Quantcast
Environmental News for a Healthier Planet and Life

Help Support EcoWatch

Seals Reveal How Antarctic Sea Ice Melt Affects Ocean Currents

Climate
Seals Reveal How Antarctic Sea Ice Melt Affects Ocean Currents

By Tim Radford

Scientists have recruited the elephant seal—the bruiser of the pinniped world—to explore and report back on the dynamics of ocean currents in the Antarctic winter.

Elephant seal carrying satellite-linked sensor in Prydz Bay, Antarctica.University of Tasmania

And the mammals have delivered a potentially ominous message: because fresh water is melting from the sea ice, the density of southern ocean surface waters is significantly reduced.

If there is too dramatic a reduction, the all-important dense waters that descend to the depths and power the ocean conveyor system that drives circulation—and climate—could falter.

The southern elephant seal, Mirounga leonine, has been pressed into service as an all-weather submersible to investigate and record data from the polynya system—polynyas are patches of ocean, surrounded by shelf ice, that fail to freeze—of the southern ocean sea ice.

And the researchers report in Nature Communications journal that their study "highlights the susceptibility of Antarctic bottom water to increased freshwater input from the enhanced melting of the ice shelves, and ultimately the potential collapse of Antarctic bottom water formation in a warming climate."

The choice of elephant seals rather than humans is a simple one: shipboard research is all but impossible in the Antarctic winter.

Biologists had already enrolled the elephant seals—by sedating them, and gluing to their bulging necks a data monitor and radio transmitter that falls off with the next moulting season—to settle their own marine biological questions

So physicists and oceanographers have now taken advantage of the temperature and salinity data radioed back to them from each animal's 60 dives a day.

"We became very interested in the seal data once we saw they were foraging in the polynya regions, in particular the fact they were there through the winter, a critical period of time for dense shelf water formation, and a time that we really struggle to observe in any other way," said Guy Williams, a physical oceanographer at the University of Tasmania's Institute for Marine and Antarctic Studies.

Sea ice freezes as fresh water and rejects the salt into the water beneath it. This creates an insulating layer that cuts off the ocean from the freezing atmosphere, so sea ice never gets deeper than two meters.

But Dr Williams told Climate News Network:

"In polynyas, the surface of the ocean remains open, while the freezing continues, as newly-formed ice is swept away by persistent offshore winds. And certain topographic effects—coast, glacier tongues, icebergs—also help to keep the area open.

"Like a constantly emptied and refilled ice tray in the fridge, polynyas can generate up to 20 meters of sea ice growth in a winter, and, correspondingly, a much greater amount of salt rejection.

"It leads to this very important water mass called dense shelf water—dense enough once it escapes the continental shelf to mix all the way to the bottom of the ocean basins in the production of Antarctic bottom water."

This is the agency that drives the global ocean overturning system, a planetary-scale phenomenon, carrying heat around the globe and nutrients and dissolved atmospheric oxygen and carbon dioxide to deep layers of the ocean.

"Any reduction to Antarctic bottom water will slow the conveyor belt, and equally thin the conveyor belt, as the density, and depth to which it ultimately goes, decreases," Dr Williams said.

Coast Guard members work to clean an oil spill impacting Delaware beaches. U.S. Coast Guard District 5

Environmental officials and members of the U.S. Coast Guard are racing to clean up a mysterious oil spill that has spread to 11 miles of Delaware coastline.

Read More Show Less

EcoWatch Daily Newsletter

What happened to all that plastic you've put in the recycling bin over the years? Halfpoint / Getty Images

By Dr. Kate Raynes-Goldie

Of all the plastic we've ever produced, only 9% has been recycled. So what happened to all that plastic you've put in the recycling bin over the years?

Read More Show Less

Trending

Plain Naturals offers a wide variety of CBD products including oils, creams and gummies.

Plain Naturals is making waves in the CBD space with a new product line for retail customers looking for high potency CBD products at industry-low prices.

Read More Show Less
Donald Trump and Joe Biden arrive onstage for the final presidential debate at Belmont University in Nashville, Tennessee, on Oct. 22, 2020. JIM WATSON / AFP via Getty Images

Towards the end of the final presidential debate of the 2020 election season, the moderator asked both candidates how they would address both the climate crisis and job growth, leading to a nearly 12-minute discussion where Donald Trump did not acknowledge that the climate is changing and Joe Biden called the climate crisis an existential threat.

Read More Show Less
What will happen to all these batteries once they wear out? Ronny Hartmann / AFP / Getty Images

By Zheng Chen and Darren H. S. Tan

As concern mounts over the impacts of climate change, many experts are calling for greater use of electricity as a substitute for fossil fuels. Powered by advancements in battery technology, the number of plug-in hybrid and electric vehicles on U.S. roads is increasing. And utilities are generating a growing share of their power from renewable fuels, supported by large-scale battery storage systems.

Read More Show Less

Support Ecowatch