Southern Hemisphere orbital forcing and its effects on CO2 and tropical Pacific climate
K. Tachikawa1, A. Timmermann2, L. Vidal1, C. Sonzogni1, and O. E. Timm21Aix-Marseille Université, UMR7330, CNRS, IRD, CEREGE UM34, 13545 Aix en Provence, France 2IPRC, SOEST, University of Hawaii, Honolulu, HI 96822, USA
Received: 15 Mar 2013 – Accepted for review: 25 Mar 2013 – Discussion started: 05 Apr 2013
Abstract. The western Pacific warm pool (WPWP) is an important heat source for the atmospheric circulation and influences climate conditions worldwide. Understanding its sensitivity to past radiative perturbations may help better contextualize the magnitudes and patterns of current and projected tropical climate change. Here we present a new Mg/Ca-based sea surface temperature (SST) reconstruction over the past 400 kyr from the Bismarck Sea, off Papua New Guinea, along with results from a transient earth system model simulation. Our results document the primary influence of CO2 forcing on glacial/interglacial WPWP SSTs and secondary effects due to changes in wind-driven tropical boundary currents. In addition to the SST, deep ocean temperature reconstructions from this core are linked with Southern Ocean temperature and sea-ice variations on timescales of ~ 23 kyr. It is proposed that Southern Hemisphere insolation changes serve as pacemaker for sea-ice variations in the Southern Ocean, which in turn modulate windstress curl-driven upwelling of carbon-rich waters, hence controlling atmospheric CO2 and tropical WPWP temperatures.
Tachikawa, K., Timmermann, A., Vidal, L., Sonzogni, C., and Timm, O. E.: Southern Hemisphere orbital forcing and its effects on CO2 and tropical Pacific climate, Clim. Past Discuss., 9, 1869-1900, doi:10.5194/cpd-9-1869-2013, 2013.