Tracking Down Hurricanes' Fingerprints in Trees and Stone

hurricane katrina satellite image

Stalagmites and trees probably aren't the first places you'd think to look for records of past hurricanes. But that's exactly what Amy Frappier, a geochemist at Boston College, and her colleagues have been doing for the past few years — investigating the stalagmite formations' growth layers for chemical fingerprints left behind by storms — and are now doing in the caves on Mexico's Yucatan peninsula.

At the same time, a team of researchers from the University of Tennessee has been searching for the same tell-tale fingerprints in tree rings — in samples gathered from a region of woods in Georgia. The trees have provided them with a record of hurricane activity stretching back almost 220 years.

All these recent efforts have focused on bringing to light the likelihood that storms will intensify as the climate continues to change. Because scientists agree that historical records obtained from aircraft and satellites fail to provide an adequate enough picture, there has been growing interest in the budding field of paleotempestology — the study of past tropical cyclone activity through geological proxies.

The Brazil-based Inter-American Institute for Global Change Research recently decided to fund a 6-year project to use this approach to study past cyclone activity in the entire Caribbean basin — an effort that will likely involve several dozen scientists from four different countries.

Though the specific approaches taken by researchers vary — some studying stone, trees or sediment cores from marshes and lakes — they all take advantage of shifts strong storms cause in the ratio of oxygen isotopes in the water they drop. Rain from these storms typically carries more of the lighter oxygen isotopes. In the case of tree-rings, scientists date lighter-colored portions as early-season growth while dating darker portions as late-season growth — with each segment undergoing an examination for the oxygen-isotope content. The techniques used to date stalagmites is similar. Scientists have been able to trace histories dating back 5,000 years using some of these methods.

"By putting together this team of people and tackling the problem from different angles using different techniques and looking at different time scales we will have a better understanding of the spatial and temporal variations in hurricane activity across the entire Caribbean Basin," said Kam-biu Liu, a paleoclimatologist at Louisiana State University who first applied this technique to study hurricanes in the late 1980s.

Via ::Christian Science Monitor: Clues from hurricane 'fingerprints' (newspaper)

Image courtesy of GISuser.com via flickr