Measuring Isabel (09.17.03) - Whether or not a hurricane warrants an evacuation is a costly decision. Now new technology is helping scientists decide when evacuation is necessary.
Drowning Cities (05.09.03) - Forecasters predict that the hurricane activity in the Atlantic basin will be well above average this year. And in cities like New Orleans, hurricanes are only part of the problem.
This hurricane season, scientists witnessed one of the busiest months of hurricane activity on record. Now researchers are getting the dirt on the history of these storms and hope their findings will help predict future storm cycles.
Stormy Weather
Nothing can pull Joel Piereth from his seaside paradise in Montauk, New York, except the police. Piereth is never in trouble with the law, but he is in trouble with something else: Mother Nature. It's her ire that kicks up periodic hurricanes that threaten to smash Piereth's cozy trailer to smithereens. That's when the police evacuate.
"If we're told to go, we go," says Piereth, a retired postal worker. "The one thing that I like to keep doing is getting older and in one piece, or in as many pieces as I have left," he jokes.
With climate change increasingly linked to drastic fluctuations in weather, and with more and more people like Piereth seeking peace and solitude near the ocean, scientists are hard pressed to predict the cycles of catastrophic hurricanes that can lay waste to thousands of homes and dozens of lives. Now, Jeff Donnelly, a geologist at Woods Hole Oceanographic Institution, is digging up a more definitive hurricane history by analyzing the sand deposits these storms leave behind on barrier islands, islands parallel to the coast.
"If we go out and find out where hurricanes occur and how often they occur then we look at model simulations of both climate and hurricane occurrence," he says. "[We can] try to sort out well when we get warmer sea surface temperatures does that drive more hurricane activity."
Barrier island, Cape Romain National Wildlife Refuge, Charleston, South Carolina image: US Geological Survey
Not long ago, scientists could only examine hurricane cycles as far back as recorded weather, a few hundred years. Donnelly turned to barrier islands to go back further. Because of a barrier island's height, usually only hurricanes have the magnitude to drive the ocean over them, pushing sand from the seaside to the inshore side, where sand isn't normally seen. This creates a fan-shaped deposit called an overwash fan. Over time, soil covers the overwash fan, creating cake-like layers. Like pushing a straw down through the layers, Donnelly drives a long, hollow pole deep into the inshore side of barrier islands to get his core samples. He examines the layers and uses geologic tools like pollen grains, industrial metal residues and carbon-14 dating to estimate when the sand traces were laid down. "In a few cases we've got something like four or five thousand years worth of a record," he says.
This animation shows how storm surge carries sand to the inshore side (to the right) of a barrier island. With time, the sand is covered by sediment, creating cake-like layers. This animation will automatically play and repeat.
Scientists can plug that data into computer models and try to figure out the relationship between climate change and hurricane cycles. "The key is we want to understand cycles of hurricane over time," says Stan Goldenberg of the Hurricane Research Division of the National Oceanic and Atmospheric Administration (NOAA). "Oftentimes, these kinds of studies can elucidate long-term cycles in activity that can also be tied to climate factors."
Donnelly is searching for that link. "One of the things we hope to gain from this is to be able to look at how hurricane activity has changed over time and whether there's any relationship with how the climate's changed in the last thousand years or so," he says.
Joel Piereth says despite warnings from Mother Nature, he'll keep his heels dug in by the sea: "I've fallen in love with the water. I enjoy the solitude of walking a beach with a pole on my shoulder. I may not catch a thing, except perhaps the sniffles or a cold…but there's just something about the solitude out here."
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