Sharks turned into storm trackers to predict hurricane intensity: Know how scientists are using it

Researchers in the US have turned the killer shark into mobile near-real-time ocean-data observers using CTD tags to understand the potential intensity of a hurricane before it makes landfall. The testing is being done by researchers at the University of Delaware in order to measure ocean conditions to inform oceanographic, atmospheric and climate models.

CTD tags are compact electronic devices that record ocean electrical conductivity, a measure closely linked to salinity, along with temperature and depth, as the marine animals carrying them swim and dive. "Animal-borne sensors have been used successfully by oceanographers for years, particularly on elephant seals in polar regions where scientific observations are scarce," said Aaron Carlisle, principal investigator ​and a professor in the university's School of Marine Science and Policy.

Carlisle noted that sharks present a valuable new avenue for this kind of research, since they are plentiful, widely spread across the ocean, and more accessible than many protected marine mammals. Until now, shark tagging has mainly been used to track their movement patterns and habitat use.

Hurricane research

Researchers at the University of Delaware chose sharks capable of gathering data most relevant to hurricane research, prioritising species that surface frequently enough for their tags to relay information to satellites. Earlier studies identified shortfin mako sharks, blue sharks, smooth hammerheads, and juvenile great white sharks as promising candidates for such research in the North Atlantic.

"We are really most interested in the heat content of the top layer of the ocean, which is known as the mixed layer," Carlisle said. "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," Carlisle added.

"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," Carlisle further added.

Caroline Wiernicki, a University of Delaware doctoral candidate in marine science, stated that this process started in early May, when highly migratory species came closer to the coast from their winter habitats further out in the ​Atlantic. Wiernicki added that researchers moved 30 to 40 miles (50 to 65 km) offshore aboard a research vessel, deployed baited lines and waited, typically ‌two to three ⁠hours, for a shark to take the bait.