Stable isotope composition of waters in southeastern California 1. Modern precipitation

Abstract

Over a 7‐year period from April 1982 to April 1989, integrated samples of rain and snow were collected at 32 sites by oil‐sealed storage gage stations in (and adjoining) the southeast California desert; station elevations ranged from −65 m to 2280 m, and the collection network covered an area measuring about 400 km in each dimension. Deuterium (δD) analysis of 406 samples shows that the average δD of summer precipitation was −56 per mil (‰) whereas winter values averaged −78‰, averaged annual values were close to −69‰ because most of the area is in a winter‐dominated precipitation regime. We found no correlation between wetness or dryness of a season and the δD of its precipitation. The δ18O versus δD plots show that rain samples define a line of slope 6.5, less than the 8 of the Meteoric Water Line, whereas snow samples define a line of slope 9.2. These differences in slope are the result of isotopic fractionation which occurred during evaporation of raindrops but not during sublimation of snow. Trajectory plots of 68 of the major storm events show that all of the winter storms originated in the Pacific, and passed over high mountains before reaching our collection stations. However, 21 of the 30 summer storms had trajectories that originated either over the Gulf of Mexico or the subtropical Pacific and traveled either west or north to reach our stations, without traversing high mountains. The difference in δD between winter and summer precipitation is due to different air flow patterns during those seasons.

Variable North Pacific influence on drought in southwestern North America since AD 854

“…Results show that 14 C begins to rise at approximately ad 1955, synchronous with or slightly lagging the atmosphere. This is consistent with the rapid transmission of bomb 14 C observed at other sites 23 Previous research indicates that the isotopic composition of precipitation in southern California is largely determined by the storm track delivering precipitation to this region 20 . To further investigate this, we conducted trajectory and clustering analysis and measured the isotopic composition of precipitation from storms reaching the study area between ad 2001 and 2005.…”

“…These factors, variations in the spatial patterns of drought, and the potential nonlinear response of tree growth to moisture availability may explain why there is only weak coherence among independent PDO reconstructions before the twentieth century 19 . Here, we use a new speleothem-based approach to reconstruct North Pacific SSTs by taking advantage of the strong relationship between oxygen isotopes in precipitation in SWNA and North Pacific storm trajectories 20,21 .…”

Late Holocene lake level dynamics inferred from magnetic susceptibility and stable oxygen isotope data: Lake Elsinore, southern California (USA)

“…html]). The amount of winter precipitation is a function of the average position of the winter season polar front, which is forced by changes in the position of the eastern Pacific subtropical high, the polar front jet stream, and its modulation of storm tracks (Weaver 1962;Pyke 1972;Minnich 1984;Lau 1988;Schonher and Nicholson 1989;Enzel et al 1989Enzel et al , 1992Redmond and Koch 1991;Friedman et al 1992;Ely 1997). In turn, large-scale atmospheric patterns that determine the average position of the polar front are modulated by Pacific Ocean sea-surface conditions (Namias 1951;Namias and Cayan 1981;Douglas et al 1982;Lau 1988;Namias et al 1988;Latif and Barnett 1994;Trenberth and Hurrell 1994;Cayan et al 1998;Dettinger et al 1998).…”

“…Climatologically, coastal southwest North America is dominated by winter season (October to March) precipitation, which accounts for up to 80% of the annual water budget (Lynch 1931;USGS 1998;Redmond and Koch 1991;Friedman et al 1992). At Lake Elsinore, the percent of winter precipitation for the months of December through February accounts for 60% of the annual total precipitation (NCDC Weather Station Locator Data [lwf.ncdc.noaa.gov/oa/climate/stationlocator.…”

Environmental isotope investigation of groundwater flow in the Honey Lake Basin, California and Nevada

“…Relative to the GMWL, the Honey Lake Basin LMWL has a slightly lower slope and a signii3cantly lower d-value. These features are common in low-humidity, arid environments (e.g., Ehhalt et al, 1963;Benson and Klieforth, 1989;Friedman et al, 1992;Benson, 1994) and a.xc attributable to the evaporation of raindrops falling through unsaturated air (Friedman et al, 1962;Stewart, 1975;Gat, 1980). The evaporation process enriches a raindrop in the heavy isotopes, shifting its i51g0and 5D…”