Improving past sea surface temperature reconstructions from the Southern Hemisphere oceans using planktonic foraminiferal census data

We present an improved database of planktonic foraminiferal census counts from the Southern Hemisphere oceans (SHO) from 15 degrees S to 64 degrees S. The SHO database combines three existing databases. Using this SHO database, we investigated dissolution biases that might affect faunal census counts. We suggest a depth/ CO32- threshold of similar to 3800m/ CO32-=similar to-10 to -5 mu mol/kg for the Pacific and Indian Oceans and similar to 4000m/ CO32-=similar to 0 to 10 mu mol/kg for the Atlantic Ocean, under which core-top assemblages can be affected by dissolution and are less reliable for paleo-sea surface temperature (SST) reconstructions. We removed all core tops beyond these thresholds from the SHO database. This database has 598 core tops and is able to reconstruct past SST variations from 2 degrees to 25.5 degrees C, with a root mean square error of 1.00 degrees C, for annual temperatures. To inspect how dissolution affects SST reconstruction quality, we tested the data base with two leave-one-out tests, with and without the deep core tops. We used this database to reconstruct summer SST (SSST) over the last 20ka, using the Modern Analog Technique method, on the Southeast Pacific core MD07-3100. This was compared to the SSST reconstructed using the three databases used to compile the SHO database, thus showing that the reconstruction using the SHO database is more reliable, as its dissimilarity values are the lowest. The most important aspect here is the importance of a bias-free, geographic-rich database. We leave this data set open-ended to future additions; the new core tops must be carefully selected, with their chronological frameworks, and evidence of dissolution assessed.