By Sarah Mellies, Brooke Stamper, and Salvatore G. Candela
Six members of the Juneau Icefield Research Program set out to take the annual GPS (global positioning system) measurements of one of the few glaciers advancing in the Northern Hemisphere.
The movement of Taku Glacier has gone through many changes in history. Currently, the Taku Glacier is acting as a land-terminating glacier because it is pushing into land known as Oozy Flats. About 120 years ago it was a tidewater glacier, since its tongue was flowing into the inlet as opposed to land. Since Oozy Flats is only a small patch of land, Taku Glacier could end up being a tidewater glacier again. The lower reaches of the glacier can be considered a “piedmont lobe”, resulting from the fact that it flows out of its constraining valley into a broader, less constricted area where it spreads out to fill the broad mudflat (much the way molasses would flow across a plate).
To track the movement of glaciers, scientists rely on data taken from satellites, airplanes, and people on the ground. What's the reason for three different data sets? To triple check! Six JIRPers participated in tracking the Taku Glacier on the ground this year. Our goal was to use survey-quality GPS to map the position of the glacier’s extent to see if the tongue is still moving forward into the land and, if so, at what speed.
To speed up the survey work, the team divided into two groups. The first was lead by Scott McGee, JIRP’s field logistics manager, the second by Uwe Hofmann, a staff representative from Beuth University of Applied Sciences in Berlin. For several years, Beuth University has supported JIRP with surveying equipment and provided opportunities for German students to travel to Alaska – a great cultural exchange opportunity. Each leader took two students, to form the Taku West and the Taku East surveying teams. Scott, Brooke and Salvatore headed to the west, while Uwe, Pat and Sarah took the east path. Both groups walked along the terminus (the furthest extent of the glacier ice) taking GPS coordinates at regular intervals.
With the approximate center of the glacier as our starting point, we headed out into the Martian-like landscape of the Taku Glacier terminus. Fighting knee deep mud, frigid glacier streams and bushwhacking that would make a grizzly bear cry, we worked our way around approximately 60% of the 9.2km total perimeter distance of the glacier's broad terminus. In previous years, wide meandering streams stopped teams from covering more ground, a problem we hoped to solve by bringing a small inflatable boat. When we reached the banks of the marginal rivers, our progress ground to a halt as we looked out across large, very fast turbid rivers – far too fast for our Gilligan-sized ship. So much for our dingy. To get around this obstacle, we had to improvise, as is often the case with field work. In order to bypass these inconveniently placed streams, we had to climb nearly 1000 feet up glacier, navigating several crevasse fields before descending back down to the glacier’s edge to continue our survey.
The results of our survey are shown in the figure below, with 2012’s results also shown for comparison. In the figure, the terminus position (the furthest extent of visible ice) in 2012 is shown as black lines, and the 2013 extent as red lines. Right off the bat, we see that the glacier has advanced about ¼ kilometer (800 feet) since the aerial photographs of the base map were taken in 1998. Second, we can see that the glacier terminus has advanced a further 10 to 30 meters (35–100 feet) over most of its perimeter during the past year. This advance isn’t uniform, as is demonstrated by the seven insets in the figure, described in the figure caption.
The terminus shows no sign of stopping its advance, much to the dismay of the trees, shrubs and wildlife that call Oozy Flats home. It is likely that if this glacier continues to advance, it will someday again be a tidewater glacier as it continues to advance towards the Taku River.