Predicting the future of Antarctic Ice

Using information gleaned from geologic data from the past 20,000 years,  scientists from Pennsyvania State University (Penn State) will apply new methods to provide a better understanding of the past and current behaviour of Antarctic ice sheets.

Models of ice sheets are elaborate systems of mathematical equations that can be used to produce computer simulations. Scientists use these simulations to understand the interplay between the major processes that affect the climate and ice sheets and to simulate the behavior of Antarctic ice during selected time frames.

These studies are of great interest in projections of climate change, particularly its effect on sea-level rise. "Our research group has been working on statistical methods for complex computer models and observations in recent years, but ice sheets present an entirely new and exciting challenge because their behavior can be very complex and difficult to capture well with current models," Murali Haran, an associate professor of statistics at Penn State.

Because the impacts of climate change vary from place to place, having improved projections of sea-level rise for specific locations is important not only to scientists, but also to policy makers and citizens.

Haran is the principal investigator on the project. The interdisciplinary research team spans two colleges at Penn State and includes scientists in the Department of Statistics, the Department of Meteorology, and the Earth and Environmental Systems Institute.

A new 3-dimensional ice sheet model that the Penn State scientists will use as part of their research has been developed by Penn State senior research associate David Pollard, a co-principal investigator on this project. "Changes in sea level result not only from the effect of climate change on melting ice, but also from its effect on winds and ocean currents," Pollard says.

Associate professor of meteorology Chris Forest, a co-principal investigator on the project, said "We are excited to investigate the impacts of climate change on the ice sheets and to learn how the interactions between the tropics and high latitudes are affecting circulation patterns in both the oceans and Earth's atmosphere."

Haran explains that observational data on ice sheets do not easily lend themselves to accurate predictions from existing statistical methods, partly because the thickness of the ice varies a lot within the ice sheet and partly because some of the data sets contain complicated errors and uncertainties.

He says, "Our work on this project will allow us and others to routinely fit more-sophisticated models to larger data sets than currently can be analyzed at the level of accuracy that is the goal of our work. Our methods will allow us to use as much information as possible for drawing useful scientific conclusions -- even information from the very large Antarctic-ice data sets that now present many statistical challenges."

The statistical methods developed by the Penn State group also are likely to be more broadly applicable across a range of disciplines where computer models with high-dimensional output are common, including ecology, hydrology, mechanical engineering, and astronomy.

"One of the joys of being a statistician is working with top-notch scientists on a difficult problem and working together to glean as much information as possible from the available data," Haran says. "To address the challenges involved in this research, it is very important to have long-term collaborations with experts in statistical methods, ice sheet modeling, geologic data, computing, and mechanisms that affect climate.

This project assembles a team of researchers with expertise in these widely dispersed areas. In addition to Haran, who is a statistician; Pollard, who is an expert in ice-sheet models affiliated with Penn State's Earth and Environmental Systems Institute (EESI); and Forest, who is an expert on understanding and designing climate model experiments, the research team includes Patrick Applegate, a research associate in EESI who has worked extensively on interpreting geological data from glaciated environments. 'This grant provides a great opportunity to look at what geologic data have to say about the past and future of the Antarctic Ice Sheets," Applegate says.

The National Science Foundation's Division of Mathematical Sciences has awarded more than $500,000 to Penn State to develop new statistical methods needed for predicting the future of Antarctic ice sheets.

"This funding will allow us to work on fascinating, challenging, and important scientific problems while developing cutting-edge statistics methods that could give vulnerable populations more time to prepare for some of the effects of our rapidly changing climate," says Murali Haran, an associate professor of statistics at Penn State.

Haran, Forest, Pollard and Applegate are also active members of a multi-institution NSF Sustainability Research Network (SCRiM) that was established last year, with Penn State as its hub. "Penn State has world-class departments in meteorology, geosciences, and statistics, so it is not surprising that there is a strong Penn State presence in research on the boundary between statistics and climate science," Haran says . "Major research programs like these allow us to involve graduate and undergraduate students from statistics and climate science, so we get to work on challenging and interesting problems while also training the next generation of interdisciplinary scientists."