Middle Miocene-Pliocene Sea Surface Temperatures: The TEX86 Perspective

Abstract:

Proxy records of sea surface temperature (SST) are essential to understanding the dynamics of the Pliocene warm period, though different approaches have given offset and sometimes decoupled results. Recent work (Zhang et al. 2014; O’Brien et al. 2014) presents TEX₈₆ derived SSTs that show higher temperatures in the Pacific warm pool of the early Pliocene compared to Uk’37 and Mg/Ca SST records. While TEX86 is subject to several limitations, include a relatively large calibration error and an uncertain depth of production, the data suggest that a strong zonal temperature gradient in the equatorial Pacific was maintained in the hotter world of the early Pliocene in contrast to previous work. Here we present preliminary, low-resolution TEX86 data from 30 sites with previously published Uk’37 or Mg/Ca records from the Pacific, Atlantic and Indian Oceans. The interval from 16 Ma to 2 Ma is targeted to capture the transition from the hothouse of the Middle Miocene Climatic Optimum to the icehouse of the late Pliocene. Both zonal and meridional SST gradients are evaluated and the three temperature proxies are compared to investigate when and in what conditions discrepancies occur, particularly focusing on upwelling zones in the deep tropics.