They are as unique as human fingerprints!
Just as human fingerprints are unique to an individual, strong storms can leave a distinct signature in the form of ripples on the seafloor. These signatures are known as ripple bedforms, and they are formed when waves generate currents that oscillate back and forth on the ocean floor, stirring up sand and sediment.
According to Carter DuVal, a University of Delaware doctoral student studying oceanography and lead author of the paper recently published in the journal Continental Shelf Research, being able to measure and explain these ripples will not only help scientists understand storms that have already happened, but will also help scientists model and predict how future storms might behave.
Currently, models predict that when a storm begins to weaken, the ripples will reduce in size due to smaller waves. However, using the fingerprint algorithm and analyzing data from Hurricane Sandy (2012) at Redbird Reef, the team revealed that the ripples actually froze at the size generated during the height of the storm.
Redbird Reef is an artificial reef located in the Atlantic ocean about 16 miles off the coast of Delaware’s Indian River Inlet. The man-made structure encompasses old subway cars, tugboats, tires, and military tract vehicles, providing a home for marine organisms.
The researchers placed sensors at the reef before Hurricane Sandy’s arrival to measure the waves, currents, and sand formations on the seafloor. During Sandy’s peak, the sensors detected waves over 24 feet high and currents racing back-and-forth across the seafloor at 5.2 feet per second.
"So not only were we seeing a record of the storm, but of the most energetic part of the storm. This is very important for recording the storm's dynamics," said DuVal in a UD news release.
DuVal explained that the fingerprint algorithm can also be used to help researchers understand how the ripples change over time. For example, one month after Hurricane Sandy, many of the smaller ripples had disappeared, and larger ripples had been smoothed out into what are called “relic ripples.”
"Relic ripples that are left behind can become the starting point for the next storm, or because they are somewhat rigid, they may slow down future storms," said Art Trembanis, associate professor of oceanography in UD's College of Earth, Ocean, and Environment, in the release.
The team also created a 3D printed model of a portion of the reef (seen in the image below) using data from after Sandy. "It gives you a perspective that you cannot get by looking at a two- or three-dimensional map on a screen," said DuVal. "Not only can we look at the surface, but also the texture too.
Evan Krape/ University of Delaware
According to the United States Environmental Protection Agency, increased greenhouse gas emissions are expected to "increase the frequency, intensity and/or duration of extreme events." Luckily, these ripples could reveal insights into these unpredictable and future extreme weather patterns.