Global Synchrony Of Late Pliocene Sea Surface Temperature Variations

As we move beyond assessing Pliocene temperature patterns over broad time intervals (e.g. Piacenzian Warm Period), interesting questions arise as to the variability of temperatures on orbital time scales.   Did the absence of large northern hemisphere ice-albedo feedbacks lead to greatly reduced temperature variations in comparison to the Pleistocene? And would temperature variations be heterogenous regionally,  reflecting the influence of  local insolation anomalies, in contrast to the globally coordinated Pleistocene changes in temperature? We report here orbitally resolved late Pliocene (3.6-2.6 Ma) SST measurements in all ocean basins using the alkenone method.  Sites were selected based on high quality stable isotope data and/or paleomagnetic age control.  SST time series demonstrate that, to first order, ocean surface temperature changes fluctuated synchronously between high and low latitudes, and between the hemispheres.  An obliquity-related signal dominates, but  time series analysis indicates a substantial contribution from precession as well.  In the absence of a strong ice-albedo feedback in the late Pliocene, the evidence thus suggests a dominant role for greenhouse gas forcing of orbital-scale changes in temperature.