Warming Pacific waters likely adding to Arctic sea ice loss, study finds

Sea ice floats in the Bering Strait off Cape Prince of Wales. (UAF photo by Gay Sheffield)

For the past decade, scientists have observed several years of abnormally low sea ice extent. While most of the cause has been attributed to a warming Arctic climate, a new study from the University of Alaska Fairbanks has found evidence that warming waters outside of the Arctic are impacting sea ice as well.

In the summer, there is a warm water mass that flows up from the Pacific Ocean through the Bering Strait across the Chukchi Sea. UAF marine science professor Harper Simmons says this transfer of warm water up into colder seas is normal.

“That flow is a natural state of the system,” Simmons said. “Unless things were really rearranged in the distant past.”

The water ends up resting in a layer just below the surface of the Arctic Ocean. Simmons says it stays there until the fall when colder water starts to form ice on the surface.

“That warm water makes its way slowly out of that layer and affects the ultimate amount of sea ice that forms in the Arctic,” Simmons said.

While that flow is normal, Simmons says there is emerging evidence that the warm water coming up from the Pacific is getting even warmer.

“Since the 90s, the temperature of that water has been observed to have a pretty significant warming trend,” Simmons said.

That trend translates to about half a degree Fahrenheit per decade. While that may not seem like a lot, Simmons says because it’s such a sudden change from years of stable sea ice conditions, it can be jarring to the system.

“If there was, in the past, kind of an expected sea ice formation of two meters of sea ice over the Beaufort,” Simmons said. “And this heat becomes part of that, then you would expect that instead of getting two meters of sea ice, you would only get a meter and a half of sea ice.”

R/V Sikuliaq docks in Nome (File photo by Emily Russell/KNOM).
The UAF-University of California San Diego study on warming Pacific waters was conducted on the R/V Sikuliaq, seen here docked in Nome. (Emily Russell/KNOM)

These observations were made as part of a study conducted by the University of Alaska Fairbanks and the University of California San Diego’s Scripps Institute of Oceanography. Simmons says the major change between this study and studies in the past was the introduction of new CTD, or conductivity, temperature and depth, technology.

The process works the same as how scientists had done it in the past. Basically, researchers lower a package into the ocean to monitor conditions in the water.

However, Simmons says the new custom-made CTD technology from the Scripps Institute exponentially increases the amount of data that researchers can gather.

“In a traditional cruise, you could make hundreds of profiles, and with a package like this, you could make thousands,” Simmons said.

Satellite imagery (upper figure) shows a warm jet of salty water flowing past Point Barrow then disappearing. Ship-based measurements (lower figures) show that the warm water subducts and continues below the surface. Lines A and B in the upper figure correlate with the ship-based data in the lower left and right figures, respectively. (Harper Simmons/UAF)

As scientists continue to monitor changes in sea ice, the impacts to the region continue to grow.

Diminishing ice has the potential to disrupt everything from marine mammal migration to the travel patterns of people who use the sea ice. Additionally, it could make travel across the Northwest Passage easier for shipping companies. Simmons says the diminishing sea ice could also impact the rate of coastal erosion.

“The more open water that you have for longer periods of time gives you more opportunities for storms to create large waves that increase coastal erosion.”

In the end, Simmons says that the findings of the study show that it isn’t just a warming Arctic that is leading to less sea ice.

“It’s not warmer temperatures locally,” Simmons said. “There’s this kind of global connection where warm water in the Pacific makes a difference.”

The study was published last month in the outlet Nature Communications.

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