title: Prolonged California aridity linked to climate warming and Pacific sea surface temperature.
abstract: California has experienced a dry 21(st) century capped by severe drought from 2012 through 2015 prompting questions about hydroclimatic sensitivity to anthropogenic climate change and implications for the future. We address these questions using a Holocene lake sediment record of hydrologic change from the Sierra Nevada Mountains coupled with marine sediment records from the Pacific. These data provide evidence of a persistent relationship between past climate warming, Pacific sea surface temperature (SST) shifts and centennial to millennial episodes of California aridity. The link is most evident during the thermal-maximum of the mid-Holocene (~8 to 3 ka; ka = 1,000 calendar years before present) and during the Medieval Climate Anomaly (MCA) (~1 ka to 0.7 ka). In both cases, climate warming corresponded with cooling of the eastern tropical Pacific despite differences in the factors producing increased radiative forcing. The magnitude of prolonged eastern Pacific cooling was modest, similar to observed La Niña excursions of 1(o) to 2 °C. Given differences with current radiative forcing it remains uncertain if the Pacific will react in a similar manner in the 21st century, but should it follow apparent past behavior more intense and prolonged aridity in California would result.
authors.affiliation: Department of Geography, University of California, Los Angeles, 1255 Bunche Hall, Los Angeles, CA 90095-1524, USA.
authors.forename: Glen M
authors.initials: GM
authors.lastname: MacDonald
authors.affiliation: Department of Geography and Centre for Environment and Sustainability, University of Western Ontario, 1151 Richmond St., North, London, Ontario, N6A 5C2, Canada.
authors.forename: Katrina A
authors.initials: KA
authors.lastname: Moser
authors.affiliation: Department of Geography-Geology, Illinois State University, Campus Box 4400, Normal, IL 61790-4400, USA.
authors.forename: Amy M
authors.initials: AM
authors.lastname: Bloom
authors.affiliation: School of Geography and Archaeology, National University of Ireland, Galway, Galway, Ireland.
authors.forename: Aaron P
authors.initials: AP
authors.lastname: Potito
authors.affiliation: Department of Geography, University of Georgia, 210 Field Street, Athens, GA 30602-001, USA.
authors.forename: David F
authors.initials: DF
authors.lastname: Porinchu
authors.affiliation: Smithsonian Environmental Research Center, Edgewater, MD, 21037-0028, USA.
authors.forename: James R
authors.initials: JR
authors.lastname: Holmquist
authors.affiliation: Westminster School, Geography, London, SW1P 3PF, UK.
authors.forename: Julia
authors.initials: J
authors.lastname: Hughes
authors.affiliation: Department of Geography, University of California, Los Angeles, 1255 Bunche Hall, Los Angeles, CA 90095-1524, USA.
authors.forename: Konstantine V
authors.initials: KV
authors.lastname: Kremenetski