Climate Variability in the Gulf of California Over the Last 1,300 years

The North American Monsoon influences the ecosystems and hydroclimate of the southwestern United States and northwestern Mexico. This is a geographically complex region, including the narrow Gulf of California adjacent to the Sierra Madre Occidental. Alongside this complexity, unreliable gridded data products, a lack of long instrumental observations, and limited high-resolution paleoclimate records from the core monsoon region prevent a complete understanding of the variability and drivers of this system on time scales from decades to millennia. Here we generate new proxy records of warm-season sea-surface temperature (SST, based on alkenone U37K ' ${\mathrm{U}}_{37}<^>{{K}<^>{\prime }}$) and terrestrial hydroclimate (based on plant wax hydrogen isotopes) from Gulf of California (GoC) sediment cores spanning 744 to 1980 CE. Although the GoC is an important source of monsoon moisture, we find no one-to-one correlation between SST and our hydroclimate reconstruction over the full time period. Spectral analyses revealed a prominent multicentennial oscillation in the SST reconstruction, as well as multidecadal modes in both records. There is a small cooling trend over the full SST reconstruction, but no clearly delineated Medieval Climate Anomaly or Little Ice Age. Colder periods in our SST reconstruction appear to be associated with periods of increased volcanism, but there is no definitive solar signal. Multidecadal climate variability in this region is likely linked to broader patterns of unforced variability in the Pacific Ocean-atmosphere system, but any coupling between monsoon strength and Gulf of California SST over the Common Era appears to be complex.