A new drought area index (DAI) for the United States has been developed based on a high-quality network of drought reconstructions from tree rings. This DAI is remarkably similar to one developed earlier based on much less data and shows strong evidence for a persistent bidecadal drought rhythm in the western United States since 1700. This rhythm has in the past been associated with possible forcing by the 22-yr Hale solar magnetic cycle and the 18.6-yr lunar nodal tidal cycle. The authors make a new assessment of these possible forcings on DAI using different methods of analysis. In so doing, they confirm most of the previous findings. In particular, there is a reasonably strong statistical association between the bidecadal drought area rhythm and years of Hale solar cycle minima and 18.6-yr lunar tidal maxima. The authors also show that the putative solar and lunar effects appear to be interacting to modulate the drought area rhythm, especially since 1800. These results do not eliminate the possibility that the drought area rhythm is, in fact, internally forced by coupled ocean-atmosphere processes. Recent modeling results suggest that unstable ocean-atmosphere interactions in the North Pacific could be responsible for the drought rhythm as well. However, the results presented here do not easily allow for the rejection of the solar and lunar forcing hypotheses either.
A pacific interdecadal climate oscillation with impacts on salmon production. Mantua, N. J.; Hare, S. R.; Zhang, Y.; Wallace, J. M. & Francis, R. C..
Bulletin of the American Meteorological Society:
Evidence gleaned from the instrumental record of climate data identifies a robust, recurring pattern of ocean- atmosphere climate variability centered over the midlatitude North Pacific basin. Over the past century, the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal timescales. Then is evidence of reversals in the prevailing polarity of the oscillation occurring around 1925, 1947, and 1977; the last two reversals correspond to dramatic shifts in salmon production regimes in the North Pacific Ocean. This climate pattern also affects coastal sea and continental surface air temperatures, as well as streamflow in major west coast river systems, from Alaska to California.
Changes in an Assemblage of Temperate Reef Fishes Associated with a Climate Shift. Sally J. Holbrook; Russell J. Schmitt; John S. Stephens, Jr..
Substantial changes have occurred in assemblages of near shore reef fishes in the Southern California Bight during the past two decades. At two sites off Los Angeles, California , species richness of reef fishes fell 15-25%, and composition shifted from dominance by northern to southern species. Additionally, by 1993, 95% of the fish species had declined in abundance by an average of 69%. Concurrent declines of similar magnitude were observed for several trophic levels of the benthic ecosystem farther north at Santa Cruz Island where populations of surfperches (Pisces: embiotocidae), the standing stock of their crustacean prey, and the biomass of understory microalgae all declined by ~80%. Abundance of fishes fell because declining recruitment of age-0 fish was insufficient ot compensate for losses of older age classes. Annual levels of recruitment of age-0 fishes at all reefs examined fell more than one order of magnitude over two decades and was correlated among years with a broad indicator of Bight-wide productivity, the biomass of macrozooplankton in the California Current. Lower productivity if the coastal marine ecosystem, associated with a climate regime shift in 1976-1977, likely caused large, but unforeseen, impacts on population abundances and trophic structure in near shore benthic communities.
Response of eolian geomorphic systems to minor climate change - examples from the Southern Californian deserts. Lancaster, N..
Eolian processes and landforms are sensitive to changes in atmospheric parameters and surface conditions that affect sediment supply and mobility. The response of eolian geomorphic systems to minor climate change can be examined through process-response models based on a combination of relations between short-term changes in climatic variables and eolian activity and the geologic and geomorphic record of Holocene eolian activity. At both time scales, eolian activity in southern Californian deserts is strongly controlled by Variations in precipitation. Wind energy is not a limiting factor in this region. Formation of eolian deposits is a product of climatic changes that increase sediment supply from fluvial and lacustrine sources and may, therefore, be closely tied to periods of channel cutting and geomorphic instability. During intervening periods, eolian deposits migrate away from sediment source areas and are reworked, modified, and degraded. Remobilization of existing dormant dunes is a product of reduced vegetation cover and soil moisture in periods of drier climates. The major control on these processes is decadal to annual changes in rainfall that determine vegetation cover and soil moisture content.
Sensitivity of electricity and natural gas consumption to climate in the U.S.A. - Methodology and results for eight states. Sailor, David J & Munoz, Ricardo J.