Unraveling Byrd Glacier

News

By Leigh Stearns
Summer 2011

I first started studying Byrd Glacier almost 10 years ago as a new PhD student at the University of Maine. I was using a new suite of NASA satellite imagery, capable of imaging farther south than previous sensors, to derive ice velocities. Byrd Glacier was my first guinea pig, and I spent almost 18 months pouring over images, trying to develop the methodology that would allow us to quantify how fast the glacier flows using repeat imagery.

Byrd Glacier is one of the largest glaciers in Antarctica – 20 km wide and 200 km long – and transports ice from the interior of East Antarctica into the Ross Ice Shelf. Despite its size and potential sea level contribution, relatively little is known about it. The general consensus was that Byrd, like many East Antarctic glaciers, was slow, boring and not worth the scientific scrutiny.

Through detailed remote sensing work, we showed that Byrd Glacier is actually more dynamic than originally thought. Our data showed that the whole glacier accelerated more than 10 percent over a 6-10 month interval in 2006. This speed-up occurred right after two subglacial lakes in the catchment of Byrd drained; water from these lakes likely drained along the ice-bed boundary of Byrd Glacier, lubricating it and causing acceleration.

Antenna

Leigh Stearns and Peter Braddock wire up a GPS antenna for a winter-over monitoring site on Byrd glacier. Photo courtesy of Kristin Schild.

 

Byrd Glacier’s sensitivity to subglacial water brought renewed interest and funding support. Only one other field team has ever conducted field measurements on Byrd (in the 1970s), and satellite coverage, while covering a large spatial area, fails to capture the fine-scale changes in ice motion (most velocities derived from satellite imagery are averaged over several months – the time separation between two usable cloud-free images). Our current NSF project focuses on understanding the small-scale changes that Byrd undergoes – whether due to tides, subglacial water, or ocean circulation – and how these changes in ice flow propagate up the glacier. Only when we understand the physical processes that control how fast Byrd Glacier flows can we model how it will behave in a warming climate.

In November, our field team of six (two graduate students, two professional mountaineers, and two lead scientists -- myself and my PhD advisor) headed to Antarctica to deploy 28 GPS units on and around Byrd Glacier. The GPS receivers are secured to the ice with metal poles, and they record the precise position of these poles every five seconds. Most (21) of the instruments were “summer-only” GPS units and stayed on the glacier from November to February; these units were relatively small and light (~75 lbs) and were charged with one 40-watt solar panel. Although logistically much more difficult, we also want to know how the glacier behaves throughout the winter. We deployed seven units that will (hopefully) record data all year long; three of these are on the trunk of the glacier, two are over the subglacial lakes, and two are on bedrock (our base stations). Each of these units has several 50 or 80-watt solar panels, wind turbines, and 10 car batteries; the total weight of each ‘winter-over’ unit is over 1,000 lbs (not including all the gear needed to install them). Despite their skepticism and disbelief, the pilots and logistics coordinators in Antarctica provided wonderful support, and we managed to get all this gear out to the glacier.

I imagine (honestly, I don’t know!) that seeing Byrd Glacier for the first time is akin to internet dating. I had studied every feature with satellite imagery in such detail and with such familiarity that I felt I knew Byrd intimately. But, when we got there, I was surprised – the adjacent cliffs were more precipitous and colorful with red and grey metamorphic rocks; the glacier surface, with crevasses that looked so organized in imagery, was chaotic and rough; and the enormity of the glacier, which seemed so manageable on my computer screen, was hard to grasp.

Despite our fair share of weather delays, unbearably cold winds, faulty cables, dead batteries, and constraints on both fuel and the pilots’ time, we successfully deployed and retrieved almost all of the GPS units. Seven ‘winter-over’ units are still out there, hopefully resilient to the strong katabatic winds and recording data right now. We’ll find out how they fared when we return next November. In the meantime, we’ll be busy processing GPS data and new high-resolution imagery to try to unravel what makes Byrd Glacier tick.