Dissertations / Theses on the topic 'Atmospheric changes'

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Kyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第4973号
理博第1370号
新制||理||765(附属図書館)
UT51-92-J20
京都大学大学院理学研究科地球物理学専攻
(主査)教授 中川 一郎, 教授 田中 寅夫, 教授 住友 則彦
学位規則第4条第1項該当

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 59-60).
A recent article by Kidston et al. [8] demonstrates that the length of atmospheric eddies increases in simulations of future global warming. This thesis expands on Kidston et al.'s work with additional studies of eddy length in the NCEP2 reanalysis (a model-data synthesis that reconstructs past atmospheric circulation) and general circulation models (GCMs) from the Coupled Model Intercomparison Project phase 3. Eddy lengths are compared to computed values of the Rossby radius and the Rhines scale, which have been hypothesized to set the eddy length. The GCMs reproduce the seasonal variation in the eddy lengths seen in the reanalysis. To explore the effect of latent heating on the eddies, a modification to the static stability is used to calculate an effective Rossby radius. The effective Rossby radius is an improvement over the traditional dry Rossby radius in predicting the seasonal cycle of northern hemisphere eddy length, if the height scale used for calculation of the Rossby radius is the depth of the free troposphere. There is no improvement if the scale height is used instead of the free troposphere depth. However, both Rossby radii and the Rhines scale fail to explain the weaker seasonal cycle in southern hemisphere eddy length. In agreement with Kidson et al., the GCMs robustly project an increase in eddy length as the climate warms. The Rossby radii and Rhines scale are also generally projected to increase. Although it is not possible to state with confidence what process ultimately controls atmospheric eddy lengths, taken as a whole the results of this study increase confidence in the projection of future increases in eddy length.
by Todd A. Mooring.
S.B.

In this work over 200 temperature proxy data sets have been analyzed to determine if periodic and or quasi-periodic patterns exist in the data sets. References to the journal articles where data are recorded are provided. Chapter 1 serves an introduction to the problem of temperature determination in providing information on how various proxy data sources are derived. Examples are given of the techniques followed in producing proxy data that predict temperature for each method used. In chapter 2 temperature proxy data spanning the last 4000 years, from 2,000 BCE to 2,000 CE, are analyzed to determine if overarching patterns exist in proxy data sets. An average of over 100 proxy data sets was used to produce Figure 4. An overview of the data shows that several “peaks” can be identified. The data were then subjected to analysis using a series of frequency modulated cosine waves. This analysis led to a function that can be expressed by equation 3. The literature was examined to determine what mathematical models had been published to fit the experimental proxy data for temperature. A number of attempts have been made to fit data from limited data sets with some degree of success. Some other papers have used a sinusoidal function to best fit the changes in the temperature. After consideration of many published papers and reviewing long time streams of proxy data that appeared to have sine wave patterns, a new model was proposed for trial. As the patterns observed showed “almost” repeating sine cycles, a frequency modulated sine wave was chosen to obtain a best fit function. Although other papers have used a sinusoidal function to best fit the changes in the temperature, the “best fit” was limited. Thus, it was decided that a frequency modulated sine wave may be a better model that would provide a more precise fit. This proved to be the case and the more than 240 temperature proxy data sets were analyzed using Equation 3. In chapter 3 the time span for the proxy data was extended to cover the period of time 12,000 BCE to 2000 CE. The data were then tested by using the equation above to search for periodic/quasi-periodic patterns. These results are summarized under select conditions of time periods. In chapter 4 the interval of time is extended over 1,000,000 years of time to test for long period “periodic” changes in global temperature. These results are provided for overall analysis. The function f(x) as described above was used to test for periodic/quasi-periodic changes in the data. Chapter 5 provides an analysis of temperature proxy data for an interval of time of 3,000,000 years to establish how global temperature has varied during the last three million years. Some long-term quasi-periodic patterns are identified. Chapter 6 provides a summation of the model proposed for global temperature that can be expected if similar trends continue over future years as have prevailed for the past few million years. Data sets that were used in this work are tabulated in the appendices of this paper.

