Download or read book Interannual and Decadal Climate Variability in Coral and Instrumental Records with a Focus on the Western Indian Ocean written by David Ericsson Hunter and published by . This book was released on 2003 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Coral Records of Central Tropical Pacific Sea surface Temperature and Salinity Variability Over the 20th Century written by Intan Suci Nurhati and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate forecasts of future regional temperature and rainfall patterns in many regions largely depend on characterizing anthropogenic trends in tropical Pacific climate. However, strong interannual to decadal-scale tropical Pacific climate variability, combined with sparse spatial and temporal coverage of instrumental climate datasets in this region, have obscured potential anthropogenic climate signals in the tropical Pacific. In this dissertation, I present sea-surface temperature (SST) and salinity proxy records that span over the 20th century using living corals from several islands in the central tropical Pacific. I reconstruct the SST proxy records via coral Sr/Ca, that are combined with coral oxygen isotopic (d18O) records to quantify changes in seawater d18O (hereafter d18Osw) as a proxy for salinity. Chapter 2 investigates the spatial and temporal character of SST and d18Osw-based salinity trends in the central tropical Pacific from 1972-1998, as revealed by corals from Palmyra (6°N, 162°W), Fanning (4°N, 159°W) and Christmas (2°N, 157°W) Islands. The late 20th century SST proxy records exhibit warming trends that are larger towards the equator, in line with a weakening of equatorial Pacific upwelling over this period. Freshening trends revealed by the salinity proxy records are larger at those sites most affected by the Inter-Tropical Convergence Zone (ITCZ), suggesting a strengthening and/or an equatorward shift of the ITCZ. Taken together, the late 20th century SST and salinity proxy records document warming and freshening trends that are consistent with a trend towards a weakened tropical Pacific zonal SST gradient under continued anthropogenic forcing. Chapter 3 characterizes the signatures of natural and anthropogenic variability in central tropical Pacific SST and d18Osw-based salinity over the course of 20th century using century-long coral proxy records from Palmyra. On interannual timescales, the SST proxy record from Palmyra tracks El Niño-Southern Oscillation (ENSO) variability. The salinity proxy record tracks eastern Pacific-centered ENSO events but is poorly correlated to central Pacific-centered ENSO events - the result of profound differences in precipitation and ocean advection that occur during the two types of ENSO. On decadal timescales, the coral SST proxy record is significantly correlated to the North Pacific Gyre Oscillation (NPGO), suggesting that strong dynamical links exist between the central tropical Pacific and the North Pacific. The salinity proxy record is significantly correlated to the Pacific Decadal Oscillation (PDO), but poorly correlated to the NPGO, suggesting that, as was the case with ENSO, these two modes of Pacific decadal climate variability have unique impacts on equatorial precipitation and ocean advection. However, the most striking feature of the salinity proxy record is a prominent late 20th century freshening trend that is likely related to anthropogenic climate change. Taken together, the coral data provide key constraints on tropical Pacific climate trends, and when used in combination with model simulations of 21st century climate, can be used to improve projections of regional climate in areas affected by tropical Pacific climate variability.
Download or read book Global Change in the Holocene written by John Birks and published by Routledge. This book was released on 2014-02-24 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Holocene spans the 11,500 years since the end of the last Ice Age and has been a period of major global environmental change. However the rate of change has accelerated during the last hundred years, due largely to human impacts and this has led to a growing concern for the future of our environmental resources. Global Change in the Holocene demonstrates how reconstructing the record of past environmental change can provide us with essential knowledge about how our environment works and presents the reader with an informed viewpoint from which to project realistic future scenarios. The book brings together key techniques that are widely used in Holocene research, such as radiocarbon dating, dendrochronology and sediment analysis and offers a comprehensive analysis of various archives of environmental change including instrumental and documentary records, corals, lake sediments, glaciers and ice cores. This reference will be an informative and cutting-edge resource for all researchers in the fields of climate change, environmental science, geography, palaeoecology and archaeology.
