Subtropical Pacific Ocean Temperature Fluctuations in the Common Era: Multidecadal Variability and Its Relationship With Southwestern North American Megadroughts

Variability of North Pacific sea surface temperatures (SSTs) on multidecadal timescales plays an important role in modulating global climate and regional hydroclimate. The principle modern phenomenon associated with this variability is the Pacific Decadal Oscillation (PDO); however, our understanding of the PDO and multidecadal SST variability more broadly is limited to SST observations from the historical era and land-based proxy reconstructions. Here, we reconstruct multidecadal Pacific Ocean SST variability with an 1,800-year, continuous, high-resolution alkenone-derived SST reconstruction from Baja California, a region sensitive to changes in the PDO, and compare the record with a reconstruction of Southwestern North American hydroclimate. Our SST reconstruction displays persistent multicentennial and discontinuous intervals of multidecadal variability with periodicities similar to instrumental PDO observations. The most severe droughts in Southwestern North America during the last two millennia are coeval with strong multidecadal variability, suggesting that multidecadal SST variability plays an important role in regional megadroughts.