Glacial sea surface temperatures in the subtropical North Pacific: A comparison of U-k(37)', delta 1(8O), and foraminiferal assemblage temperature estimates

We have investigated glacial-interglacial differences in sea surface temper ature (SST) near Hawaii using two relatively high deposition rate, shallow- water piston cores collected near Oahu, Hawaii. Modem hydrographic data sho w that local surface water temperatures are broadly consistent with the reg ional pattern of SSTs in the southern subtropical North Pacific. Past SSTs were estimated on the basis of three independently measured parameters: (1) U-37(k) values of alkenones, (2) delta O-18 of Globigerinoides ruber, and (3) assemblages of planktonic foraminifera using the modern analog techniqu e (MAT). The two cores yield similar SST records, and if differences in the ecology of foraminifera and coccolithophores are considered, the three dif ferent approaches to estimating SSTs yield consistent results. U-37(k)-base d temperatures, which may represent winter values at this location, were si milar to2.5 degreesC colder during the Last Glacial Maximum than today, whi ch is consistent with the February MAT estimates. The delta O-18-based temp erature estimates, likely biased toward summer temperatures, indicate that the glacial SSTs were at least 1 degreesC cooler than today, which is compa rable to the results of MAT August estimates.