PSU Researcher to Give Local Perspective to Global Warming Issues

June 16th, 2006 by Adam

“How do you take mud from the bottom of Squam Lake and reconstruct environmental conditions in the lake when the mud was deposited 100, 200 or even 1,000 years ago?” That question characterizes the work of Mike Prentice, paleoclimatologist and research associate professor with the Center for the Environment and the meteorology program at Plymouth State University.

“Looking back more than 50 or 100 years provides a better context for assessing the impact of current development on the lakes,” states Prentice. “We can see past natural fluctuations in the lake environment and whether they might offset or add to current impacts.” A variety of chemical techniques can provide a better understanding of what northern New England’s environment was like before humans, the industrial revolution and recent population growth, which can then be compared to present day conditions.

Prentice hopes to begin sampling from Squam Lake soon. He will introduce PSU graduate students to the techniques he himself has applied in world-wide locations including Antarctica and New Guinea to understand global warming and rising sea levels. At the same time, he will be gearing up for a return to Antarctica in November to begin a new research project investigating the stability of the Antarctic climate and the West Antarctic Ice Sheet. Prentice will be the principal investigator on a $600,000 grant he has received from the National Science Foundation with collaborators at the University of Washington and the U.S. Army Cold Regions Research and Engineering Laboratory.

“National Science Foundation (NSF) grants are the most prestigious to be awarded,” says Steve Kahl, director of the Center for the Environment. “Mike saw PSU’s emerging environmental program and the already established meteorology program as a good fit for collaboration and support of his research initiatives.” Kahl looks forward to Prentice’s research focus helping to broaden the scope of the Center for the Environment. “Climate change has policy, social and economic implications. The more ways you can look at the bigger picture and gain a better understanding of the situation, the better prepared we can be to address the questions that emerge.”

“Paleoclimatology,” Prentice explains, “is the study of past weather using the characteristics of proxy materials, such as shells, pollen, mud or ice, whose formation is influenced by the weather. Current techniques for analyzing these materials permit detailed climate reconstructions that can be as reliable as thermometer records. For many regions of the world with short or no instrumental records, proxy measurements of climate change produced from a core sample, such as a tree or lake sediment, are all that is available.” He added that paleorecord quality depends on understanding how modern weather, hydrology and biology are recorded in natural materials forming today. More to the point, Prentice says the question to ask is, “Because of development or global warming, are our environments—a lake in New Hampshire, an ice sheet in Antarctica, or a tropical rainforest in New Guinea—crossing thresholds to a point where rapid deterioration is irreversible? You’ll get a better answer to this question if you have a long record that reaches back to before the use of thermometers.”

As an undergraduate at Princeton University, where he received his bachelor’s in geological sciences, Prentice first began studying paleoclimate. His senior thesis project (through the New Hampshire Office of State Planning) was to develop a manual for implementing a Wild and Scenic Rivers plan for the Baker River. It evolved into a presentation on the glacial history of the Baker River Valley.

His work caught the attention of researchers at the University of Maine, where Prentice pursued his master’s degree in geological sciences under G.H. Denton, professor of earth science. From 1978 to 1982, Prentice traveled to Antarctica during the “summer seasons” to study the history of the West Antarctic Ice Sheet. “In predictions for global warming, the West Antarctic Ice Sheet is a major concern because its collapse would cause sea level to rise about 16 feet,” explains Prentice. As the world’s only marine ice sheet held in check solely by floating ice-shelves, it is considered by many to be unstable, and thought to have collapsed in the geologic past.

“The credibility of such claims has always been questioned, but the evidence that collapse may now be underway has become surprisingly strong,” says Prentice. That, coupled with recent changes observed in Greenland, and the devastating effect a large rise in sea level would have, give the claims new clout. So Prentice is headed back to Antarctica armed with advanced techniques to re-examine contradictory evidence about the past stability of the ice sheet.

