Reconstruction of aridity for the Sierra de la Laguna, Baja California Sur, Mexico

A well-documented history of past climatic conditions is needed to understand and resolve some ecological problems, but the existing climatological records are too short to detect long-term climatic variability and changes. Some trees, such as pines, produce annual tree rings with different widths depending on prevailing environmental conditions, such as climate. Tree-ring analysis of long-lived trees can be used to estimate past variations in climate. The principal aim of this study is to reconstruct aridity for the southern portion of the Baja California Peninsula, by means of dendroclimatologic techniques.

High productivity and upwelling in the California Current during Oxygen-Isotope Stage 3: diatom evidence

Evidence for vigorous coastal upwelling and enhanced diatom productivity during the latter part of Oxygen-Isotope Stage 3 (OIS-3) is suggested by changes in diatom assemblages in laminated sediment from the northern California margin and in bioturbated and laminated sediment from Santa Barbara Basin. These conditions require strong along-shore or off-shore wind stress off California preceding the onset of global glacial conditions.

Some effects of Earth's surface on winter jet stream positions in the Northern Hemisphere and rainfall patterns in northern and central California

EXTRACT (SEE PDF FOR FULL ABSTRACT): This report shows that the mean wintertime polar-front jet stream structure consists of three long waves. Prominent ridges in the jet stream flow occur near the longitudes of India, eastern Pacific/west coast of North America, and eastern Atlantic/British Isles; prominent troughs occur near the longitudes of the Middle East, western Pacific, and western Atlantic/east coast of North America. ... One of the climatological ridges occurs along the west coast of North America ... just off the central Oregon coast. The position of the jet stream at this location appears to be the main reason most Pacific storms pass to the north of California. Sustained rainfall in northern and central California occurs only when the storm track is displaced southward of this climatological position.

Has the California drought returned?

In 1993, enough rain and snow fell to end the 1987-1992 drought in California, at least in most areas. The 1994 season has again been dry and has given rise to questions about whether the drought has returned. But carryover reservoir storage from 1993 has been good and will be meeting a portion of the state's water needs this year. Concern about 1995 has placed California in a "drought watch" mode for 1994, a stage indicating caution but not yet a full drought.

Interdecadal variability in the spatial structure of wind and SST in the California Current system

The physical environment of eastern boundary current systems is rarely uniform in time. ENSO and other perturbations produce profound anomalies in the atmosphere and ocean on interannual to decadal and century time scales. ... The objective of this paper is to describe the temporal variability in the spatial texture of the California Current system, a major eastern boundary current system off the west coast of North America, to provide a base from which to evaluate the effect of climate change - in the recent past, at present, and for the future.

Climate-related long-term faunal changes in a California rocky intertidal community [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The effects of gradual climate change (ie, multi-decadal) on biological communities are not well understood for most natural systems, owing principally to the lack of quantitative observations in early studies. ... We resurveyed invertebrate species on an intertidal transect in central California, first established and surveyed in 1931, to assess shifts in community structure.

California water conditions in 1995

From 1987 through 1992, California endured 6 consecutive years of drought for the second time this century. The drought was broken in most parts of the state by a wet year in 1993, in which runoff was 125 percent of average. But 1994 was again critically dry, with runoff only 40 percent of average statewide, raising fears that the drought had resumed. The "drought watch" of 1994 was finally washed out to sea by two large floods (January and March), which made 1995 one of the wettest years this century and refilled all but a couple of California's major reservoirs. This paper provides information on water conditions and flooding in 1995 and some comparisons with previous years.

Evidence for changes in large-scale upwelling in the California Current over the past 700 years [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Bidecadal radiocarbon measurements on tree rings provide a detailed series of carbon-14 activities at isotopic equilibrium with atmospheric carbon dioxide. ... Most marine environments do not permit development of a comparable series of carbon-14 ages with which to compare the terrestrial tree ring series. However, we have recently begun work on such a series using material from the varved sediments of the Santa Barbara Basin off southern California. ... We now have a nearly continuous record of carbon-14 dates representing the age of the water over the upper 100 meters. ... The ocean reservoir ages show an increase prior to 1450 and a progressive decrease with time after 1450. Although there may be other explanations, we believe this trend is principally the result of changes in large-scale upwelling of water from below 500 meters. These changes were probably also associated with changes in the intensity of the California Current.

On the strength of the California Current: a record from the southern Baja California margin [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): To characterize the strength of the flow of the California Current, we searched in the southern Baja California continental margin, the southernmost site affected by its relatively cool and less saline waters.

Oxygen isotope analysis of corals from the Gulf of California and the Gulf of Panama: application and implications for coral-based paleoclimate reconstructions [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Coral-based reconstruction of past variability of sea surface conditions is improving our understanding of the tropical ocean-atmosphere system. We present oxygen isotope records from corals collected near the tip of Baja California (Baja) and the Gulf of Panama (Saboga).

Integrating varve and tree-ring time series for southern California climate reconstruction: a 20th century outlook [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Our objective is to combine terrestrial and oceanic records for reconstructing West Coast climate. Tree rings and marine laminated sediments provide high-resolution, accurately dated proxy data on the variability of climate and on the productivity of the ocean and have been used to reconstruct precipitation, temperature, sea level pressure, primary productivity, and other large-scale parameters. We present here the latest Santa Barbara basin varve chronology for the twentieth century as well as a newly developed tree-ring chronology for Torrey pine.

Atmospheric circulation patterns associated with tree growth anomalies in the central and southern Sierra Nevada mountains [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): In this work, I examine patterns of atmospheric circulation associated with tree growth anomalies at mid-to-high latitudes (2000-3500 meters).

High-resolution record of climate change in the Owens Lake Basin, California, for the period 52,500 to 12,500 YBP

EXTRACT (SEE PDF FOR FULL ABSTRACT): High-resolution oxygen-18 and total inorganic carbon (TIC) studies of cored sediments from the Owens Lake Basin, California, indicate that Owens Lake was hydrologically open (overflowing) most of the time between 52,500 and 12,500 carbon-14 YBP. ... The lack of a strong correspondence between North Atlantic climate records and the Owens Lake delta-oxygen-18 record has two possible explanations: (1) the sequence of large and abrupt climate change indicated in North Atlantic records is not global in scope and is largely confined to the North Atlantic and surrounding areas, or (2) Owens Lake is located in a part of the Great Basin that is relatively insensitive to the effects of climate perturbations recorded in the North Atlantic region.

A detailed 2,000-year late-Holocene pollen record from Lower Pahranagat Lake, southern Nevada, USA [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Preliminary analysis of 128 pollen samples and 7 radiocarbon dates from a 5-meter-long, 10-centimeter-diameter sediment core retrieved from Lower Pahranagat Lake (elevation 975 meters), Lincoln County, Nevada, gives us a rare, continuous record of vegetation change at 14-year intervals over the past 2,000 years.

A late-Holocene pollen record from Lower Pahrangat Lake, southern Nevada, USA: high resolution paleoclimatic records and analysis of environmental responses to climate change

EXTRACT (SEE PDF FOR FULL ABSTRACT): High resolution paleobotanical records provide sufficient detail to correlate events regionally. Once correlated events can be examined in tandem to determine the underlying inputs that fashioned them. Several localities in the Great Basin have paleobotanical records of sufficient detail to generate regional reconstructions of vegetation changes for the last 2 ka and provide conclusions as to the climates that caused them.