Researchers have found an intriguing climate link between the southwestern corner of Australia and a region of eastern Antarctica. When the former suffers a drought, the latter is often battered with heavy snowfalls. More provocative: Several climate models suggest that human activity could be strengthening the connection.
The scientists noticed the link after nearly 30 years of studying Antarctic ice cores extracted from Law Dome, an ice field near Cape Poinsett, which lies almost exactly south of the southwestern tip of Australia. There they found evidence that the area had been experiencing abnormally large amounts of snowfall for several decades. They also knew that southwestern Australia had been suffering from severe droughts for approximately the same time.
So the researchers--climate scientists Tas van Ommen and Vin Morgan of the Australian Antarctic Division in Tasmania--examined the ice-core records from Law Dome going back 750 years. Then they compared the ice-core records with meteorological records to gauge precipitation patterns in southwestern Australia, as well as atmospheric circulation patterns in the Southern Hemisphere for the past 4 decades. As they report online this week in Nature Geoscience, about 40% of the rainfall variations in southwestern Australia were mirrored by snowfall variations at Law Dome. "The connection really stood out," van Ommen says.
More intriguing, the Law Dome snowfall patterns seem to have intensified over the past several decades. The pattern, van Ommen says, is "so unusual that we believe it lies outside the range of natural variation." Because of the link to southwestern Australia, he adds, "the implication is that the drought could be similarly unusual."
Indeed, climate models predict such an anomaly when humanmade carbon dioxide (CO2) emissions over the last century are factored in. According to the models, higher levels of CO2, coupled with reductions in atmospheric ozone, create an atmospheric circulation pattern in the Southern Ocean that brings drier air to the farming regions of southwestern Australia and heavier snows to Law Dome. But as the models show, by boosting CO2 and cutting ozone, the normal cycles can be cut, and that is what seems to be happening now.
It's "a very solid piece of evidence" for the influence of human activity on regional climates, says climate scientist James White of the University of Colorado, Boulder. "Can very odd climate just happen at a time when we humans are also causing unusual climate change?" asks White, who specializes in arctic research. "I wouldn't bet the farm on it."