Evidence of Atlantic Multidecadal Oscillation in the magnetic properties of Alpine lakes during the last 2500Â years

- Rock-magnetic data from the Alpine region shows decadal climate variability.
- Spectral analysis indicates a coherent and significant periodicity of 50-60 years.
- Frequency-filtered signal co-varies with AMO instrumental record in last 110 years.
- AMO influence in the Alpine region extends back in time for at least two millennia.
- AMO influence is estimated ~ 0.4 °C on average but largely variable with time.

We re-analyzed rock-magnetic data of lake sediments from the Alpine region, which were previously recognized as sensitive climate proxy records, in search of decadal climate variability. Different methods of spectral analysis applied to the rock-magnetic data from two independent lake records show the presence of a coherent and statistically significant periodicity with a period of about 50-60 years. The frequency-filtered signal of this component co-varies with the instrumental record of the Atlantic Multidecadal Oscillation (AMO) over the last 110 years with a negligible phase shift. After having tested and ruled out the possible influence of solar irradiance in the putative AMO frequency band, based on spectral properties, we suggest that a significant influence of AMO in the Alpine region extends back in time for at least two millennia. Comparison of the amplitude of the AMO record with that of the Younger Dryas/Holocene transition suggests that AMO fluctuations played a significant role in pacing the past variability of the Alpine climate.