ENSO affects the North Atlantic Oscillation 1 year later.

Area of Science:

• Climate Science
• Atmospheric Science
• Oceanography

Background:

• El Niño-Southern Oscillation (ENSO) is a major driver of interannual climate variability.
• Simultaneous teleconnections between ENSO and extratropical climate are well-documented.
• The extratropical response to ENSO is typically studied for wintertime, simultaneous impacts.

Purpose of the Study:

• To investigate the 1-year lagged extratropical climate response to ENSO.
• To determine the strength and characteristics of these lagged teleconnections.
• To identify the underlying mechanisms driving the lagged ENSO response.

Main Methods:

• Analysis of observational climate data.
• Evaluation of climate model simulations.
• Investigation of atmospheric angular momentum anomalies.

Main Results:

• A robust 1-year lagged extratropical response to ENSO was identified in observations and models.
• This lagged response is comparable in strength to simultaneous ENSO teleconnections.
• The lagged response exhibits an opposite sign to the simultaneous response, impacting the North Atlantic Oscillation (NAO).
• Slowly migrating atmospheric angular momentum anomalies were found to explain the timing and sign of the lagged response.

Conclusions:

• Lagged ENSO teleconnections are a significant component of extratropical climate variability.
• These lagged effects have implications for understanding and predicting seasonal to interannual climate.
• The findings challenge existing notions of ENSO teleconnections and highlight the importance of delayed climate responses.