(Left to right) Ali Feinberg '00 (holding the weapon that the group brought for protection against bears), MHC geology professor Al Werner; Darrell Kaufman, a professor at Northern Arizona University; Laura Levy '98; Yarrow Axford '97, and graduate student Jason Briner journeyed to the Alaskan wilderness to study glacier sediment as an indicator of climate change
Ali Feinberg '00 examines glacier sediment in Alaska.
For several years, geology professor Al Werner and Darrell Kaufman of Northern Arizona University "kicked round the idea" that Alaskan glacier sediment could be studied as an indicator of climate change in the region. Last summer, they journeyed to the wilds of southwest Alaska to test out the theory, undertaking field research from July 9 to August 4. Their team consisted of Ali Feinberg '00, a self-designed major in environmental geology, and Werner's former students Yarrow Axford '97 and Laura Levy '98. Kaufman serves as an adviser to Axford and Levy, who are now graduate students in geology. The National Science Foundation funded the project.
Werner has conducted research in Alaska for twenty years. The goal of this summer's work was to provide a better understanding of environmental change in Alaska during the last 10,000 years. Scientists know that during the early and middle Holocene (the last 10,000 years of earth history), the climate was warmer than it is now, and that during the last few thousand years, the climate in Alaska has grown cooler. In addition, moraines (glacier debris) fronting glaciers indicate multiple glacier expansions (alternating periods of warmth and cold) during the late Holocene. What is not well known is the timing of these warm and cold events, "a piece of the puzzle critical to interpreting their cause," says Werner. "Knowing when 'things' happened in the past is critical to interpreting cause and effect; unfortunately, age-dating glacier deposits is difficult at best."
Glacier-fed lakes, on the other hand, provide a continuous record of up-valley glacier activity and organic matter (tundra plants and bug parts) that wash into the lake (and that can later be radiocarbon-dated for age control). After being dropped into the field by floatplane, the team mapped the geology in three different valleys and recovered cores from lakes located down-valley from small "well-behaved" glaciers. The researchers used a "fish-finder" to map the lake bottoms of lake basins. "We also used a seismic profiling system that allowed us to 'see' the layering and thickness of the sediment in the lakes," says Werner.
To recover sediment core samples, the team pounded four-inch plastic tubes into the lake bottom. This was done using a platform on pontoons, which the group dubbed "The Banana Smoothie," because of its two big yellow pontoons and the smooth manner in which it pulled the cores out of the mud. A large chain hoist was used to extract the core and bring it to the surface, and the pontoon and the core were then towed back to shore using a boat. On shore, the cores were cut into ten foot-long sections, capped, and labeled so they could be shipped to South Hadley or Arizona. Recovering a single core took an entire day; at each lake the team collected two cores, each twenty to thirty feet long.
Life in the wilderness was not easy. The team did not shower for three and a half weeks, and it rained during all but three days of the trip. There was a violent wind storm, during which three tents blew down, and bugs were in great abundance. "Since we all smelled bad, we didn't notice it," says Feinberg, for whom the expedition was a first crack at field research. She noted, "I was witnessing geologists at work, rather than simply learning about science through textbooks. It was a wonderful experience."
Werner and Feinberg are now examining the cores, which are like a "long, albeit muddy, history book; chapter one is what was deposited last year, and the concluding chapters can take you back 10,000 years," says Werner. They are now working with the health center to X-ray cores as one way to document the layering in the sediment. Levy will do her master's thesis on cores recovered from one of the lakes, while Feinberg will do her honors thesis on cores from another. Axford is finishing her graduate work on the glacial history of a region north and west of this summer's field area.
Visit http://pc53.chm.nau.edu/laura to view photographs from the Alaska trip.