Old-growth CO2 flux measurements reveal high sensitivity to climate anomalies across seasonal, annual and decadal time scales

► The old-growth forest is a small net sink of carbon over 10 years but exhibits high interannual variability. ► FNEE is closely linked to climate perturbations resulting from major Pacific teleconnection events. ► Nearly 60 years of biometric FANPP data reveal long-term carbon trends associated with the PDO. ► Positive climate years lead to reduced carbon sink activity and increased respiration.