Hurricanes Pack a Bigger Punch for Florida’s West Coast
Boulder, Colo., USA: Hurricanes, the United States’
deadliest and most destructive
weather disasters, are notoriously difficult to predict. With the average
storm intensity as well as the proportion of storms that reach category 4
likely to increase, more accurate predictions of future hurricane impacts could help
emergency officials and coastal populations better prepare for such
storms — and ultimately, save lives.
Such predictions rely on historical records that reveal cyclic changes,
such as the El Niño–Southern Oscillation, that can affect hurricane
frequency. But the short observational records that exist for many regions,
including Florida’s East Coast, are inadequate for detecting climate
patterns that fluctuate over longer timeframes.
new research presented Wednesday at the annual meeting of The Geological Society of
America is extending Florida’s hurricane record thousands of years back in
time—and hinting at a surprise finding.
“There has been little to no research done on the hurricane record for
Florida’s East Coast,” explains Ilexxis Morales, a graduate student in the
Environmental Science program at Florida Gulf Coast University and the
study’s lead author. “The national hurricane database for this area
currently only extends back to the 1850s,” she says.
But what that record suggests, says Morales, is quite intriguing,
especially with respect to intense (category 3–5) storms. “It 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,” she says.
To better understand this discrepancy, Morales and her Florida Gulf Coast
University 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. Their analysis shows that in
contrast to the dark organic matter that comprises most of the cores,
hurricanes leave behind a coarser deposit distinctive enough to be called a
“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 muds, the researchers can detect ancient tempest deposits
using simple grain-size analyses.
After identifying the tempest deposits (called tempestites), the team used
a variety of methods, including a Lead-210 germanium detector and
radiocarbon dating, to determine their ages. While still preliminary, the
results from the seven cores the researchers have analyzed to date suggest
that there are fewer visible tempestites in the East Coast cores 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. Morales
speculates this difference could be due to the shifting position of the
Bermuda High, a semi-permanent ridge of high pressure that can affect a
hurricane’s direction. “When the Bermuda High is in a more northeasterly
position, hurricanes tend to track along Florida’s East Coast and up to the
Carolinas,” says Morales. “When it shifts southwestward towards the U.S.,
the high tends to push storms into the Gulf of Mexico instead.” Sea-surface
temperatures can also help explain the difference, says Morales. “Normally
the Atlantic is colder than the Gulf, and this colder water makes it harder
for hurricanes to sustain their strength,” she explains.
Similar “paleotempestology” studies have been conducted in other locations
that are also susceptible to hurricanes, including Texas, Louisiana, New
England, and even Australia, and the results have a number of practical
applications. “This data will go to the national hurricane database, which
will then help meteorologists better predict storm paths,” Morales says.
The data will also help show which areas are more susceptible to hurricane
damage, enabling insurance companies to better adjust hurricane-insurance
rates and developers to select building sites less susceptible to storm
Once complete, says study co-author James Javaruski, the longer storm
record could help researchers determine whether changes observed in it can
be attributed to human-induced climate change. The findings can also offer
insight into what could happen in the future. “If we see in other studies
that sea surface temperatures were increasing over a certain time frame and
find that hurricanes also increased over that same time frame,” Javaruski
says, “it can give us a good idea of what to expect as we artificially
raise sea surface temperatures now.”
Paleotempestology of the East Coast of Florida
Wednesday, 28 Oct., 11:20 a.m.
Florida Gulf Coast University
Fort Myers, Florida
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The Geological Society of America, founded in 1888, is a scientific society
with members from academia, government, and industry in more than 100
countries. Through its meetings, publications, and programs, GSA enhances
the professional growth of its members and promotes the geosciences in the
service of humankind. Headquartered in Boulder, Colorado, USA, GSA
encourages cooperative research among earth, life, planetary, and social
scientists, fosters public dialogue on geoscience issues, and supports all
levels of earth science education.