Eleven-year, 22-year and ~90-year solar cycles discovered in nitrate concentrations in a Dome Fuji (Antarctica) ice core

TL;DR

This study demonstrates that nitrate concentrations in Antarctic ice cores reflect solar activity cycles of approximately 11, 22, and 90 years, including periods of minimal sunspot activity, revealing new insights into solar variability over centuries.

Contribution

First to establish nitrate concentrations in ice cores as proxies for multiple solar cycles, including during grand minima, enhancing understanding of solar activity history.

Findings

Detected ~11, ~22, and ~90-year cycles in nitrate data

Nitrate variations reflect solar activity even during the Maunder Minimum

Supports cyclic behavior of the solar dynamo during grand minima

Abstract

Ice cores are known to yield information about astronomical phenomena as well as information about past climate. We report time series analyses of annually resolved nitrate variations in an ice core, drilled at the Dome Fuji station in East Antarctica, corresponding to the period from CE 1610 to 1904. Our analyses revealed clear evidence of ~11, ~22, and ~90 year periodicities, comparable to the respective periodicities of the well-known Schwabe, Hale, and Gleissberg solar cycles. Our results show for the first time that nitrate concentrations in an ice core can be used as a proxy for past solar activity on decadal to multidecadal time scales. Furthermore, 11-year and 22-year periodicities were detected in nitrate variations even during the Maunder Minimum (1645-1715), when sunspots were almost absent. This discovery may support cyclic behavior of the solar dynamo during the grand solar minimum.