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Instruments on migrating elephant seals measure deep warm water anomalies lasting much longer than surface warming – ScienceDaily


The North Pacific Heat Wave, a marine heat wave that began in late 2013 and continued into 2015, was the largest and longest marine heat wave on record. A new study using data collected by elephant seals shows that in addition to the well-documented surface warming, the deeper warm water anomalies associated with the Blob were much more extensive than previously reported.

The new discoveries were reported by a group of biologists and oceanographers from the University of California in Santa Cruz in a article published July 4 in the Journal of Geophysical Research: Oceans.

“Elephant seals are collecting data in places other than existing oceanographic platforms,” ​​explained senior author Christopher Edwards, a professor of ocean sciences at the University of California, Santa Cruz. “This is an underutilized dataset that can inform us about important oceanographic processes and also help biologists understand the ecology of northern elephant seals.”

For decades, UCSC elephant seal researchers, led by co-author Daniel Costa, professor of ecology and evolutionary biology and director of UCSC’s Institute of Marine Sciences (IMS), have used advanced tagging technology to track the months-long migrations of elephant seals in the North Pacific.

“While seals have been used to study the physical oceanography of polar regions for some time, this is one of the first studies to use data collected by seals to address physical oceanographic questions in temperate regions such as the North Pacific.” said Costa. .

The animals’ sensors record depth, temperature and salinity as the animals repeatedly dive to great depths during their nearly 6,000-mile migration across the North Pacific.

“Female elephant seals go out into the open ocean where a ship can go and collect data only occasionally, whereas we have elephant seals collecting data everywhere,” said first author and IMS biologist Rachel Holser. “It’s unusual to have this kind of data with the resolution we have in both time and space, and at depths below a few hundred meters.”

Elephant seal data collected during the Blob showed that the abnormally high temperature extended 1,000 meters (3,280 feet) below the surface. Subsurface warming continued in 2017, well after surface temperatures had returned to normal levels.

The Blob has been well-studied in relation to surface warming, which has been driven by atmospheric conditions and has been declining since the end of 2015. The widespread underground warming raises questions about the mechanisms underlying it, Edwards said.

“These temperature anomalies are so deep that it is unlikely to be due to mixing from the surface,” he said. “One plausible mechanism is that unusually warm water was carried north from further south. What we don’t yet know is whether this northward transport is directly or indirectly related to surface warming. Changes at the surface could temporarily change the deep currents to pull southern waters northward.”

Marine heat waves are expected to increase in frequency, magnitude and duration as global temperatures continue to rise. These events can have significant impacts on marine life, as well as economic consequences for local communities that depend on marine fisheries and ecosystems. Understanding the physical processes associated with marine heat waves will help scientists predict their onset and development, and enable people to anticipate and address environmental and economic impacts.

“Just as with land-based heat waves, we’ve seen a dramatic increase in the frequency and magnitude of marine heat waves over the past decade,” Holser said. “The more information we can collect, the better we can understand what’s going on and solve the problems. This study shows the value of working with elephant seals to collect oceanographic data that complements other methods.”

In addition to Holser, Edwards, and Cost, ocean science graduate student Teresa Keats also contributed to the study and is a co-author of the paper. This work was supported by the US Office of Naval Research and the Central and Northern California Ocean Observing System (CeNCOOS). With continued support from CeNCOOS, Costa’s lab, in collaboration with Edwards and Professor of Ocean Sciences Rafael Cudel, continues to collect oceanographic data using elephant seals.

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Materials is provided University of California – Santa Cruz. Originally written by Tim Stevens. Note: Content can be edited for style and length.

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