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Atlantic waters affect Arctic Ocean more than previously known

The abnormal flow of warm Atlantic Ocean waters and marine life into the Arctic Ocean is occurring in polar regions previously thought to be unaffected by the phenomenon. 

According to a new study co-authored by several researchers at the University of �������� Fairbanks’ International Arctic Research Center, the flow is now affecting the Amerasian Basin, the larger of the Arctic Ocean’s two major basins. The region includes the waters extending northward from eastern Siberia, ��������, Canada and western Greenland.

The study, published today in the journal Science Advances, describes how the processes related to the abnormal flow — called Atlantification — can affect the Arctic climate. 

“Several decades ago, scientists were simulating the global climate using global models without the Arctic Ocean because they thought that the Arctic is too small to have a significant impact on Earth’s climate,” said Igor Polyakov, the study’s lead author and a physical oceanographer with IARC. “Nowadays, there is a lot of attention here. It is absolutely impossible to understand the Earth’s heat balance without the Arctic.”

According to Polyakov, the continued Atlantification of Arctic waters will fundamentally change heat and energy fluctuations both regionally and at broader geographical scales. Impacts include further loss of Arctic sea ice, weakening of the salinity gradient in the Arctic Ocean’s upper water layers and accelerated warming of the atmosphere and ocean. 

The researchers’ observations are based on data collected by instruments moored in the Arctic Ocean. The data show that global climate models, which already predict atmospheric and oceanic warming and a future loss of sea ice, haven’t fully accounted for Atlantification, Polyakov said. 

“There is a discrepancy between the climate models and our in-ocean observations,” Polyakov said. “We need to improve models in order to be more reliable in simulating Atlantification, because it’s an important component of climate change in the Arctic, impacting the state of the ocean, sea ice, air-sea interactions and ecosystems.”

A rapidly changing halocline

In the Arctic Ocean, stratification — the vertical layering of water with different temperatures, salinities and densities — affects the formation and retention of sea ice. 

When stratification is strong and stable, the warmer waters that naturally flow into the Arctic Ocean from lower latitudes stay at greater depths and don’t mix with the surface fresh layer. 

As recently as 15 years ago, stratification remained strong. But that’s changing.

The mixing layer between colder, fresher and less dense surface water and the warmer, saltier and denser water below is called the halocline. Between 2002 and 2023, researchers observed that the halocline moved closer to the surface in the Eurasian Basin, the Arctic Ocean’s second-largest basin, which lies north of eastern Greenland, Svalbard, Franz Josef Land and  Severnaya Zemlya.

Now, the researchers’ observational records demonstrate that Atlantification has progressed beyond the Lomonosov Ridge, into the Amerasian Basin north of the New Siberian Islands and central Siberia. 

Combined with warmer Arctic air temperatures, Polyakov said, the weakening of the halocline associated with Atlantification drives a positive feedback loop: Less sea ice is forming in the winter, and more is melting in the summer. 

In the easternmost part of the Siberian Arctic, close to ��������, stratification is still strong, the researchers found.

Moorings tell us more

Data from the study came from ocean moorings deployed on the Siberian Arctic’s continental slope by the , a multinational program.  Moorings outfitted with a variety of instruments are anchored to the ocean bottom and extend upward. They continuously record oceanic parameters, including temperature, salinity and flow rates. Some moorings have been maintained at the same positions for more than two decades. 

The instruments weren’t the only devices recording change. The naked eye also could observe the declining thickness and abundance of sea ice in the Siberian Arctic during the study years, Polyakov said. He will lead a new expedition to the Arctic this coming summer.

“For the greatest evidence of climate change over the past few decades, look no further than the Arctic,” he said.

ADDITIONAL CONTACT: Igor Polyakov, ipolyakov@alaska.edu, 907-474-2686

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