Tropical Sea Surface Temperature
Using the oxygen isotope and Sr/Ca thermometers measured in Barbados corals spanning the last deglaciation, we first concluded that tropical sea surface temperatures were as much as 5 degrees cooler during the last glacial period. Although we have since abandoned the Sr/Ca thermometer based on our coral culture experiments; our sea surface temperature estimates still stand based on the strength of the original oxygen isotope data. Several other proxies, including noble gas paleothermometers, tropical ice cores, and some pollen-based reconstructions, confirmed cool tropical temperatures. Prior to our tropical sea surface temperature results, the CLIMAP sea surface temperature reconstructions based on statistical analyses of microfossil abundances in deep sea cores, indicated constant tropical sea surface temperatures. The assumption of constant tropical sea surface temperatures and polar regions that varied synchronously had a profound influence on the course of research for over two decades. The climate and paleoceanographic communities looked to atmospheric CO2 and deep ocean currents to transmit climate signals from the north to the south either over (CO2) or under (NADW) the tropics. Recognition that the tropics are not thermostated at present day temperatures but are free to change by more than 5°C shifted the climate community's focus to the role of the tropics in possibly driving global climate change. This remains one of the most exciting and challenging topics in paleoceanographic research. Our current research is directed toward development and testing new paleotemperature proxies in corals through culture experiments and application of these new proxy thermometers to our coral sample set. In addition, we are preparing a series of papers that reanalyze the global alkenone, Mg/Ca, δ18O, and foraminifera transfer function sea surface temperature estimates based on our thermocline/flux model.
- [PDF] Guilderson T.P., R.G. Fairbanks and J.L. Rubenstone, 2001. Tropical Atlantic coral oxygen isotopes: glacial-interglacial sea surface temperatures and climate change; Mar. Geol., vol. 172, no. 1-2, pp. 75-89.
- [PDF] Moore, M.D., C.D. Charles, J.L. Rubenstone, and R. G. Fairbanks, 2000. U/Th-dated sclerosponges from the Indonesian Seaway record subsurface adjustments to west Pacific winds. Paleoceanography, 15, 4, 404-416.
- [PDF] Guilderson, T., R.G. Fairbanks and J. Rubenstone. 1994. Tropical temperature variations 0-20,000 Years: modulating interhemispheric climate change. Science, 263, 663-665.
- Ravelo, C.A. and R.G. Fairbanks, 1992. Reconstructing the photic zone temperature range using .18O measured on multiple species of planktonic foraminifera. Paleoceanography, 7, no.6, 815-832.
- [PDF] Shemesh, A., C.D. Charles and R.G. Fairbanks, 1992. Oxygen isotopes in biogenic silica: a new method to calculate global changes in ocean temperature and isotopic composition during climate events. Science, 256, 1434-1436.