A Four Lake Latitudinal Comparison Along Coastal Southern to Central California: A Late-Holocene Perspective on the Western US Precipitation Dipole.

One of the dominant hydroclimatic features of the western United States is the winter season precipitation dipole. The dipole is characterized by a N-S antiphased precipitation regime presently centered on 40° N latitude (Cayan et al., 1998; Dettinger et al., 1998; Wise, 2010). For example, the position of the dipole dictates where CA receives its winter precipitation; thus, it is critical to understand the dipole from a paleoperspective, which at present is poorly known. Here, we present four lake sites spanning 33°-36° N latitude along coastal CA. These sites include: Lake Elsinore, Crystal Lake, Zaca Lake, and Abbott Lake. All four of these sites are located south of the dipole's average historic (since 1950 AD) latitude. The predominant hydroclimatic indicator is similar for each basin (i.e., grain size); although, several other indicators are used for independent verification/assessment of the grain size interpretation. Notably, these lakes contain varied age control, which limits site-to-site correlation without consideration of age model dependence. Following a Bayesian framework, MCMC algorithms in conjuction with radiocarbon dating will be used to estimate timestamps of sediment deposits with a degree of statistical uncertainty. Samples from the posterior distribution will be used to correlate hydroclimatic features between sites. Included in this analysis are tree ring records from the region to assess the similarities and differences as recorded in annually resolved tree ring drought reconstructions and decadally resolved lake sediment hydroclimatic records. Finally, the four sites are assessed in the context of tropical and north Pacific SST forcing.