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2004 with total page 806 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pacific Climate Variability written by Sara C. Sanchez and published by . This book was released on 2018 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation aims to understand the mechanisms and consequences of the low frequency "unforced" component of variability in the climate system using interannual and decadal variability as a platform to investigate phenomena thought to be sensitive to greenhouse gas emissions. To combat the lack of temporally extended instrumental observations, this dissertation relies on coral geochemistry and Earth System Models to identify the historical range of Pacific climate variability. Chapter 2 describes the analysis of a roughly 200 year-long coral record from Clarion Island, in the Revillagigedos Archipelago, Mexico. This record expresses substantial decadal variability in the oxygen isotopes, strongly coherent with other paleoproxies in the central equatorial Pacific and in Southern California, indicative of a coordinated system of ocean-atmospheric interaction. To best resolve the key processes involved, "forward models" are employed to interpret the decadal variability in the coral record. The third chapter complements the first by addressing a mechanism responsible for the modulation of decadal variability in the North Pacific; the Pacific Meridional Mode (PMM). The Community Earth System Model-Last Millennium Ensemble (CESM-LME) is used to estimate the historical range of PMM variability, highlighting the considerable power of natural variability within the system. I investigate the physical processes associated with adjustments in PMM variance, emphasizing that relatively small anomalies in the background state have a significant influence on PMM variability. Chapter 4 examines the roles of physical and biologically mediated processes on coral calcification from within an equatorial Pacific coral reef. Motivated by the biogeochemical implications of the previous sections, this work examines the manifestation of pH tracers in coral skeletal tissue across a network of diverse, monitored reef sites at Palmyra Atoll. Corals were analyzed for [delta]11B, trace metal, [delta]18O, and [delta]13C composition. Despite a narrow range in the pH of seawater, high variance in [delta]11B were observed between sites, and within single sites, suggesting that individual coral colonies have differential capacities to regulate pH variability and other environmental stressors.
Download or read book Annual Report written by Scripps Institution of Oceanography and published by . This book was released on 2004 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Historical Climate Variability Reconstructed from Massive Coral Records in the Western Indian Ocean written by Jean Vincent Arnaud Nicolas and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Explorations written by and published by . This book was released on 2003 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Decadal Climate Variability in the Western Tropical Atlantic and the Potential for Proxy Records from the Coral Siderastrea Siderea written by Nathalie E. G. Smith and published by . This book was released on 1997 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Natural Climate Variability on Decade to Century Time Scales written by National Research Council and published by National Academies Press. This book was released on 1996-08-30 with total page 645 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume reflects the current state of scientific knowledge about natural climate variability on decade-to-century time scales. It covers a wide range of relevant subjects, including the characteristics of the atmosphere and ocean environments as well as the methods used to describe and analyze them, such as proxy data and numerical models. They clearly demonstrate the range, persistence, and magnitude of climate variability as represented by many different indicators. Not only do natural climate variations have important socioeconomic effects, but they must be better understood before possible anthropogenic effects (from greenhouse gas emissions, for instance) can be evaluated. A topical essay introduces each of the disciplines represented, providing the nonscientist with a perspective on the field and linking the papers to the larger issues in climate research. In its conclusions section, the book evaluates progress in the different areas and makes recommendations for the direction and conduct of future climate research. This book, while consisting of technical papers, is also accessible to the interested layperson.
Download or read book Decadal Variability of the Atlantic Meridional Overturning Circulation written by Martha Weaver Buckley and published by . This book was released on 2011 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the mean, the Atlantic Ocean transports 1 to 1.5 PW of heat northward, and estimates suggest that 60% of this heat transport is associated with a circulation that reaches the cold waters of the abyss. Due to the role of the Atlantic Meridional Overturning Circulation (AMOC) in ocean heat transport, numerous studies have suggested that AMOC variability plays a role in climate variability on a wide range of timescales. My focus is AMOC and ocean buoyancy variability on decadal timescales. Decadal variability of sea surface temperature (SST) has been observed in the instrumental record and climate proxy data and is thought to be linked to variability in the AMOC. On the other hand, according to the thermal wind relation, buoyancy anomalies on the boundaries lead to anomalies in the AMOC, a fact that has been utilized in order to reconstruct the MOC at 26.5'N using data collected by the RAPID array. Here, I study decadal AMOC and buoyancy variability in a coupled and oceanonly GCMs run in idealized geometries. I focus on understanding the mechanisms