University of Delaware researchers are attaching satellite sensors to migratory sharks along the U.S. East Coast to measure ocean depth, temperature, and electrical conductivity, gathering real-time subsurface data that can help climate models better predict hurricane intensity and coastal storm impacts before landfall.
From cinematic creature features to popular weather-disaster films, sharks have long held a fearsome reputation in popular culture. But off the U.S. East Coast, marine predators are quietly taking on a very different job description. Researchers are deploying advanced electronic tags on migratory sharks to collect critical oceanographic data from areas that traditional weather instruments struggle to reach.
How Sharks Collect Critical Ocean Data
The project relies on compact electronic devices known as Conductivity, Temperature, and Depth tags. These instruments measure water temperature, depth, and electrical conductivity—a metric closely related to salinity—as marine animals swim through the water column. Aaron Carlisle, principal investigator and a professor in the University of Delaware’s School of Marine Science and Policy, noted that animal-borne sensors have been used successfully by oceanographers for years, particularly on elephant seals in polar regions where scientific observations are scarce
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Sharks offer a distinct advantage over marine mammals because they are abundant, widely distributed, and easier to access. Researchers select specific species that undertake long migrations and surface frequently enough to transmit their readings via satellite. In the North Atlantic, target species include shortfin mako sharks, blue sharks, smooth hammerheads, and juvenile great white sharks.
“The tags are attached to the dorsal fin. Then every time the shark fins (swims) at the surface, the tag can communicate and transmit data to the orbiting network of satellite receivers.”
Aaron Carlisle, principal investigator and professor at the University of Delaware
Fieldwork begins in early May as these highly migratory animals move closer to the coast from their winter habitats further out in the Atlantic. According to Caroline Wiernicki, a University of Delaware doctoral candidate in marine science, researchers travel 30 to 40 miles offshore aboard a research vessel, deploy baited lines, and wait roughly two to three hours for a shark to take the bait.
Targeting the Mixed Layer to Forecast Hurricanes
The primary motivation behind the tagging initiative is improving hurricane forecasting. Atmospheric and climate models require accurate measurements of ocean heat content to predict how powerful a storm will become before it reaches land.
“We are really most interested in the heat content of the top layer of the ocean, which is known as the mixed layer. This is the part of the water column that really drives hurricane intensity — warmer mixed layer equals stronger hurricane — as it holds the heat that feeds hurricanes.”
Aaron Carlisle, principal investigator and professor at the University of Delaware
Capturing data in the Northwest Atlantic presents severe challenges. The Gulf Stream shifts often, spinning off eddies and creating complex boundaries where shallow coastal shelf waters meet the deep ocean. Satellites cannot see below clouds, and traditional Argo floats often avoid turbulent zones.
Marine predators naturally gravitate toward these dynamic ocean fronts and eddies in search of food. As Ben Kirtman, an atmospheric scientist at the University of Miami’s Rosenstiel School and lead scientist of NOAA’s North American Multi-Model Ensemble system, explained, Marine predators like sharks naturally seek out dynamic ocean features such as fronts and eddies. These are areas where models often lack sufficient observations
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Scaling Up Tagging Technology and Field Operations
Recent deployments demonstrate the sheer volume of data these animals can generate. Off the coast of Cape Cod in 2021, researchers tagged 18 blue sharks and one shortfin mako, equipping each with a satellite sensor designed to record depth and temperature. Over time, those sharks delivered more than 8,200 profiles encompassing nearly 59,000 individual measurements, with some dives reaching almost 2,000 meters into cold, deep waters.
Neil Hammerschlag, a co-author of a related study and executive director of the Shark Research Foundation, emphasized that repurposing a more advanced tag capable of transmitting location data along with temperature and depth information
was essential for linking subsurface ocean conditions directly to specific geographic locations.
On the vessel, the handling process moves rapidly. Carlisle described the procedure as operating like a pit crew
in an auto race, with physical tagging taking under five minutes. Teams follow strict animal care guidelines, attaching tags with materials designed to corrode and fall away over time. Every shark undergoes a health check before release to ensure normal behavior and prevent data bias.
Measurable Improvements in Climate and Weather Models
When researchers integrated shark-collected observations into the Community Climate System Model version 4, running forecasts alongside standard data, the results showed substantial gains in accuracy. In coastal and slope regions, temperature prediction errors dropped by up to 40 percent. On the continental shelf, errors decreased by more than one degree Celsius during certain months.
Laura H. McDonnell, the study’s lead author and now a postdoctoral investigator at the Woods Hole Oceanographic Institution, stated that tagged marine predators can provide complementary in-situ observations at the surface and at depth
to fill vital gaps left by conventional systems.
During the study period, sharks collected about 90 percent more profiles in the target area than standard Argo floats. The resulting improvements in climate models did not fade quickly; the new data helped guide models onto a more stable trajectory from the start, yielding better consistency over months of forecasting.
Coastal Resilience and Future Outlook
If the ongoing research continues to prove successful, the stream of real-time data could fundamentally upgrade hurricane intensity forecasts along the U.S. East Coast. Wiernicki noted that more reliable tracking gives communities stretching from North Carolina to Massachusetts better tools to increase coastal resilience against strengthening storms.
Skeptics may recall Amity Island or fictional vortex films, but researchers stress that the reality is far more routine. Wiernicki likened the tagged animals to everyday workers, noting that encountering a data-collecting shark is more like Bob from Accounting, clocking in with the day’s temperature profiles before he heads back out
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