Solar forcing of Holocene droughts in a stalagmite record from West Virginia in east-central North America

Elevated Sr/Ca ratios and δ¹³C values in Holocene-age stalagmite BCC-002 from east-central North America record six centennial-scale droughts during the last five North Atlantic Ocean ice-rafted debris (IRD) episodes, previously ascribed to solar irradiance minima. Spectral and cross-spectral analyses of the multi-decadal resolution Sr/Ca and δ¹³C time series yield coherent ∼200 and ∼500 years periodicities. The former is consistent with the de Vries solar irradiance cycle. Cross-spectral analysis of the Sr/Ca and IRD time series yields coherent periodicities of 715- and 455-years, which are harmonics of the 1,450±500 year IRD periodicity. These coherencies corroborate strong visual correlations and provide convincing evidence for solar forcing of east-central North American droughts and strengthen the case for solar modulation of mid-continent climates. Moisture transport across North America may have lessened during droughts because of weakened north-south temperature and pressure gradients caused by cooling of the tropical Pacific and Atlantic Oceans.