Scientists found that ‘rivers in the sky’ are triggering ocean heatwaves in the North Pacific and North Atlantic, but their effect changes with the seasons

If you were anywhere near the US West Coast in early 2023, you likely remember the constant storms. Nine atmospheric rivers, massive airborne corridors of moisture often dubbed ‘rivers in the sky,’ struck California back to back in just three weeks, causing over $3 billion in damage, flooding cities, and toppling power lines. It was dramatic, it was visible, it was headline news everywhere.

But very few were talking about what those same atmospheric rivers were doing quietly beneath the surface of the ocean.

In a new study published in Nature Communications, researchers Suqiong Hu and Shineng Hu at Duke University have identified a missing link: atmospheric rivers (ARs) are contributing significantly to the development of marine heatwaves (MHWs) in the North Pacific and North Atlantic. And that’s big news if you’ve been following what marine heatwaves are doing to American fisheries and coastal economies.


So what exactly is going on out there?
Think of the surface of the ocean as a frying pan. Normally, some heat flows prevent it from getting too hot. But when an atmospheric river passes overhead, it throws that balance off through a number of competing mechanisms.

On the one hand, the heavy cloud cover that comes with an AR has a cooling effect by keeping sunlight from reaching the ocean. At the same time, the AR provides the same warm, humid air that does two warming things: it reduces the amount of heat lost by the ocean through turbulent latent and sensible heat fluxes, and it traps additional heat through the enhanced greenhouse effects of additional water vapor and clouds, thereby reducing outgoing longwave radiation. In winter, these warming effects dominate, and the ocean warms throughout the basin. The summer picture is more complex, with a horseshoe-shaped anomaly over the North Pacific, where some areas warm and others cool, depending on the strength of the turbulent warming effect relative to solar cooling.

The researchers found that these signals driven by atmospheric rivers appear in satellite data more than a week before a marine heatwave reaches its peak, with the strongest atmospheric river activity occurring about two days before the ocean gets its hottest. ARs are not mere bystanders. They are helping push ocean temperatures over the edge.

Why should Americans care?
Because marine heatwaves are not an abstract science problem. They hit close to home, literally.

NOAA is currently tracking a massive marine heatwave off the US West Coast in 2026, comparable to “The Blob,” the infamous 2013-2016 ocean warming event that disrupted Pacific ecosystems. On September 9, 2025, the northeast Pacific hit its highest average temperature ever: 20.6 degrees Celsius (about 69°F).

The last time something like The Blob happened, it was serious. A 2023 study in Fish and Fisheries, ‘Impact of the 2014–2016 Marine Heatwave on US and Canada West Coast Fisheries,’ found the heatwave triggered an unprecedented harmful algal bloom that shut down shellfish fisheries coastwide and cost an estimated $22 million in tourism revenues in Oregon and Washington alone. The California Dungeness crab industry needs $25.8 million in federal relief appropriation. Record numbers of humpback whales became entangled in crab trap lines. The kelp forests were gone, and so were the fisheries for abalone and urchin.

That was one heatwave. Scientists say such events are happening more often and with higher intensity.

The hidden connection your weather app won't show you
What makes the Duke University study especially significant is that it identifies atmospheric rivers, a weather phenomenon already experienced by millions of Americans, as a key, previously unstudied trigger for ocean extremes.

A 2023 study published in Communications Earth & Environment, “Arctic Warming Contributes to Increase in North-east Pacific Marine Heatwave Days Over the Past Decades,” found that the frequency and duration of marine heatwaves has been on the rise along with ocean warming caused by climate change. The North-east Pacific is one of the places where this is especially true. The new Duke research adds another layer: it's not just slow background warming that does the damage. Short-lived atmospheric events, like ARs, can tip the scales on a week-to-week basis, accelerating when and where marine heatwaves erupt.

The study examined satellite and reanalysis data from 1982 to 2023 and verified the results across 15 separate climate models. The AR signature before the peaks of marine heatwaves was uniform across more than 70% of these models, providing a robust indication that this is not a statistical fluke.

What this means going forward
The research is not just about the past. It opens doors for better prediction.

If scientists can track atmospheric rivers, they might be able to predict marine heatwaves days in advance. That could provide fishermen, coastal managers and ecosystem scientists with a vital head start.

And then there’s the long-term picture. With climate change, atmospheric rivers are anticipated to shift poleward and intensify. If ARs are already contributing to the onset of marine heatwaves, then a future with more frequent, more intense ARs could bring increasingly severe ocean heat events to American coasts.

The researchers also note a possible two-way street: marine heatwaves may, in turn, strengthen or redirect atmospheric rivers. It turns out that the ocean and the atmosphere are in constant conversation. We're only just beginning to learn the language.