8 resultados para paleoclimate

em Aquatic Commons


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Deterministic chaos in dynamical systems offers a new paradigm for understanding irregular fluctuations. The theory of chaotic dynamical systems includes methods that can test whether any given set of time series data, such as paleoclimate proxy data, are consistent with a deterministic interpretation. Paleoclimate data with annual resolution and absolute dating provide multiple channels of concurrent time series; these multiple time series can be treated as potential phase space coordinates to test whether interannual climate variability is deterministic. Dynamical structure tests which take advantage of such multichannel data are proposed and illustrated by application to a simple synthetic model of chaos, and to two paleoclimate proxy data series.

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In a cooperative agreement between Amoco Production Company and the University of Arizona Geosciences Department, extensive data and resources associated with 15 deep wells drilled in the Great Salt Lake are currently on loan at the University of Arizona. Seismic data, electric and lithologic logs, cuttings and previously-prepared pollen slides will eventually permit a thorough study of both the tectonic and climatic history of the Great Salt Lake region. The preliminary study presented here concentrates on the Late Tertiary and Pleistocene climatic reconstruction of the eastern Great Basin through examination of fossil pollen.

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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).

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EXTRACT (SEE PDF FOR FULL ABSTRACT): Analyses of the modern summer synoptic climatology of Beringia illustrate that the region cannot be treated as a homogenous climatic unit as a result of different circulation controls that operate over the region. GCM (general circulation model) simulations and information from the modern synoptic climatology were used to infer the summer paleosynoptic climatology of the region since the last glacial maximum. ... Variations in these climatic controls offer important implications in assessing the vegetation histories of western Beringia versus eastern Beringia.

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Recent papers provide detailed analyses of more than 40 high-resolution time series culled from the extensive paleoclimate literature that appear to define cyclical elements of the Solar-Insolation/Tidal-Resonance Climate Model. This model was earlier referred to as the Milankovitch/Pettersson Climatic Theory. This paper provides comparable analyses of an additional 20 or so, evidently supportive, climate and volcanic time series. The tree-ring, historical, pollen, cultural, time-frequency, and hydrologic records range in length from 400 to 90,000 years and spatially from Alaska to Tierra del Fuego.

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EXTRACT (SEE PDF FOR FULL ABSTRACT): We describe an empirical-statistical model of climates of the southwestern United States. Boundary conditions include sea surface temperatures, atmospheric transmissivity, and topography. Independent variables are derived from the boundary conditions along 1000-km paths of atmospheric circulation. ... Predictor equations are derived over a larger region than the application area to allow for the increased range of paleoclimate. This larger region is delimited by the autocorrelation properties of climatic data.

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The National Oceanic and Atmospheric Administration Center for Ocean Analysis and Prediction (COAP) in Monterey, California, has assembled information to suggest how NOAA's facilities for observing the ocean and atmosphere might be applied to studies of paleoclimate. This effort resulted, indirectly, in several projects that combine direct observations of the ocean/atmosphere system with studies of past climate of the Pacific region. This article considers concepts that link the two kinds of investigations. It defines the thesis that direct observation of systems that generate paleoclimatic information is the nexus upon which understanding of climatic variability begins and upon which prediction of climate and global change depends.

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Higher resolution time-stratigraphic records suggest correlation of lower frequency paleoclimatic events with Milankovitch obliquity/precessional cycles and of higher frequency events with the evidently resonance-related Pettersson maximum tidal force (MTF) model. Subsequently published records, mainly pollen, seemingly confirm that atmospheric resonances may have modulated past climatic changes in phase with average MTF cycles of 1668, 1112, and 556 years, as calculated in anomalistic years from planetary movements by Stacey. Stacey accepts Pettersson's dating of AD 1433 (517 YBP) for the last major perihelian spring tide based solely on calculations of moon- and earth-orbital relations to the sun. Use of AD 1433 as an origin for the tidal resonance model seemingly continues to provide a best fit for the timing of cyclical patterns in the presented paleoclimate time series.