In the late 1980s, Prentice received his doctorate from Brown University under Professor R.K. Matthews, a world expert in sea level change. Matthews discovered the primary evidence indicating the past collapse of the West Antarctic Ice Sheet, not in Antarctica, but in the tropics from ocean fossils such as coral reefs. While at Brown, Prentice worked mainly with sediment cores from the sea-floor to track ocean chemistry changes that were attributed to Antarctic changes. However, he continued to travel to Antarctica endeavoring to obtain agreement between Antarctic and tropical ocean records.

It was at the University of Maine, as a post doctoral researcher and later as an assistant professor, that Prentice began to sense a deeper scientific problem. On the one hand, the prevailing interpretation of tropical ocean-sediment records assumed that the temperature of the tropics remained constant. Therefore, the changes measured in tropical core samples could only be the result of one other possible cause: changes in the Antarctic ice sheet. On the other hand, it had been reported that tropical glaciers, found today at high altitudes, had been more extensive in the past. If these glaciers had expanded to larger sizes and then contracted to near extinction, Prentice knew it must be as a result of tropical temperature change. The western tropical Pacific is a prime example. Because the climate there was considered more stable than anywhere else in the tropics, one would not expect to find evidence of melting glaciers, and yet in the high mountains of New Guinea, which overlook the western Pacific, there was evidence of expanded glaciers.

Explaining the discrepancies between actual observations and accepted theory was too great a challenge to resist, and so with NSF funding, Prentice began the first of several expeditions into interior New Guinea. This effort was enhanced when he moved to the University of New Hampshire in the mid-1990s attracted by the paleoclimate work there on a long ice core out of Greenland. According to Prentice, this was a revolutionary record because it was far more detailed than previous records and documented that most large changes in climate were abrupt, occurring in periods as short as a decade.

As it turns out, the evidence of New Guinea glacier change was vastly underestimated and Prentice is now at work reconstructing it. However, in order to obtain the time resolution of an ice-core record, he is producing paleoclimate records from sediment cores raised from high-elevation lakes in New Guinea. He explains, “New Guinea lake sediment records could rival the Greenland ice core records in importance. But, the remoteness and political turmoil of the region as well as the absence of weather information pose major obstacles.” Enter Plymouth State University.

PSU’s strength in meteorology is helping Prentice to obtain funding for a New Guinea weather program that would, in turn, further strengthen PSU meteorology. “If we can clarify the meteorology of the New Guinea high mountains,” says Prentice, “then we are in position to understand how this signal is imprinted into lake sediments. We can use lake sediment cores to extend the climate record back in time.” Prentice views work on the history of New Hampshire’s lakes and lakes in the New Guinea highlands as mutually supportive. Because the high mountains of New Guinea represent islands of cool, wet climate in the tropics, and because the lakes there were created by glaciers and so are young, they share many traits with New Hampshire lakes. Given those similarities, their comparison can facilitate new insights into each.

“A record of 14 NSF grants as well as grants from other public and private sources demonstrate that Mike is a phenomenal researcher,” according to Kahl, “Having a versatile paleoclimatologist join our existing research staff consisting of a hydrologist, a community planner, a freshwater and marine chemist and a limnologist, adds breadth to address environmental policy questions and issues in a more comprehensive fashion.”

Plymouth State University (PSU) is a regional comprehensive university offering a rich, student-focused learning environment for both undergraduate and graduate students. PSU offers 42 majors and 62 minors in programs that include education, business, humanities, arts, and natural and social sciences. The College of Graduate Studies offers coursework that promotes research, best practices and reflection in locations on- and off-campus as well as online. For non-traditional students, PSU’s Frost School of Continuing and Professional Studies offers working professionals opportunities to pursue an undergraduate degree by attending classes in the evenings, weekends and online. Located in a beautiful New England setting, Plymouth State University has been recognized as one of the “Best in the Northeast” by The Princeton Review.