d18O (SP13LAMX01A): interpretation4_scope: '' has been replaced by 'isotope'

Thermofinnigan Delta V Plus Isotope Ratio Mass Spectrometer coupled with a Kiel IV carbonate device

NBS19, NBS18 and OX (an in-house laboratory standard)

The standard deviation of repeated NBS19 measurements is ~0.06 parts per mille for d18O.

Temp and humidity measured from 2007 till 2013 show constant temp of 8 +/- 0.5 C and humidity close to 100%. Average d18O of 8 drip water samples collected between June, 2007 till July, 2008 is -9.74 +/- 0.48 parts per mille. Glass plate calcite collected over the same period shoed a d18O value of -8.15 parts per mille. So calculated equilibrium temp is 7.6 C which is close to measure cave temp of 7.87 C. Fractionation equation used has not been specified. Supplementary Information.

1. Baker, Andy, and Chris Bradley. "Modern stalagmite ? 18 O: Instrumental calibration and forward modelling." Global and Planetary Change 71.3 (2010): 201-206. 2. Oster, Jessica L., Isabel P. Monta�ez, and Neil P. Kelley. "Response of a modern cave system to large seasonal precipitation variability." Geochimica et Cosmochimica Acta 91 (2012): 92-108. 3. Tooth, Anna F., and Ian J. Fairchild. "Soil and karst aquifer hydrological controls on the geochemical evolution of speleothem-forming drip waters, Crag Cave, southwest Ireland." Journal of Hydrology 273.1 (2003): 51-68. Supplementary information.

Isotopic composition of precipitation in Southern California is largely determined by the storm track delivering precipitation to the region (Friedman, Irving, et al. "Stable isotope composition of waters in southeastern California 1. Modern precipitation." Journal of Geophysical Research: Atmospheres 97.D5 (1992): 5795-5812.). Analysis shows three primary clusters of storms entering the region with the lowest d18O precipitation arriving from North Pacific and highest from tropical Pacific. The trajectory of storms arriving in Southwest North America is strongly dependant on Pacific SST patterns (Ren, Xuejuan, Yaocun Zhang, and Yang Xiang. "Connections between wintertime jet stream variability, oceanic surface heating, and transient eddy activity in the North Pacific." Journal of Geophysical Research: Atmospheres 113.D21 (2008).), which influence the position of high and low pressure centres in the North Pacific and over the North American continent.