Abstract:
To understand the potential climatic changes as Earth's global mean temperature increases, the climate research community looks to paleoclimate studies for a ground-truthing measure with which to test the accuracy of future climate simulations. The Pliocene Research, Interpretation and Synoptic Mapping Project (PRISM) produces data sets used for climate model - data comparisons. One component of new PRISM work documents paleoclimate conditions within a narrow stratigraphic window centered on Marine Isotope Stage (MIS) KM5.3. This "time slice" represents two orders of magnitude increase in resolution and was chosen by the Pliocene Model Intercomparison Project (PlioMIP) for its Phase 2 experiments. Here we report an initial quantitative faunal analysis for a closely-spaced sequence of samples within core 16 of Site 1208, extending from MIS M2 - KM5.3. Site 1208 is located in the Northwest Pacific Ocean, 3346m beneath the modern day Kuroshio Current Extension, approximately 1400km east of Tokyo. The planktonic foraminiferal assemblage is dominated by Globorotalia inflata. Secondary species include Neogloboquadrina dutertrei and Neogloboquadrina pachyderma (dextral). Minor taxa include Globigerina bulloides, Globigerina calida, Globigerina praedigitata, Globigerinita glutinata, Globigerinoides ruber, Globorotalia crassaformis, Globorotalia tumida, and Orbulina universa. The modern analog technique was used to compare our Pliocene faunal data to a global modern coretop database to determine paleoceanographic estimates based on the closest modern analogs. The Mean Annual Temperature (MAT) at Site 1208 today is 19.55 degrees C, with a seasonal variation of 10 degrees C. Pliocene KM5.3 data estimate a slightly warmer MAT, at 19.78 degrees C, but show a decrease in seasonal variation to 5 degrees C. Phase 1 PlioMIP results from the GISS ModelE2-R Pliocene simulation show an identical MAT at this location and corroborate a minor northward displacement of the paleo-Kuroshio Current relative to its modern position.