Ocean Temperature & Climate Oscillations
The Atlantic Multidecadal Oscillation, or AMO, describes long-term swings in North Atlantic sea-surface temperatures. These warm and cool phases can influence hurricane activity, rainfall, drought, marine ecosystems and climate variability over several decades.
What Is the Atlantic Multidecadal Oscillation?
The Atlantic Multidecadal Oscillation is a pattern of long-term sea-surface temperature variability across the North Atlantic Ocean. It is often discussed in terms of warmer and cooler phases that can last for decades.
The AMO is not a single storm, current or short-term weather event. It is a basin-scale climate signal that may reflect a mix of ocean circulation, atmospheric patterns, natural variability and long-term warming influences.
Quick Definition
The AMO is a multi-decade pattern of North Atlantic ocean temperature variability that can influence hurricanes, rainfall, drought and regional climate.
Warm and Cool AMO Phases
The AMO is usually described as alternating between a warm phase and a cool phase. These phases are based on broad North Atlantic sea-surface temperature patterns.
| AMO phase | North Atlantic signal | Typical influence |
|---|---|---|
| Warm phase | North Atlantic sea-surface temperatures are warmer than the long-term average | Can support more Atlantic hurricane activity and shift rainfall patterns |
| Cool phase | North Atlantic sea-surface temperatures are cooler than the long-term average | Can suppress some Atlantic hurricane conditions and alter regional climate patterns |
Why the AMO Matters
Rainfall and Drought
AMO phases can influence rainfall patterns around the Atlantic basin, including parts of North America, Europe, the Caribbean, West Africa and the Sahel.
Atlantic Hurricanes
Warmer North Atlantic waters can provide more favorable background conditions for tropical cyclone development when other ingredients, such as low wind shear and atmospheric moisture, are also present.
Marine Ecosystems
Long-term ocean temperature shifts can affect plankton, fish migration, fisheries and broader marine food webs across the North Atlantic.
European and North American Climate
North Atlantic temperature patterns can influence storm tracks, pressure systems and seasonal climate tendencies on both sides of the ocean.
Climate Interpretation
Because the AMO operates over multi-decade timescales, it can temporarily amplify or mask regional climate trends, making it important when interpreting long-term records.
AMO and Atlantic Hurricanes
The AMO is often mentioned in discussions of Atlantic hurricane cycles. During warm AMO-like periods, tropical Atlantic waters may be warmer, which can favor stronger or more numerous storms if atmospheric conditions cooperate.
However, the AMO does not “cause” hurricanes by itself. Hurricanes also depend on wind shear, humidity, atmospheric instability, pre-existing disturbances and ocean heat content.
Important
A warm AMO phase can increase hurricane-favorable background conditions, but it does not guarantee an active hurricane season.
AMO vs AMOC: What Is the Difference?
The AMO and AMOC sound similar, but they are not the same thing.
- AMO refers to multi-decade North Atlantic sea-surface temperature variability.
- AMOC refers to the Atlantic Meridional Overturning Circulation, a major system of ocean currents that moves heat through the Atlantic.
- AMO is a climate pattern or index.
- AMOC is a physical circulation system.
- The two may be related, but they should not be used as interchangeable terms.
How Is the AMO Monitored?
Scientists monitor AMO-like variability using sea-surface temperature records, ocean observations, climate indices, satellite data and statistical methods that separate regional variability from global warming trends.
- Sea-surface temperature anomalies: show warm and cool patterns across the North Atlantic.
- Climate indices: summarize long-term Atlantic temperature variability.
- Satellites: map surface temperature patterns over large ocean areas.
- Ocean buoys and ships: provide direct ocean measurements.
- Climate models: help test links between ocean variability, circulation and external forcing.
Common Misconceptions About the AMO
The AMO is not the Gulf Stream
The Gulf Stream is a major current. The AMO is a long-term temperature pattern across the North Atlantic.
The AMO is not the same as AMOC collapse
AMO variability may be related to Atlantic circulation, but it is not the same as an AMOC shutdown or collapse.
The AMO does not explain all Atlantic climate change
Long-term warming, aerosols, greenhouse gases, atmospheric circulation and natural variability all interact with Atlantic temperature patterns.
Frequently Asked Questions
What does AMO stand for?
AMO stands for Atlantic Multidecadal Oscillation, a long-term pattern of North Atlantic sea-surface temperature variability.
What is the Atlantic Multidecadal Oscillation?
The AMO is a multi-decade climate pattern involving warmer and cooler phases of North Atlantic sea-surface temperatures.
Does the AMO affect hurricanes?
Yes. Warm AMO-like periods can support more favorable Atlantic hurricane conditions, although hurricanes also require low wind shear, moisture and other atmospheric ingredients.
Is the AMO the same as the AMOC?
No. The AMO is a temperature variability pattern, while the AMOC is a major Atlantic ocean circulation system.
How long do AMO phases last?
AMO-like warm and cool phases can persist for several decades, although exact timing and interpretation vary depending on the dataset and method used.
