These changes in moisture source have been further linked to SST anomalies (SSTa) in the Kuroshio Extension region of the N Pacific, which exerts steering on atmo- spheric circulation and hence moisture sources to the west coast of N America. ... These positive excursions may be linked to warm Kuroshio Extension SSTa, driv- ing greater amplitude waves in the circulation over the N Pacific entraining subtropical moisture sources but generally associated with drier conditions in coastal southern California. Conversely negative isotopic excursions centered on 300 and 800 yr BP may correspond to more N Pacific moisture flux and wetter conditions in coastal southern California, the former of these perhaps associ- ated with the Little Ice Age. In combination with other proxies recording wet/dry climate regime shifts, the information on mois- ture source from precipitation isotopes may thus be particularly helpful in understanding the dynamical causes of hydroclimate shifts. Warm SST anomaly --> less moisture flux -->more enriched precipitation. "Elevated dD values indi- cate more (sub)tropical moisture sources and/or drier conditions, whereas lower dD values are consistent with N Pacific moisture sources and/or more antecedent precipitation. "

Moisture flux from the subtropical North Pacific (driven by SST anomalies in the Kuroshio Extension region)

SEASONALITY: "First, during water uptake, plants are expected to sample the spring growing season precipitation, at the end of the wet season [October-March], as the temperature warms up and before the dry summer months (Feakins and Sessions, 2010; Kahmen et al., 2011; Tipple et al., 2013). During this time, the plants may record the isotopic signature of just a few storms each year heightening variability; however, sedimentary samples integrating a decade might average the signal from > 20 storms. " PARAMETER: "Paleoclimatic interpretation of the precipitation isotopic history recorded in the Crystal Cave has been suggested to record changes in moisture source primarily and local amount effect secondarily (McCabe-Glynn et al., 2013). ... Our record provides an extension of the Crystal Cave isotopic record, from a more southerly coastal location, but likely also records interdecadal variability in the same processes. ... We suggest that the plant leaf wax record preferentially captures spring precipitation isotopic anomalies integrated over decades, providing a sensitive record of atmospheric circulation and moisture source changes. "