In this work over 200 temperature proxy data sets have been analyzed to determine if periodic and or quasi-periodic patterns exist in the data sets. References to the journal articles where data are recorded are provided. Chapter 1 serves an introduction to the problem of temperature determination in providing information on how various proxy data sources are derived. Examples are given of the techniques followed in producing proxy data that predict temperature for each method used. In chapter 2 temperature proxy data spanning the last 4000 years, from 2,000 BCE to 2,000 CE, are analyzed to determine if overarching patterns exist in proxy data sets. An average of over 100 proxy data sets was used to produce Figure 4. An overview of the data shows that several “peaks” can be identified. The data were then subjected to analysis using a series of frequency modulated cosine waves. This analysis led to a function that can be expressed by equation 3. The literature was examined to determine what mathematical models had been published to fit the experimental proxy data for temperature. A number of attempts have been made to fit data from limited data sets with some degree of success. Some other papers have used a sinusoidal function to best fit the changes in the temperature. After consideration of many published papers and reviewing long time streams of proxy data that appeared to have sine wave patterns, a new model was proposed for trial. As the patterns observed showed “almost” repeating sine cycles, a frequency modulated sine wave was chosen to obtain a best fit function. Although other papers have used a sinusoidal function to best fit the changes in the temperature, the “best fit” was limited. Thus, it was decided that a frequency modulated sine wave may be a better model that would provide a more precise fit. This proved to be the case and the more than 240 temperature proxy data sets were analyzed using Equation 3. In chapter 3 the time span for the proxy data was extended to cover the period of time 12,000 BCE to 2000 CE. The data were then tested by using the equation above to search for periodic/quasi-periodic patterns. These results are summarized under select conditions of time periods. In chapter 4 the interval of time is extended over 1,000,000 years of time to test for long period “periodic” changes in global temperature. These results are provided for overall analysis. The function f(x) as described above was used to test for periodic/quasi-periodic changes in the data. Chapter 5 provides an analysis of temperature proxy data for an interval of time of 3,000,000 years to establish how global temperature has varied during the last three million years. Some long-term quasi-periodic patterns are identified. Chapter 6 provides a summation of the model proposed for global temperature that can be expected if similar trends continue over future years as have prevailed for the past few million years. Data sets that were used in this work are tabulated in the appendices of this paper.

Thesis: Ph. D. in Geophysics, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 243-252).
Quantitative measurements of seismic velocity changes from time-lapse seismic experiments provide dynamic information about the subsurface that improves the understanding of the geology and reservoir properties. In this thesis, we propose to achieve the quantitative analysis using full wavefield inversion methods which are robust in complex geology. We developed several methodologies in both the data domain and image domain to handle different time-lapse seismic acquisitions. In the data domain, we implemented double-difference waveform inversion (DDWI), and investigated its robustness and feasibility with realistic acquisition non-repeatabilities. Well-repeated time-lapse surveys from Valhall in the North Sea are used to compare DDWI and conventional time-lapse full waveform inversion (FWI) schemes. An FWI approach that uses the baseline and monitor datasets in an alternating manner is proposed to handle time-lapse surveys without restrictions on geometry repeatability, and to provide an uncertainty analysis on the time-lapse changes. In the image domain, we propose time-lapse image domain wavefield tomography (IDWT) that inverts for P- and S-wave velocity changes by matching baseline and monitor images produced with small offset reflection surveys. This method is robust to survey geometry non-repeatabilities and baseline velocity errors. A low velocity zone caused by local CO2 injections in SACROC, West Texas is found by IDWT with time-lapse walkaway vertical seismic profile surveys. The methods in this thesis combined, allow for an integrated velocity inversion to achieve high-resolution subsurface monitoring with various types of acquisitions in complex geology.
by Di Yang.
Ph. D. in Geophysics

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1993.
Includes bibliographical references (leaves 121-126).
by Alica María Lavín Montero.
M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995.
Includes bibliographical references (leaves 47-49).
by Tavenner Marie Hall.
M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1990.
Archives copy lacks leaf 247.
15 folded maps in pocket.
Includes bibliographical references (leaves 120-140).
by José Wilson Corrêa Rosa.
Ph.D.

