Glacial sea surface temperatures in the subtropical North Pacific: A comparison of UK37, δ18O, and foraminiferal assemblage temperature estimates

Abstract

We have investigated glacial-interglacial differences in sea surface temperature (SST) near Hawaii using two relatively high deposition rate, shallow-water piston cores collected near Oahu, Hawaii. Modern hydrographic data show that local surface water temperatures are broadly consistent with the regional pattern of SSTs in the southern subtropical North Pacific. Past SSTs were estimated on the basis of three independently measured parameters: (1) Uk37 values of alkenones, (2) δ18O of Globigerinoides ruber, and (3) assemblages of planktonic foraminifera using the modern analog technique (MAT). The two cores yield similar SST records, and if differences in the ecology of foraminifera and coccolithophores are considered, the three different approaches to estimating SSTs yield consistent results. Uk37-based temperatures, which may represent winter values at this location, were ∼2.5°C colder during the Last Glacial Maximum than today, which is consistent with the February MAT estimates. The δ18O-based temperature estimates, likely biased toward summer temperatures, indicate that the glacial SSTs were at least 1°C cooler than today, which is comparable to the results of MAT August estimates.