Late Holocene climate oscillations and solar fluctuations from speleothem STAL-AH-1, Sauerland, Germany: A numerical perspective

摘要

Initial C-14 activity in a late Holocene stalagmite (a C-14(stal)) from Attahohle (Sauerland, Germany) varies synchronously with atmospheric C-14 activity (a C-14(atm)). This observation provides independent chronological support for the correlation between a solar forcing proxy (atmospheric C-14 production rate, a C-14(prod)) and a climate proxy (delta O-18(stal)) in this stalagmite, and eliminates the need to 'tune' the chronology. Monte Carlo randomizations in which 100,000 synthetic delta O-18(stal) datasets were generated indicate that the correlation between a C-14(prod) and delta O-18(stal) is statistically robust. The absence of a significant time lag between a C-14(prod) and delta O-18(stal) implies rapid climate response at this site to variations in solar output. Positively correlated a C-14(prod)-delta O-18(stal) indicates drier winter conditions during late Holocene solar minima. This supports atmospheric amplification models that predict reduced NAO indices during solar minima if kinetic enrichment of delta O-18 during dry phases outweighs the reduction of delta O-18 in rainfall that results from lower air temperatures during negative NAO phases.