Solar Activity and Summer Wind Regimes for the Past 9500 Years as Inferred by Diatoms in Lake Du Sommet, Southern Quebec, CA

Gridded correlation analyses revealed that diatom flux, diatom inferred circulation, observed June wind velocity, the June NAO index, and observed solar activity are significantly linked to higher June 500hPa geopotential heights in the southern North Atlantic and lower 500hPa heights in northern Quebec. During the Holocene, diatom production, species composition and the diatom inferred circulation of the water column of Lac du Sommet, a small lake in southern Quebec, were all strongly related. A high resolution study of the past 40 years showed that diatom production of this lake varies according to observed wind and solar activity. The 9500 year diatom record shows 930 and 2100-year periodicities, previously observed in independent solar proxy records. During the past 9000 years, solar activity explained 40% of the overall diatom changes, diatom production and diatom-inferred lake circulation, and 46% of the variance in the dominant diatom taxon Fragilaria virescens. Our results suggest that solar activity intensified the south-north pressure gradient and led to increased June wind activity in southern Quebec. Higher wind activities were inferred from 5000 to 4000 cal BP, 3000 to 1500 cal BP, and for the past 100 years.