Solar forced transient evolution of Pacific upper water thermal structure during the Holocene in an earth system model of intermediate complexity

Abstract

Forced by transient solar activities since 7 ka, the thermal structures of the Pacific upper water at boreal winter are featured by an enhanced response of 3-dimensional Western Pacific Warm Pool (WPWP) in an Earth system model of Intermediate Complexity at centennial scales. During solar maximum periods, the magnitude of surface ocean temperature variations is 30% larger in the western tropical Pacific than in the Niño3 region, while at subsurface, it is 40% larger in the subtropical North Pacific than in the western Equatorial Pacific. They compromise stronger zonal and meridional thermal gradients in surface and subsurface Pacific respectively which are both linearly responded to solar forcing at centennial periods. The surface gradient is most sensitive at 208-year period while the subsurface gradient shows more significance at periods longer than 208-year. Also noteworthy are two differences: (1) the phase lags at these periods of surface gradient are slightly smaller than that of subsurface; (2) the 148-year and 102-year periods in surface gradient are lost in subsurface gradient. These modeled features preliminary confirm the centennial fluctuations of WPWP in paleo-proxies and a potential solar forcing during the Holocene.