Sea Surface Temperatures in Varved Sediments of the Guaymas Basin, Gulf of California

The North American Monsoon (NAM) is responsible for providing about 50% of the southwestern United States' annual precipitation. The paleoclimate history of the NAM is not well understood due to the fact that terrestrial proxies in the US southwest and northern Mexico tend to record winter precipitation rather than summer monsoonal rain. One factor that has been hypothesized to be important for monsoon development is sea-surface temperatures (SSTs) in the Gulf of California (GoC). In order to better understand how SSTs in the GoC have influenced the NAM on recent timescales, we have extracted alkenones, a paleothermometry proxy, from varved sediments in the Guaymas Basin going back at least 2,000 years. The resulting UK37-based SST record is the highest-resolution record of GoC SSTs to date. Comparison to Dwax measurements made on the same sediment core reveals centennial-scale relationships between local SSTs and monsoonal activity in north-central Mexico.