a snowdrift banked against a shrub thicket to install Bob’s new snow temperature profiler. The profiler has thermistors spaced every 4 centimeters along a wooden rod that has approximately the same thermal conductivity as snow. When inserted upright into the face of a pit, it continuously measures the temperature of snow from the ground surface up through the snow pack to the top of the ~90cm tall unit. We will use the instrument to assess changes in thermal conductivity in the snow pack as a function of depth and time during snowmelt. After installing and burying the profiler, and running its cables through a trench to the snowmelt station pit, I assisted Lily as she built the “yellow” snowmelt station in the shrub drift, while Bob completed the “blue” runoff observation snowmelt station overlooking the creek.


On Sunday we put the finishing touches on both stations and deployed two pressure transducers in the creek that was already flowing due to the unusually warm early spring temperatures. In fact, areas of shallower snow pack including the “blue” snowmelt station site were shrinking fast, leaving large patches of bare ground that had been snow covered two days earlier.

By Sunday afternoon we were packed up and ready to leave the site. Cathy got one more look at the two completed stations as she ferried the first load of empty action packers and tools back to Nome. She also spotted one of the first grizzlies of the season just a few miles North of the airport. Sunday night was spent reorganizing gear for the snow survey in Barrow this week, and snowmelt survey back at Teller next week.