Hurricane Helene: Climate change is making Florida's Big Bend more vulnerable to tropical threats
The topography of Florida's Gulf Coast makes it susceptible to storm surge.
Helene made landfall in Florida's Big Bend region Thursday night as a massive Category 4 hurricane -- the strongest hurricane to make landfall in the Big Bend on record.
The area, still reeling from Hurricane Idalia in 2022, is often in the bullseye of tropical storms forming in the Atlantic basin, experts told ABC News.
Why Florida's Big Bend is vulnerable to hurricanes
The Big Bend's proximity to the Gulf of Mexico puts the region directly in line to be impacted from tropical storm activity.
"We've seen the Gulf Coast, generally, as the target for many of the storms over the last four or five years," Marshall Shepherd, director of the Atmospheric Sciences Program at the University of Georgia and former president of the American Meteorological Society, told ABC News.
The underwater geology of the Gulf of Mexico leaves much of the low-lying coast unguarded against a massive influx of seawater. The continental shelf of the Florida Gulf Coast extends quite far offshore - up to 150 miles in some spots, according to the National Oceanographic and Atmospheric Administration (NOAA) - leaving the shallow waters nowhere to go.
The sheer radius of Helene is going to make the storm surge particularly problematic, because the additional water gets "shoved" onto the coast for an extended amount of time, Shepherd said.
Helene is forecast to bring a potentially life-threatening storm surge and dangerous coastal flooding along a wide swath of the Florida Gulf Coast. The storm surge is projected to rise to 20 feet high in the Big Bend area, forecasts show.
The Big Bend will also likely be hit by the eastern side of the storm, which typically carries the worst of the storm conditions and packs the strongest winds, Shepherd said.
"Stronger winds pile up more water, creating bigger storm surges," Michael Mann, a professor in the Department of Earth and Environmental Science at the University of Pennsylvania, told ABC News.
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Steering currents in the Gulf of Mexico in recent years may also have been directing some storms on similar paths through Florida from the Gulf of Mexico, Shepherd said.
In addition, extensive loss of seagrass may be contributing to increased flooding following heavy rainfall and strong storms, scientists say. The northeastern Gulf of Mexico contains the second-largest contiguous seagrass meadow in the continental U.S. but had lost about 15% of its area between 2001 and 2022, according to a study published last year in the journal Environmental Management.
How climate change is exacerbating the situation
Human-caused climate change is the primary cause for present-day rising sea levels, according to a consensus of climate scientists. It's also triggering more frequent and more intense extreme rainfall events, experts say.
While many factors contribute to the magnitude and impacts of storm surge and coastal flooding, average sea levels for many Gulf Coast communities are more than six inches higher today than they were just a few decades ago, data shows.
"We can't talk about Hurricane Helene without talking about climate change, which is causing stronger and more destructive storms," Mann said.
That sea level rise is also accelerating, research shows. Beginning in 2020, the overall U.S. coastline is projected to experience a sea level rise, on average, of about 11 inches through 2050, according to the federal government's Fifth National Climate Assessment, a breakdown of the latest in climate science, published in November. That amount of sea level rise previously took 100 years to reach (between 1920 and 2020).
During that same time period, the eastern Gulf Coast is projected to experience an average sea level rise of 8 to 12 inches, with even greater increases of 12 to 16 inches along the western Gulf Coast.
In addition to the sea level rise, heavy rainfall on top of existing storm surge will increase Hurricane Helene's coastal flooding impact along Florida's Gulf Coast, experts say.
Warmer than average sea surface temperatures are also likely having an impact on the storm.
Helene's path through the Northern Caribbean and Eastern Gulf of Mexico brought it across very warm ocean waters. Higher than normal sea surface temperatures in these regions were made at least 200 to 500 times more likely due to human-caused climate change, according to Climate Central's Climate Shift Index. Warm ocean waters provide the energy hurricanes need to form and intensify.
However, while a link has been established between the usually warm sea surface temperatures and human-caused climate change, it is not yet known to what degree that climate change may have influenced Hurricane Helene's development.
Research suggests that hurricanes are now intensifying more quickly. Warmer than normal oceans hold a lot of extra energy that these storms can feed on, and about 80% of major hurricanes, between Categories 3 and 5, undergo rapid intensification, defined as an increase in the maximum sustained winds of a tropical cyclone of about 35 mph or more in a 24-hour period.
Observational improvements and the natural variability of tropical cyclones, especially in the Atlantic Basin, in recent decades also play a role in the observed increase of rapid intensification events, according to NOAA. Hurricane Helene has fed on record levels of upper ocean heat content in the Gulf, favoring very rapid intensification, Mann said.
"Helene is a poster-child for the ways that human-caused climate change is amplifying the coastal threat from intensified hurricanes combined with rising sea levels," he added.
ABC News' Matthew Glasser and Daniel Peck contributed to this report.
