Is the Atlantic Shifting Gears?

Tracking the Potential AMO Flip

Fred Pickhardt Mar 29

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For the first time in over 30 years, we are seeing evidence that the Atlantic Multidecadal Oscillation (AMO) might be heading into its negative (cool) phase. If this shift is real, it could fundamentally change our weather patterns for the next two decades.

The “Horseshoe” Emerges

The hallmark of a negative AMO is a distinct “C-shaped” or horseshoe pattern of cool water stretching across the North Atlantic. Looking at current sea surface temperature (SST) anomalies, we are seeing exactly that: a crescent of cooler water running from the UK down to the Canary Islands, paired with a persistent cold pool south of Greenland.

The cold “blob” south of Greenland is particularly telling. It’s often noted as a byproduct of a slowing AMOC (the ocean’s “conveyor belt”) and is also closely linked to a negative phase of the Atlantic Multidecadal Oscillation (AMO).

North Atlantic SST Anomaly (topicaltidbits.com)

A Cooling Tropical Atlantic

The biggest hurdle for a negative AMO phase recently has been the Atlantic Main Development Region (MDR). In recent years, the tropics have remained stubbornly warm. However, as of March 2026, we are seeing widespread neutral to cool anomalies in the MDR. This makes the case for a phase shift significantly stronger than it was just twelve months ago.

Atlantic MDR SST Anomaly (Tropicaltidbits.com)

Real Shift or False Start?

The AMO is a marathon, not a sprint. History is full of “false starts” where the ocean cools for a year or two before the warm cycle resumes. Current cooling in the eastern Atlantic could simply be a temporary reaction to atmospheric triggers, like a strong Positive North Atlantic Oscillation (NAO) phase. To confirm a true regime shift, these cool anomalies need to persist and expand for several consecutive years. We aren’t ready to declare the “Warm Era” over just yet, but the needle is moving.

What This Means for the Future

If this pattern holds through the 2026 hurricane season and into 2027, the implications are significant. A sustained negative AMO phase typically brings:

• Quieter Hurricane Seasons: Cooler water in the MDR means less fuel for storms and generally higher wind shear, which rips systems apart.
• Rainfall Shifts: We could see a return to drier conditions in the African Sahel.
• European Weather: A shifting jet stream often translates to cooler, wetter summers for parts of Europe.

We are watching the Atlantic closely. If the 1995–2025 warm cycle is indeed ending, the next 20 years of weather will look different from the last.

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© 2026 Fred Pickhardt
548 Market Street PMB 72296, San Francisco, CA 94104
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