A 2,000-year Bayesian NAO reconstruction from the Iberian Peninsula

Area of Science:

• Paleoclimatology
• Climate Dynamics
• Atmospheric Science

Background:

• The North Atlantic Oscillation (NAO) is a key driver of European winter climate, influencing temperature, precipitation, and storm tracks.
• Understanding past NAO variability is crucial for predicting future climate scenarios, yet decadal-scale reconstructions beyond the last millennium are limited.
• The spatial structure and climatic impacts of the NAO are not stationary, necessitating long-term reconstructions.

Purpose of the Study:

• To present a new 2,000-year proxy-based reconstruction of local NAO impact from the Iberian Peninsula.
• To investigate external forcings, specifically volcanic activity and solar activity, on NAO variability.
• To assess the stationarity of solar influence on the NAO across a latitudinal gradient.

Main Methods:

• A Bayesian approach was used to create a multi-annual, proxy-based reconstruction of local NAO impact.
• A lacustrine sedimentary archive from the Iberian Peninsula was utilized.
• External forcings (volcanic eruptions, solar activity) were assessed, and comparisons were made with existing NAO reconstructions.

Main Results:

• A 2,000-year reconstruction of local NAO impact with associated uncertainties was developed.
• A correlation was found between low sunspot numbers and low NAO values on a decadal scale.
• Inconclusive results were found regarding the impact of volcanic forcing on decadal NAO variability.

Conclusions:

• The study provides a novel, long-term NAO reconstruction from a previously underrepresented region (Iberian Peninsula).
• Solar activity appears to influence NAO variability on decadal scales, with low sunspot activity correlating with reduced NAO.
• Further research is needed to clarify the role of volcanic forcing and other modes of variability, like the East Atlantic pattern, on NAO non-stationarity.