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Changing winds could amplify North Atlantic climate anomaly

As the planet's oceans are gradually warmed by the effects of climate change, a huge area in the North Atlantic stands out as an unusual zone of relative cooling.

A region that stretches roughly from Greenland to Ireland, counterintuitively dubbed the North Atlantic warming hole, is a conspicuous patch of blue on global climate change maps. Researchers say its temperature contrast could intensify in the decades ahead as shifting climate-driven winds amplify the cooling process in the North Atlantic.

A new study, in the Journal of Climate, projects that wind-driven changes in ocean circulation would begin adding to the cooling effect in the region by about 2040.

"Even though there's global warming, it's an area that's cooling, and it's expected to continue to cool," said Kay McMonigal, an assistant professor at the University of Alaska Fairbanks College of Fisheries and Ocean Sciences and lead author of the study.

Scientists are still working to fully understand why the relative cooling in the North Atlantic warming hole is happening, but global circulation patterns are considered a key ingredient. That led researchers to use computer modeling to create two scenarios: one in which changing winds affect ocean circulation, and one in which they don't.

Those models, which incorporate a moderate-high scenario for future greenhouse gas emissions, indicate that the North Atlantic warming hole won't immediately be affected by wind-driven ocean circulation changes. That changes by about 2040, with weaker winds contributing to added cooling in the region for several decades.

Lighter winds would reduce stirring in the ocean between Newfoundland and Greenland, diminishing the amount of warm subsurface water being mixed upward. Large-scale ocean circulation would then spread that cooling signal to the wider region.

Temperature shifts in the North Atlantic warming hole are an important ingredient in future climate change, with the potential to significantly affect precipitation levels and temperatures throughout the broader region. Because of that outsized role in climate impacts, a clearer understanding of the dynamics that could sustain or intensify the warming hole are important for building accurate models.

"There are a lot of implications for weather, especially over Europe," McMonigal said. "If we want to be able to predict things well, the winds need to be accounted for."

Other contributors to the study include Melissa Gervais, an associate professor at Pennsylvania State University, and Sarah Larson, an associate professor at North Carolina State University.