Friday, June 07, 2013

In Borneo, Stalagmites Tell Modern Story of Rainfall and Climate Change

The formations in the caves of Gunung Mulu reveal a record of prehistorical rain patterns

On the tropical island of Borneo, some of the most spectacular caves in the world also hold a piece of an ongoing climate puzzle.

The caves of Gunung Mulu are a tourist destination and a UNESCO World Heritage Site, with large, open chambers and stunning formations. Those glittering stalagmites, which have been forming for tens of thousands of years, are what provided Georgia Institute of Technology doctoral student Stacy Carolin with a way to investigate how rainfall in this region shifted when past climate changed.

"Stalagmites are a very interesting proxy because they can be very well dated and they can also be measured at high resolution to give us oxygen measurements that we can relate to rainfall," Carolin said.

She analyzed samples that had broken off the formations to see what periods of time during a period called the last glacial period had high rainfall, and which had low rainfall. The last glacial period spanned from 110,000 to 10,000 years ago; during that time the Earth was colder and glaciers covered significantly more land.

What she hoped to discover was whether rainfall in the western tropical Pacific changed at the same time as some of the major climate shifts that scientists know happened during this period. The results of the research were published online yesterday in the journal Science.

Climate scientists find the last glacial period interesting because ice cores in Greenland and ocean sediment cores have shown that during this period there were sharp shifts in global temperatures. These could provide an analogy for what might happen now as our world warms.