Sea Surface Temperature Variability on the California Margin During the Common Era

Understanding the timing and amplitude of regional temperature records is key toward understanding causal mechanisms of global temperature change. Temperature changes over the Common Era have been attributed to both internal and external forcing including variability in solar irradiance and volcanism, as well as changes in ocean-atmospheric circulation. High-resolution ocean records of sea surface temperature (SST) from the Pacific are relatively lacking, but can elucidate regional circulation changes and contribute to data coverage for global temperature syntheses.

Santa Barbara Basin (SBB) preserves an annual to decadal record of proxy sea surface temperatures over the past 2000 years in laminated marine sediments. We present a spliced record of SST and thermoclinal temperatures from SPR0901-10BC, SPR0901-02KC and MV0508-32JPC (34° 16.847' N, 120° 02.268' W) based on the foraminiferal proxies Mg/Ca, δ¹⁸O, N. incompta/N. pachyderma coiling ratio and size normalized shell weight. These records indicate that the eastern Pacific region reflects the global trends of a warmer first millennium than second millennium, with a long term cooling trend over the second millennium. However, in SBB SSTs were variable through the Little Ice Age, and the coldest period of the Common Era was at the end of the Little Ice Age in the 19^th century. These results emphasize the regional expression of SSTs during the Common Era, and the likely important role of ocean- atmosphere circulation in determining these differences.