Timing of Late Quaternary sea surface temperature change: Evidence from high-resolution Globigerina bulloides Mg/Ca records from the California Margin

The role of the Pacific Ocean in climate evolution remains a fundamental question in paleoceanography of the late Quaternary. High-resolution sedimentary sections from the California margin provide a valuable opportunity to address the mechanisms of how heat is transmitted through the extra-tropical Pacific by closely examining the phasing of sea surface temperature relative to ice volume changes in a region far removed from the direct effects of continental ice sheets. We present high-resolution Globigerina bulloides Mg/Ca records from two sites on the central California Margin. ODP Site 1017E (off Point Conception, California; 955 m) provides a millennial-scale sea surface temperature record to 60 kyr; MD2504 (Santa Barbara Basin; 440 m) provides a centennial-scale record through the Last Glacial Maximum. These records, together with oxygen isotopic data, provide a window into the timing of sea surface temperature change on the deglacial as well as during short-term climate events in Marine Isotope Stage 3. At Site 1017E temperature oscillations in MIS3 were synchronous with δ ¹⁸O and had an amplitude of as much as 6° C, on average 2° C larger than those inferred by δ ¹⁸O. Comparison between the Mg/Ca records from the two sites indicates that within the resolution of the age models, the amplitude and timing of SST changes were equivalent between Santa Barbara Basin and Point Conception, suggesting that there was not a strong local overprint on temperature change along the California margin. Mg/Ca records indicate that full glacial sea surface temperatures were approximately 8° C. Both sites show a prominent pre-Bolling temperature oscillation of 2-3° C, followed by an abrupt glacial-interglacial temperature change of 7-8° C that occurred synchronously with δ ¹⁸O.