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Master Chronology (master + chronology)

Distribution by Scientific Domains
Earth and Environmental Science75%

Selected Abstracts

ENSO history recorded in Agathis australis (kauri) tree rings.

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 1 2008
Part B: 423 years of ENSO robustness
Abstract Part A of this study identified the potential of kauri tree rings for reconstructing the history of past ENSO activity. Plausible indices of multidecadal to centennial-scale ENSO activity (phase dominance and robustness) that could be derived from kauri regional master chronologies are hypothesized here, and they are tested against the instrumental SOI record, using partitioning and graphical analyses. The subset of the indices passing this first screening are then tested for sensitivity to the complex evolving sample depth and site-composition mix that characterizes regional tree-ring chronologies. Corrections for evolving sample depth are developed where possible. The two indices of ENSO activity remaining after these two screening phases (evolving chronology time-series variance and decadal-scale spectral signature) are used to infer 423 years of ENSO robustness and the results are compared to two multiproxy ENSO reconstructions. Results suggest that ENSO robustness (1) peaked in the 20th century, (2) is characterized by persistent 55,80 year cyclicity, (3) was low in the mid-20th century only relative to robust ENSO activity at the beginning and end of that century, (4) reached a pre-20th century peak in the mid-18th century, and (5) was weakest near the beginning of the 19th century. Copyright © 2007 Royal Meteorological Society [source]

Establishing climate,growth relationships for yelloweye rockfish (Sebastes ruberrimus) in the northeast Pacific using a dendrochronological approach

FISHERIES OCEANOGRAPHY, Issue 5 2008
BRYAN A. BLACK
Abstract We applied dendrochronology (tree-ring) methods to develop multidecadal growth chronologies from the increment widths of yelloweye rockfish (Sebastes ruberrimus) otoliths. Chronologies were developed for the central California coast, a site just north of Vancouver Island, British Columbia, and at Bowie Seamount west of the Queen Charlotte Islands, British Columbia. At each site, synchronous growth patterns were matched among otoliths via the process of cross-dating, ensuring that the correct calendar year was assigned to all increments. Each time series of growth-increment measurements was divided by the values predicted by a best-fit negative exponential function, thereby removing age-related trends. These detrended time series were averaged into a master chronology for each site, and chronologies were correlated with monthly averages of sea surface temperatures, upwelling, the Northern Oscillation Index, and the Pacific Decadal Oscillation. The two northern growth chronologies positively correlated with indices of warm ocean conditions, especially from the prior summer through the spring of the current year. During the same period, the California chronology positively correlated with indices of cool ocean conditions, indicating an opposing productivity regime for yelloweye rockfish between the California Current and the Gulf of Alaska. Overall, this study demonstrates how tree-ring techniques can be applied to quickly develop annually resolved chronologies and establish climate,growth relationships across various temporal and spatial scales. [source]

Climate,growth relationships of tropical tree species in West Africa and their potential for climate reconstruction

GLOBAL CHANGE BIOLOGY, Issue 7 2006
JOCHEN SCHÖNGART
Abstract Most tropical regions are facing historical difficulties of generating biologically reconstructed long-term climate records. Dendrochronology (tree-ring studies) is a powerful tool to develop high-resolution and exactly dated proxies for climate reconstruction. Owing to the seasonal variation in rainfall we expected the formation of annual tree rings in the wood of tropical West African tree species. In the central-western part of Benin (upper Ouémé catchment, UOC) and in northeastern Ivory Coast (Comoé National Park, CNP) we investigated the relationship between climate (precipitation, sea surface temperature (SST)) and tree rings and show their potential for climate reconstruction. Wood samples of almost 200 trees belonging to six species in the UOC and CNP served to develop climate-sensitive ring-width chronologies using standard dendrochronological techniques. The relationship between local precipitation, monthly SST anomalies in the Gulf of Guinea, El Niño- Southern Oscillation (ENSO) and ring-width indices was performed by simple regression analyses, two sample tests and cross-spectral analysis. A low-pass filter was used to highlight the decadal variability in rainfall of the UOC site. All tree species showed significant relationships with annual precipitation proving the existence of annual tree rings. ENSO signals could not be detected in the ring-width patterns. For legume tree species at the UOC site significant relationships could be found between SST anomalies in the Gulf of Guinea indicating correlations at periods of 5.1,4.1 and 2.3 years. Our findings accurately show the relationship between tree growth, local precipitation and SST anomalies in the Gulf of Guinea possibly associated with worldwide SST patterns. A master chronology enabled the reconstruction of the annual precipitation in the UOC to the year 1840. Time series analysis suggest increasing arid conditions during the last 160 years which may have large impacts on the hydrological cycles and consequently on the ecosystem dynamics and the development of socio-economic cultures and sectors in the Guinea-Congolian/Sudanian region. [source]

ENSO history recorded in Agathis australis (kauri) tree rings.

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 1 2008
Part A: kauri's potential as an ENSO proxy
Abstract Although many of the main characteristics of the El Niño-Southern Oscillation (ENSO) phenomenon have been established, uncertainties remain concerning its multidecadal- to millennial-scale evolution. Because of the shortness of the instrumental record, we need to resort to proxy-based reconstructions to investigate ENSO's history prior to the mid 19th century, but the available proxy data is limited in both time and space. Here we investigate the potential for ENSO reconstruction from the tree rings of Agathis australis (kauri). Kauri is a long-lived endemic New Zealand conifer and grows in an ENSO teleconnection region not previously represented in ENSO multi-proxy studies. A high quality 423 year kauri regional master chronology (AD 1580,2002) is constructed. Statistical analysis of the period AD 1876,2002 confirms previous findings that kauri tree rings carry a strong regional-scale climate signal and that ENSO is a significant contributor (predominantly via the western pole of the Southern Oscillation). Kauri carries a signal of both ENSO phases, but with a slight El Niño bias. Growth sensitivity is primarily registered through a five-season window, extending from March (prior to growth initiation in September) through to the following May, with strongest relationships across the middle three seasons (June,February). Relationships appear to be stationary. We conclude that kauri has sufficient ENSO event capture skill to make it a useful addition to future multi-proxy ENSO reconstruction efforts. It may also have potential for stand-alone reconstruction of multidecadal- to millennial-scale evolution of ENSO activity, especially ENSO robustness. Copyright © 2007 Royal Meteorological Society [source]