PSU Magazine Winter 2006

'f 1 he retreat of glaciers in the American West is dramatic. But the changes hap– pening at the Nonh and South poles are even more alarming. Christina Hulbe, assistant professor of geology at Portland Stale, says the highest rate of warming on the planet is happening on the Antarctic Penin– sula, nearly a thousand miles south of the Lip of South America. ln March 2002, a chunk of ice about the size of Rhode Island broke off the Larsen lee Shelf following one of the warmest summers on record. The shelf, approximately 12,000 years old, had survived many fiuctua– tions in the Earth's climate. Hulbe and colleagues from University of Maryland and the ational Snow and lee Data Center in Boulder, Colorado, con– cluded that summer melt-water had filled pre-existing crevasses. Because water is more dense than the ice around it, it caused those crevasses to propagate downward through the full thickness of the ice, shattering the entire shelf. The melt-water was created over years of warmer-than-usual summers; the mean annual temperature in Antarctica has been rising steadily si nee the late 1940s. Hulbe uses computer models Lo study this phenomenon, and in 2002 was awarded a grant from the National Science Foundation that, along with an ongoing grant from NASA, will sup– port her efforts to see whether such massive breakup events could take place on the larger ice shelves farther south on the continent. "These ice shelves-the floating extensions of moumain glaciers-are catastrophically disintegrating," she says. At the other end of the planet, Hulbe is studying Heinrich events: the depositing of debris onto the ocean floor from floating icebergs. Scientists have found this debris as far south as Portugal , and Hulbe is studying what this sediment record might tell us about cooling and warming periods throughout history. "ll allows us Lo connect present day observations Lo events Lens of thou– sands of years ago," she says. he projects Hulbe works on are mostly done from the comfort of the PSU campus, where she receives numerical data from thousands of miles away. When she visits glaciers these days, it's on summer hikes in the Cascades. Hulbe loves being in the mountains, a carry-over from her childhood when she lived in tent camps for weeks at a time in Northern California with her geologist father. ulbe is quick to poim out that there are hundreds of variables that accoum for changes in the Antarctic landscape, and a lot of them have nothing to do with global warming. ln fact, science has shown that some parts of Antarctica have actually gotten a lit– tle cooler in recent decades , although within a normal range if you look at the big picture, she says. But the cata– strophic events such as on the Larsen lee Shelf are definitely climate-related. Why is the ice in Amarctica impor– tant? It could be a sign of things to come. Hulbe says breakups of old ice shelves could trigger runaway erosion of the ice sheets they're connected to. If all the ice in Western Antarctica were to slide into the ocean, sea levels worldwide would rise as much as five meters. By contrast, if all the world's mountain glaciers melted, sea levels would rise only about half a meter, she says. □ WINTER 2006 PSU MAGAZINE 19