of decadal variability of the AMOC, both the role of the AMOC in creating decadal buoyancy anomalies and the response of the AMOC to buoyancy anomalies. I find that decadal AMOC variability is driven by buoyancy anomalies near the western boundary of the subpolar gyre. When a buoyancy anomaly hits the western boundary, it is advected southward by the deep western boundary current. Via the thermal wind relation, buoyancy anomalies on the boundaries result in anomalies in the shear of the zonally integrated meridional velocity. Buoyancy anomalies on the eastern boundary are observed to be negligible, except in the subpolar gyre, indicating that negative (positive) buoyancy anomalies on the western boundary lead to a spin up (down) of the AMOC. The AMOC is observed to respond passively to buoyancy anomalies on the western boundary: although variability of the AMOC does lead to variability in the meridional transport of heat and salt, these transports are not responsible for creating the buoyancy anomalies on the western boundary that drive the AMOC variability. While the structure of the buoyancy anomalies is found to change with model bathymetry, in all the models studied the buoyancy variability is due to an oceanonly mode. In some cases, the mlode is weakly damped (large Q-factor), resulting in regular, predictable oscillations. In other cases, the ocean-only imode is highly damped (small Q-factor) and must be excited by stochastic atmospheric variability, resulting in irregular, less predictable variability. In nature, buoyancy anomalies along the western boundary might be created ill a number ways, including local baroclinic instability, baroclinic Rossby waves impinging on the western boundary, advection of anomalies from tropics, and advection/ propagation of convectively created anomalies from polar regions. In our models the dominant sources of buoyancy anomalies on the western boundary are local baroclinic instability and the propagation of baroclinic Rossby waves originating near the eastern boundary. However, we expect the response of the AMOC to decadal buoyancy anomalies on the western boundary to be similar regardless of the origin of these buoyancy anomalies.
Download or read book Surface Temperature Reconstructions for the Last 2 000 Years written by National Research Council and published by National Academies Press. This book was released on 2007-01-05 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: In response to a request from Congress, Surface Temperature Reconstructions for the Last 2,000 Years assesses the state of scientific efforts to reconstruct surface temperature records for Earth during approximately the last 2,000 years and the implications of these efforts for our understanding of global climate change. Because widespread, reliable temperature records are available only for the last 150 years, scientists estimate temperatures in the more distant past by analyzing "proxy evidence," which includes tree rings, corals, ocean and lake sediments, cave deposits, ice cores, boreholes, and glaciers. Starting in the late 1990s, scientists began using sophisticated methods to combine proxy evidence from many different locations in an effort to estimate surface temperature changes during the last few hundred to few thousand years. This book is an important resource in helping to understand the intricacies of global climate change.
Download or read book Interannuale Klimavariabilit t Im Tropischen Indischen Ozean written by Astrid Baquero-Bernal and published by . This book was released on 2005 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Interannual Climate Variability in the Tropical Indian Ocean written by Astrid Baquero Bernal and published by . This book was released on 2004 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Assessment of Climate Change over the Indian Region written by R. Krishnan and published by Springer Nature. This book was released on 2020-06-12 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book discusses the impact of human-induced global climate change on the regional climate and monsoons of the Indian subcontinent, adjoining Indian Ocean and the Himalayas. It documents the regional climate change projections based on the climate models used in the IPCC Fifth Assessment Report (AR5) and climate change modeling studies using the IITM Earth System Model (ESM) and CORDEX South Asia datasets. The IPCC assessment reports, published every 6–7 years, constitute important reference materials for major policy decisions on climate change, adaptation, and mitigation. While the IPCC assessment reports largely provide a global perspective on climate change, the focus on regional climate change aspects is considerably limited. The effects of climate change over the Indian subcontinent involve complex physical processes on different space and time scales, especially given that the mean climate of this region is generally shaped by the Indian monsoon and the unique high-elevation geographical features such as the Himalayas, the Western Ghats, the Tibetan Plateau and the adjoining Indian Ocean, Arabian Sea, and Bay of Bengal. This book also presents policy relevant information based on robust scientific analysis and assessments of the observed and projected future climate change over the Indian region.
Download or read book Past Climate Variability through Europe and Africa written by Richard W. Battarbee and published by Springer Science & Business Media. This book was released on 2004-12-03 with total page 653 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on two complementary time-scales, the Holocene (approximately the last 11,500 years) and the last glacial-interglacial cycle (approximately the last 130,000 years) to synthesize evidence of climate variability at the regional and continental scale across Europe and Africa. This is the first examination of historical climate variations at such a scale, and thus sets a benchmark for future research.
