Title | Deglacial sea surface temperatures of the western tropical Pacific: A new look at old coral |
Publication Type | Journal Article |
Year of Publication | 2004 |
Authors | Cohen A.L, Hart S.R |
Journal | Paleoceanography |
Volume | 19 |
Issue | 4 |
Date Published | Dec 30 |
ISBN Number | 0883-8305 |
Keywords | bolling-allerod, climate-change, coral sr/ca, diagenesis, ion microprobe, last deglaciation, paleotemperature proxy, radiocarbon, record, sea surface temperature, sr/ca, strontium, symbiotic coral, trace-elements, tropical pacific |
Abstract | Using Secondary Ion Mass Spectrometry ( SIMS) ion microprobe techniques, we generated annual Sr/Ca cycles with subweekly resolution from chunks of Porites coral retrieved from a Tahiti barrier reef drill core (149degreesW, 17degreesS), representing the period 13,650 to 13,100 years B.P. The centers of pristine skeletal septa were selectively targeted with a 10 mum diameter ion beam spot, avoiding adjacent pore spaces occupied by secondary aragonite needles. Applying a Sr/Ca-sea surface temperature (SST) calibration equation derived from modern Tahiti Porites having the same low growth rate as the fossil specimens, we obtained SSTs similar to0.5degrees-1.5degreesC cooler during the Bolling-Allerod relative to the present day, with no significant change in seasonality. On the contrary, we estimate that analysis of bulk samples would yield excessively cool Sr/Ca-based SST estimates due to the occupation by secondary aragonite crystals of up to 50% of the skeletal pore space in the ancient samples. We find that growth rate effects on coral Sr/Ca further depress the apparent mean annual derived SSTs (by >3degreesC) and amplify the apparent seasonality by selectively enhancing wintertime cooling. Our microscale analysis of pristine skeleton and application of an appropriate growth-dependent calibration yield Sr/Ca-derived SSTs that are in good agreement with those derived from Mg/Ca ratios of calcitic foraminifera which indicate a continuous postglacial warming of the western tropical Pacific, in phase with the warming of the tropical Atlantic. |
DOI | 10.1029/2004PA001084 |