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Weinheimer, AL, Cayan DR.  1997.  Radiolarian assemblages from Santa Barbara Basin sediments: Recent interdecadal variability. Paleoceanography. 12:658-670.   10.1029/97pa00986   AbstractWebsite

Santa Barbara Basin contains a sedimentary record ideal for high-resolution paleoclimate studies because of the annual varves and regional-to global-scale climate signals preserved in the sediments [Lange er al., 1990; Kennett and Ingram, 1995], even though it does not lie directly in the path of the California Current. A nearly 100-year annual time series (1909-1991) of polycystine radiolarian assemblages from Santa Barbara Basin (SBB) sediments was analyzed to the species level. Counts on a replicate SBB core, dated 1870-1987, indicate that results are reproducible and the flux of a few representative species can be extrapolated to estimate fluxes of environmentally sensitive groups. The frequency of species occurrences resembles a lognormal curve and year-by-year comparisons of species fluxes revealed only modest changes in the assemblages from 1909-1991, indicating that the assemblages represent a single oceanic province. For paleoceanographic analysis of the radiolarian record, species were combined into groups according to the water mass in which they occur. To test this method, temperature-sensitive species were identified using t-tests. This generated warm and cool classes exhibiting trends in relative flux similar to those of the water mass groups. Both total nux and relative fluxes of water mass groups relate to low-frequency, decadal-scale temperature fluctuations, but not strongly to El Nino-Southern Oscillation events. Generally, fluxes of species from different water masses covary suggesting changing carrying capacities and productivity through time, while the consistent inverse relationship in relative fluxes indicate variability in climate. The subtle, decadal-scale changes in assemblages, diversity, and increase in percent warm water-fauna are consistent with a spin-down of the California Current System suggested by other records.

Weinheimer, AL, Kennett JP, Cayan DR.  1999.  Recent increase in surface-water stability during warming off California as recorded in marine sediments. Geology. 27:1019-1022.   10.1130/0091-7613(1999)027<1019:riisws>2.3.co;2   AbstractWebsite

Warming of surface waters in the California Current since the 1950s has coincided with a significant decline in zooplankton volume. This has been attributed to reduced upwelling of nutrient-rich waters caused by increased thermal stratification across the thermocline. Proxy microfossil evidence preserved in the Santa Barbara Basin suggests that stability increased early in the 1900s, intensified after the early 1940s, and became well established by 1960. Accumulation of up-welled radiolarians in the basin has steadily declined since 1900, while oxygen isotopes in surface-dwelling planktonic foraminifera reflect increasing surface temperatures. Comparison of the delta(18)O records between surface and thermocline-dwelling planktonic foraminifera reveals that the temperature difference between surface and thermocline water has increased during the twentieth century. Instrumental records of surface and thermocline temperatures, monitored since 1950, support these results. This evidence suggests that relaxation of North Pacific anticyclonic gyre circulation deepened isopycnics, causing onshore movement of warmer, less saline waters and reduced upwelling of cool, nutrient-rich waters.

White, WB, Lean J, Cayan DR, Dettinger MD.  1997.  Response of global upper ocean temperature to changing solar irradiance. Journal of Geophysical Research-Oceans. 102:3255-3266.   10.1029/96jc03549   AbstractWebsite

By focusing on time sequences of basin-average and global-average upper ocean temperature (i.e., from 40 degrees S to 60 degrees N) we find temperatures responding to changing solar irradiance in three separate frequency bands with periods of >100 years, 18-25 years, and 9-13 years. Moreover, we find them in two different data sets, that is, surface marine weather observations from 1990 to 1991 and bathythermograph (BT) upper ocean temperature profiles from 1955 to 1994. Band-passing basin-average find each frequency component in phase across the Indian, Pacific, and Atlantic Oceans, yielding global-average records with maximum amplitudes of 0.04 degrees +/- 0.01 degrees K and 0.07 degrees 0.01 degrees K on decadal and interdecadal scales, respectively. These achieve maximum correlation with solar irradiance records (i.e., with maximum amplitude 0.5 W m(-2) at the top of the atmosphere) al phase lags ranging from 30 degrees to 50 degrees. From the BT data set, solar signals in global-average temperature penetrate to 80-160 m, confined to the upper layer above the main pycnocline. Operating a global-average heat budget for the upper ocean yields sea surface temperature responses of 0.01 degrees-0.03 degrees K and 0.02 degrees-0.05 degrees K on decadal and interdecadal scales, respectively, from the 0.1 W m(-2) Penetration of solar irradiance to the sea surface. Since this is of the same order as that observed (i.e., 0.04 degrees-0.07 degrees K), we can infer that anomalous heat from changing solar irradiance is stored in the upper layer of the ocean.

Knowles, N, Cronkite-Ratcliff C, Pierce DW, Cayan DR.  2018.  Responses of unimpaired flows, storage, and managed flows to scenarios of climate change in the San Francisco Bay-Delta Watershed. Water Resources Research. 54:7631-7650.   10.1029/2018wr022852   AbstractWebsite

Projections of meteorology downscaled from global climate model runs were used to drive a model of unimpaired hydrology of the Sacramento/San Joaquin watershed, which in turn drove models of operational responses and managed flows. Twenty daily climate change scenarios for water years 1980-2099 were evaluated with the goal of producing inflow boundary conditions for a watershed sediment model and for a hydrodynamical model of the San Francisco Bay-Delta estuary. The resulting time series of meteorology, snowpack, unimpaired flow, reservoir storage, and managed flow were analyzed for century-scale trends. In the Sacramento basin, which dominates Bay-Delta inflows, all 20 scenarios portrayed warming trends (with a mean of 4.1 degrees C) and most had precipitation increases (with a mean increase of 9%). Sacramento basin snowpack water equivalent declined sharply (by 89%), which was associated with a major shift toward earlier unimpaired runoff timing (33% more flow arriving prior to 1 April). Sacramento basin reservoirs showed large declines in end-of-September storage. Water-year averaged outflows increased for most scenarios for both unimpaired and impaired flows, and frequency of extremely high daily unimpaired and impaired flows increased (increases of 175% and 170%, respectively). Managed Delta inflows were projected to experience large increases in the wet season and declines in the dry season. Changes in management strategy and infrastructure can mitigate some of these changes, though to what degree is uncertain.

Peterson, DH, Cayan DR, DiLeo J, Noble M, Dettinger M.  1994.  The role of climate in estuarine variability. American Scientist. 83:58-67. Abstract
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