Which side of Florida gets hit by stronger hurricanes?

Researchers dig deep to find the answer

Dr. Joanne Muller (left) and Ilexxis Morales (right) using a hand coring technique, with a 3-meter core and core candles around the aluminum pipe, in Florida's Indian River Lagoon. (James Javaruski)

JACKSONVILLE, Fla. – Deep below the sand along the coast you can find signs of Florida’s past hurricanes locked in the layers.

The deeper you dig, the farther back in time you see revealing ocean tempests dating back as to 850 A.D.

The surprising sand record “shows that at least for the past 170 years, Florida’s Atlantic Coast has been hit by fewer intense hurricanes than the state’s Gulf Coast,” according to Ilexxis Morales, a graduate student in the Environmental Science program at Florida Gulf Coast University.

Morales is the lead author on a study extending the area’s hurricane record beyond when many written observations began in the 1850s.

Her record is extending back thousands of years using sediment cores as a proxy. Hurricanes leave behind a coarser deposit distinctive enough to be called a “tempest.” It appears different than the dark organic matter found in most samples.

“When a large storm comes through the area,” says Morales, “it picks up light-colored sand from the beach and deposits it in the lagoon.” Because the grains of sand deposited by large storms are coarser than the organic-rich mud, researchers can detect ancient tempest deposits using simple grain-size analyses.

Discolorations highlight areas for scientists to carbon date to determine when the sand was deposited.

(a) Core shows sand beds of Hurricanes Audrey and Rita, separated by a few centimeters of muddy organic-rich marsh sediment. (b) Shows sand of Hurricanes Ike and Rita. Marsh plants, in growth position and rooted in the buried marsh surface, are encased in Tropical Cyclone Rita's sand bed. (Jennifer Collins USF)

Morales and her co-authors, Joanne Muller and James Javaruski, collected sediment cores from a series of lagoons tucked behind narrow barrier islands along the state’s eastern coast and preliminary results suggest that there are fewer visible tempestites there compared to those analyzed from the West Coast.

The results hint that the pattern of more major hurricanes hitting Florida’s Gulf Coast may extend thousands of years back in time.

Researchers used sediment data from actual storms (red) and compared it with a computer statistical model to estimate reconstructed storm activity from 500 AD to 1850 AD (blue).

Researchers used sediment data from actual storms (red) and compared it with a computer statistical model to estimate reconstructed storm activity from 500 AD to 1850 AD.

Which begs the question are hurricanes getting stronger?

This season screams all the hallmarks that it’s happening. There have been six major storms when typically three occur during an average season.

Hurricane Iota became a Category 5 hurricane, marking the fifth year in a row in which at least one Category 5 storm formed. It was the second-strongest November hurricane on record, behind only the 1932 Cuba hurricane. Even after weakening slightly, Iota was still the strongest hurricane to hit Nicaragua as a high-end Category 4 hurricane.

Hurricane Iota landfall second Category 4 storm behind Eta to hit within 15 miles of each other in NE Nicaragua. (wjxt)

Before that Hurricane Laura was the strongest landfalling storm to hit Louisiana since tying the 1856 Last Island hurricane.

Once complete this study could help researchers determine whether changes observed in the longer storm record can be attributed to human-induced climate change.

In the meantime, evidence is seen in the satellites photographing increasing major Category 3 or higher hurricanes. “The trend is there and it is real,” according James P. Kossin, a researcher with the National Oceanic and Atmospheric Administration.

He has looked at satellite images dating to 1979 and the total increase in 110-mph or higher windstorms has increased by about 8 percent a decade due to global warming, according to his study.

About the Author: