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Decadal Climate Variability In The Western Tropical Atlantic And The Potential For Proxy Records From The Coral Siderastrea Siderea
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Book Synopsis Decadal Climate Variability in the Western Tropical Atlantic and the Potential for Proxy Records from the Coral Siderastrea Siderea by : Nathalie E. G. Smith
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:
Book Synopsis Interannual and Decadal Climate Variability in Coral and Instrumental Records, with a Focus on the Western Indian Ocean by : David Ericsson Hunter
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:
Book Synopsis Influence of the Sea Surface Temperature Decadal Variability on Tropical Precipitation: West African and South American Monsoon by : Julián Villamayor
Download or read book Influence of the Sea Surface Temperature Decadal Variability on Tropical Precipitation: West African and South American Monsoon written by Julián Villamayor and published by Springer. This book was released on 2019-07-05 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book the Sea Surface Temperature (SST) patterns of decadal-to-multidecadal variability observed and simulated by 17 general circulation models (GCMs) are analyzed. Furthermore, their impact on precipitation in West Africa and South America and the atmospheric mechanisms involved are assessed. Through this analysis, the effect of external forcings on these impacts and the relative contribution of decadal-to-multidecadal variability patterns of SST to precipitation are presented in depth. Finally, a humid period in the West African region of the Sahel during the 19th century, previously little documented, is analyzed using an atmospheric GCM. The monsoons of West Africa and South America have shown changes in the timescales of a few decades. Previous work suggests a relationship with patterns of decadal-to-multidecadal variability of SST, such as global warming and the Atlantic and Pacific variability. However, the dynamics underlying this relationship and its simulation by current GCMs had not been addressed in a consistent manner. This is the main motivation of this book. The results of this book not only represent a great step forward in our understanding of the changes in the precipitation regimes of the studied regions, but they can also be of great help for the improvement of decadal prediction systems and the associated social consequences.
Book Synopsis Little Ice Age Climate in the Western Tropical Atlantic Inferred from Coral Geochemical Proxies by : Alice Elizabeth Alpert
Download or read book Little Ice Age Climate in the Western Tropical Atlantic Inferred from Coral Geochemical Proxies written by Alice Elizabeth Alpert and published by . This book was released on 2016 with total page 245 pages. Available in PDF, EPUB and Kindle. Book excerpt: Paleoclimate archives place the short instrumental record of climate variability in a longer temporal context and allow better understanding of the rate, nature and extent by which anthropogenic warming will impact natural and human systems. The ocean is a key component of the climate system and records of past ocean variability are thus essential for characterizing natural variability and quantifying climate sensitivity to radiative forcing. Coral skeletons are high-resolution archives of tropical sea surface temperatures (SSTs), but inconsistencies call the accuracy of existing coral proxy records into question. In this thesis, I first quantify the errors associated with the traditional coral thermometer, Sr/Ca, by comparing in situ logged SST with Sr/Ca-derived SST in four corals on the same reef. I show that intercolony disparities in mean Sr/Ca, amplitude of variability, and trend are not due to differences in water temperature, but rather to “vital effects” that result in a ± 2 ̊C uncertainty on reconstructed SST. I then expand, refine, and test a new paleothermometer, Sr-U, across multiple coral species and through time. I show that Sr-U captures spatial SST variability with an uncertainty of ± 0.6 ̊C. When applied to two corals outside of the calibration, Sr-U accurately captures the mean SST and the 20th century trend in the Western Tropical Atlantic. Finally, I apply Sr-U to a coral from the Little Ice Age (LIA) to address uncertainties in the magnitude of western tropical Atlantic cooling during a 95-year period spanning 1465-1560. Results suggest the region was 1.1 ̊C±0.6°C cooler than the 1958-1988 mean, but within error of early 20th century SST at this site. Critically, several periods of warmth, equivalent to the 1958-1988 mean, occurred during a solar minimum that is widely believed to have been a cool period of the LIA. My results indicate that Sr/Ca exaggerates the actual cooling by almost 3 °C. My record demonstrates the value of Sr-U and highlights the need for continuous accurate SST records to better constrain the amplitude, drivers, and mechanisms of LIA tropical climate change.
Book Synopsis Coral Records of Central Tropical Pacific Sea-surface Temperature and Salinity Variability Over the 20th Century by : Intan Suci Nurhati
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.
Book Synopsis Low-latitude Western North Atlantic Climate Variability During the Past Millenium by : Casey Pearce Saenger
Download or read book Low-latitude Western North Atlantic Climate Variability During the Past Millenium written by Casey Pearce Saenger and published by . This book was released on 2009 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Estimates of natural climate variability during the past millennium provide a frame of reference in which to assess the significance of recent changes. This thesis investigates new methods of reconstructing low-latitude sea surface temperature (SST) and hydrography, and combines these methods with traditional techniques to improve the present understanding of western North Atlantic climate variability. A new strontium/calcium (Sr/Ca) - SST calibration is derived for Atlantic Montastrea corals. This calibration shows that Montastrea Sr/Ca is a promising SST proxy if the effect of coral growth is considered. Further analyses of coral growth using Computed Axial Tomography (CAT) imaging indicate growth in Siderastrea corals varies inversely with SST on interannual timescales. A 440-year reconstruction of low-latitude western North Atlantic SST based on this relationship suggests the largest cooling of the last few centuries occurred from ~1650-1730 A.D., and was ~1 °C cooler than today. Sporadic multidecadal variability in this record is inconsistent with evidence for a persistent 65-80 year North Atlantic SST oscillation. Volcanic and anthropogenic radiative forcing are identified as important sources of externally-forced SST variability, with the latter accounting for most of the 20th century warming trend. An 1800-year reconstruction of SST and hydrography near the Gulf Stream also suggests SSTs remained within about 1°C of modern values. This cooling is small relative to other regional proxy records and may reflect the influence of internal oceanic and atmospheric circulation. Simulations with an atmospheric general circulation model (AGCM) indicate that the magnitude of cooling estimated by proxy records is consistent with tropical hydrologic proxy records.
Book Synopsis Pacific Decadal Climate Record Inferred from Instrumental and Coral Data by : Junhua Liu
Download or read book Pacific Decadal Climate Record Inferred from Instrumental and Coral Data written by Junhua Liu and published by . This book was released on 2008 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: We successfully developed a Pacific decadal variation index by combining this core with four published coral records, and a tree ring reconstruction back 270 years. This joint proxy indicates that the present state of the PDO is nearly "neutral", with no significant changes of amplitude, trend, or frequency over the entire record. The stability implies that different feedbacks identified for this mode are not only sufficiently strong to neutralize (so far) the effects of global warming, but that any mechanism proposed to explain the observed stability must be able to account for the changing energy input into the tropical Pacific system from global warming.
Book Synopsis Interannual to Decadal Variability in the Tropical Atlantic by : Dietmar Dommenget
Download or read book Interannual to Decadal Variability in the Tropical Atlantic written by Dietmar Dommenget and published by . This book was released on 1998 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Decadal Variability of the Atlantic Meridional Overturning Circulation by : Martha Weaver Buckley
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.
Book Synopsis A Coral Perspective on Last Interglacial Tropical Atlantic Temperature and Hydroclimate Variability by : William M. Brocas
Download or read book A Coral Perspective on Last Interglacial Tropical Atlantic Temperature and Hydroclimate Variability written by William M. Brocas and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Decadal Variability in the Tropical Atlantic as Simulated by the Climate System Model and CCM3 Coupled to Slab Ocean Model by : Michela Biasutti
Download or read book Decadal Variability in the Tropical Atlantic as Simulated by the Climate System Model and CCM3 Coupled to Slab Ocean Model written by Michela Biasutti and published by . This book was released on 2000 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Coral [delta] 18 O Records from Palau and Eastern Island by : Michael Cleveland Osborne
Download or read book Coral [delta] 18 O Records from Palau and Eastern Island written by Michael Cleveland Osborne and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Coral-based proxy records are one of the most powerful tools for extending our understanding of interannual to centennial modes associated with El Niño-Southern Oscillation (ENSO) variability. Such records are also crucial for constraining forecasts under various greenhouse gas emission scenarios. In this dissertation I present an examination of records obtained from two study sites: The Republic of Palau (7.5°N 134.5°E) and Easter Island (27°S 109°W). This dissertation is organized into five chapters and an appendix. Chapter 1 is an introduction to paleoclimate, ENSO, and coral-based proxy records. In Chapter 2, I present the analysis of four records from Palau that were sampled from diverse localities within this study region. We take advantage of the multiple instrumental products and previously published results in our evaluation of the Palau coral [delta] 18O ([delta] 18OCRL) signal. Our primary conclusion in Chapter 2 is that Palau [delta] 18OCRL is well suited to capture ENSO, regardless of the coral environmental setting. We also show that Palau [delta] 18OCRL is primarily related to salinity, with temperature exerting a secondary influence. In Chapter 3 we apply our [delta] 18OCRL calibration results from Palau to the pre-instrumental period. Our records exhibit excellent reproducibility over the 20th century, and show strong coherence with other tropical Pacific [delta] 18OCRL records. We identify a 23/24 year cycle which is robust throughout the West Pacific Warm Pool (WPWP) following the end of the Little Ice Age (LIA). The Palau records show a long-term trend indicative of warming and/or freshening. Chapter 4 presents the results of three previously unpublished [delta] 18OCRL records from Easter Island, which resides in a region that is particularly devoid of high-resolution paleoclimate observations. All of the Easter Island corals display complex growth morphology. As a result, we deploy a range of techniques to develop age models. Our chief conclusion is that the Easter Island [delta] 18OCRL records closely follow hemispheric and global scale temperature trends over the 20th century. We also observe unique seasonal trends, which are likely attributable biases in seasonal carbonate precipitation and our age model schemes. Our analyses of the Easter Island [delta] 18OCRL records support the assertion that decadal variability across the Pacific basin originates in the tropics. All of the [delta] 18OCRL records presented in this dissertation represent significant contributions our understanding of Pan-Pacific climate variability over the past two centuries.
Book Synopsis Decadal Climate Fluctuations in the Tropical Atlantic Sector by : J. A. Carton
Download or read book Decadal Climate Fluctuations in the Tropical Atlantic Sector written by J. A. Carton and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Decadal- to Century Scale Climate Variability in the Tropical North Atlantic as Recorded in Sediments from the Anoxic Cariaco Basin, Venezuela by : David Edward Black
Download or read book Decadal- to Century Scale Climate Variability in the Tropical North Atlantic as Recorded in Sediments from the Anoxic Cariaco Basin, Venezuela written by David Edward Black and published by . This book was released on 1998 with total page 760 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Low-latitude Western North Atlantic Climate Variability During the Past Millennium by : Casey Pearce Saenger
Download or read book Low-latitude Western North Atlantic Climate Variability During the Past Millennium written by Casey Pearce Saenger and published by . This book was released on 2009 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: (cont.) Simulations with an atmospheric general circulation model (AGCM) indicate that the magnitude of cooling estimated by proxy records is consistent with tropical hydrologic proxy records.
Book Synopsis Tropical Atlantic and Caribbean Climate Variations During the Past Eight Centuries by : Kelly Halimeda Kilbourne
Download or read book Tropical Atlantic and Caribbean Climate Variations During the Past Eight Centuries written by Kelly Halimeda Kilbourne and published by . This book was released on 2006 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work focuses on reconstructing ocean conditions in the northern Caribbean from the geochemistry of corals growing offshore of southwestern Puerto Rico (17.9°N, 67.0°W). Annually resolved records of Sr/Ca and delta 18O were generated for the years 2004 to 1751 from one continuous core. The same annual samples were analyzed for Delta14C between 2004 and 1950, and every 5 years between 1955-1751. Short (14-4 years) monthly-resolved records of delta18O and Sr/Ca were generated from this core and two other cores to investigate the role of seasonal variability during mean climate state variations.
Book Synopsis North Atlantic Ocean Decadal Variability Over the Past Millennium from Climate Model Simulations and Proxy Based Reconstructions by : Maria Pyrina
Download or read book North Atlantic Ocean Decadal Variability Over the Past Millennium from Climate Model Simulations and Proxy Based Reconstructions written by Maria Pyrina and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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