Student Focus

Where Ice Sheets Meet

Aaron Putnam of Chapman, Maine, spent two months as part of a four-person expedition studying the stability of the West Antarctic Ice Sheet. From their base camp in a remote area called the Bottleneck, the scientists made daily excursions, rappelling into ice moats and scaling sheer cliffs to collect rock samples. Photo courtesy of Aaron Putnam

Links Related to this Story

Last winter, University of Maine master's student Aaron Putnam was in the TransAntarctic Mountains on an expedition that included some extreme rock collecting. He and members of a research team rappelled into wind-carved ice moats, scaled sheer cliffs and chipped away at boulders, looking for clues about the stability of the two ice sheets that cover Antarctica.

Their camp was in the Bottleneck, a critical junction between the East and West Antarctic ice sheets. Ice flows through this gap from east to west between the mountains. What scientists have yet to understand is whether ice on the west buttresses ice on the east. If it does, the Bottleneck could provide the only major passageway from one side of the continent to the other.

Furthermore, the fates of the two ice masses would be linked. The West Antarctic Ice Sheet is smaller and more vulnerable to collapse because it sits on bedrock below sea level. If rising seas caused it to disintegrate, scientists wonder what would happen to ice on the eastern side of the mountains. Could enough ice flow through the Bottleneck to destabilize the East Antarctic Ice Sheet?

Part of the answer may lie in the rocks that Putnam and his team collected. At the height of the last Ice Age, Antarctic ice bulged through the mountain gap and, as it receded, left behind so-called "bathtub moraines," rocks and boulders layered in rings on the surrounding mountains. By determining when they were deposited, the scientists hope to define when and how high the ice crept up the mountainsides, and how much the level of the ice has declined since then. That information could help determine if the Bottleneck serves as a wide open valve for east Antarctic ice or if ice flow is limited by the shape of the bedrock and surrounding mountains.

With Putnam on the expedition were Robert Ackert and Sujoy Mukhopadhyay of Harvard University, and mountaineer Peter Braddock. UMaine emeritus professor Harold Borns helped plan the expedition; Brenda Hall, assistant research professor in the Climate Change Institute, is Putnam's adviser. Support came from a $130,135 National Science Foundation grant.

The researchers shipped home about 1,000 pounds of rocks, most of them to Harvard, where they will be analyzed with cosmogenic dating to determine when the rocks were first exposed at the Earth's surface. As soon as rock is exposed to the sky, it is hit by cosmic rays that cause chemical changes in the minerals. These changes create by-products, forms of beryllium, neon and helium, for example. Just how much of these by-products have accumulated provides an indication of how long the rocks have been exposed.

At UMaine, Hall is setting up a lab to conduct cosmogenic dating on the rocks that Putnam sent to Orono. For his thesis in geology, Putnam is focusing on how the rock deposits may indicate how the climate in the Bottleneck region has changed over time.

---

New plants for Maine's cold climes

Landscape horticulture graduate student Ajay Nair is experimenting with ways to cultivate the ornamental Japanese stewartia in colder climes like Maine.

Japanese stewartia is a landscaping tree coveted for its year-round beauty. In the winter, it shows off its multicolored, textured bark. Its summertime blooms look like camellias, and its fall foliage features shades of yellow and red. The biggest drawback for Maine gardeners: Stewartia grows best in USDA Hardiness Zones 6–8. Maine has Zones 3–5.

Researching ways to propagate stewartia in this state is the thesis project of graduate student Ajay Nair, part of ongoing collaboration among the University of Maine, an alumnus, and Maine's ornamental horticulture industry. Nair works with UMaine Associate Professor of Horticulture Donglin Zhang, whose research involves developing new plants to benefit Maine's horticultural industry.

Growing plants in Maine has many challenges, particularly their ability to overwinter. That's why the extensive cold hardiness research going on at UMaine is so important. For instance, recent cold hardiness studies demonstrated that five cultivars of mountain laurel and more than 20 of Atlantic whitecedar can be grown in Zone 4 in central Maine. Such research provides technical guidance for growers and increased consumer confidence.

Nair and Zhang are working with one cold-tolerant clone named Stewartia UMaine (UMaine Silk Camellia), which has been growing well at the university's Littlefield Ornamentals Trial Garden. The tree has brilliant red fall color and biennial flowering. Nair has been experimenting with different rooting media and propagation techniques using seeds, tissue cultures and stem cuttings. He coauthored a paper, with Zhang and graduate student Dongyan Hu, on the rooting and overwintering of stewartia stem cuttings that won first place in the graduate student and presentation competition at the Northeast Regional Meeting of the American Society for Horticultural Science in Washington, D.C. earlier this year.

"We hope to answer questions about propagation, especially the conditions needed for cuttings, so stewartia is easy to cultivate and more commercially viable," says Nair of the nonnative yet noninvasive species.

The three researchers have used DNA markers to determine the relativeness of Stewartia UMaine to 16 named Stewartia taxa. Working in cooperation with colleagues at Harvard University's Arnold Arboretum, the researchers found that Stewartia UMaine is a new cultivar that originated from a gene pool of S. pseudocamellia, S. sinensis and S. koreana. These molecular results will be used as guidance for future Stewartia breeding. Their paper on the discovery won third place in the national graduate student poster competition at the annual American Society for Horticultural Science conference in Las Vegas in July.

Nair, who came to UMaine last year from Kerala Agricultural University in India, also works with University of Maine Cooperative Extension Ornamental Horticulture Specialist Lois Stack on experiments with phlox and rubeckia. They are investigating the effectiveness of plant growth regulators in preventing powdery mildew diseases, which can cause significant losses to growers each season.

Horticulture, including floriculture, is the fastest-growing sector of American agriculture. In 2003, Maine ornamental plant sales were valued at $100 million. Maine horticulture includes more than 780 firms, employing more than 10,000 people.