Energy balance constraints on 18O based paleo-sea surface temperature estimates


  • Mark A. Horrell


Oxygen isotope based paleo-sea surface temperature estimates from the tropics consistently indicate values well below that of the present (27°C), with some estimates from the Middle Tertiary reaching as low as 15°C. Using an energy balance model allows a test of several scenarios for producing and maintaining such cool tropical temperatures; of particular interest are (1) increased cloud cover, (2) increased zonal wind speed, and (3) increased poleward energy transport. The latter is the most likely process since enhanced poleward energy transport would lead to warmer poles, a point which agrees well with high latitude geological and paleontological evidence. However, none of the scenarios tested could provide the degree of equatorial cooling needed to be in agreement with paleotemperature estimates. In summary, published estimates of cool equatorial surface temperatures must be questioned since they cannot be supported by energy balance arguments or geological evidence.