It is generally accepted that global levels of CO2 will roughly double over the next century. Because of their large population sizes and fast generation times, microalgae may adapt to global change through novel mutations fixed by natural selection, such that future populations may be genetically different from contemporary ones. The prediction that microalgae may respond evolutionarily to rising CO2 was tested using populations of Chlamydomonas reinhardtii grown for 1000 generations at increasing CO2. Laboratory populations grown at high CO2 did not show a direct response to selection at elevated CO2, instead evolving a range of non-adaptive syndromes. In addition, populations selected at elevated CO2 often grew poorly at ambient CO2. The same evolutionary responses were seen in natural populations isolated from CO2 springs. CO2 uptake was measured in a subset of the laboratory selection lines, which were found to have cells that either leaked CO2, had lost the ability to induce high-affinity CO 2 uptake, or both. These phenotypes were tentatively attributed to the accumulation of conditionally neutral mutations in genes involved in the carbon concentrating mechanism (CCM). The high-CO2-selected phenotypes were found to be reversible in terms of fitness when populations were backselected in air, though wild-type regulation of the CCM was not regained. It has been suggested that phytoplankton adaptation to changes in CO2 levels is constrained by selective history. This was tested by culturing genetically distinct populations of Chlamydomonas at decreasing levels of CO2. In this case, divergence between lines was attributable to chance rather than selective history.

Thesis: S.M. in Geophysics, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 65-69).
Reservoir models use the elastic moduli of rock, both bulk and shear, to compute deformation. These moduli may change with pressure and fracture density, but this effect is usually left out of models. This work shows effective elastic moduli of fluid-filled fractured rock through a self consistent method. The calculated effective elastic moduli for a penny-shaped crack are compared to literature values. Effective moduli values for rocks containing rough fractures with asperities are presented. The bulk and shear moduli increase with external stress. Increases in pore pressure cause an increase in bulk modulus but a decrease in shear modulus. The effect of using these determined effective moduli of fractured rock in modeling is investigated through a model of surface deformation over the In Salah gas reservoir in Algeria where carbon sequestration was performed. The In Salah CO₂ storage project is commonly studied due to the unexpected surface deformation observed. Surface deformation of less than a millimeter occurs from changing the material properties in this reservoir to that of saturated fractured rock containing 25 square rough fractures per cubic meter of 0.2 m side length and 0.22 m aperture, as determined in this study.
by Jamie Potter.
S.M. in Geophysics

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2005.
Includes bibliographical references (p. 63-68).
A combination of bulk carbon, biomarker and compound specific isotopic analyses were used in order to investigate the changes which accompanied the deposition of black shales during the upper tenuicostatum and lower falciferum zones of the Toarcian (early Jurassic, 183 Ma) ocean anoxic event (OAE). In this study, we reveal that apparent negative isotopic excursions in bulk organic and carbonate carbon were the result of compositional changes of organic matter and diagenesis, respectively. Organic petrology and Rock-Eval pyrolysis of organic matter from the Jet Rock, Hawsker Bottoms, Yorkshire, England, show that the upper tenuicostatum zone contains very large amounts of terrigenous debris. A careful review of the carbonate carbon record, as reported in the literature, indicates that a large negative isotopic excursion in bulk carbonate is likely the result of diagenesis, rather than reflective of seawater isotopic conditions. Biomarker distributions and isotopic composition of primary production biomarkers show little variation during the largest changes in the bulk records. Biomarker source indicators vary little throughout the section, indicating little change in biota or redox structure of the water column during this widespread deposition of black shales. Isotopic compositions of algal short chain n-alkanes, pristane and phytane also remain steady across the section.
(cont.) Long chain n-alkanes, biornarkers for higher plants, also do not change during the event. Isorenieratane, a biomarker for green sulphur bacteria and an indicator of photic zone euxinia, however, show a strong peak in concentration coincident with the maximum abundance of organic carbon. Because we have found no evidence for significant isotopic variation on land or in the ocean, we must infer that there were no major redistributions of carbon in the ocean-atmosphere system during the Toarcian OAE. Therefore, oceanic overturn or large input of methane are not plausible explanations for this event. This deposition of black shales was a result of periodic episodic euxinia, which resulted in the increased preservation of organic matter. We believe that this event was not a large, one-time occurrence, but a characteristic response to paleogeography and oceanic circulation patterns of the Mesozoic.
by Alison Margaret Cohen.
S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 59-60).
This study investigates recent changes in the variability and seasonality of temperature and precipitation in the Northern Hemisphere. The mean and variance of daily temperature and precipitation anomalies are calculated for each year over a 35-year period and compared to a base period. For temperature in the Northern Hemisphere, a noticeable warming trend amplified in the higher latitudes was observed, as well as a significant decrease in variability in the mid and high latitudes. For precipitation in the Northern Hemisphere, a drying trend and decreasing trend in variability were observed in the mid latitudes during summer. The seasonal cycles of both temperature and precipitation were also analyzed. The trends in temperature seasonal amplitude and phase were studied and revealed some influence of Arctic sea ice loss that changes the seasonality of local temperature, and Arctic amplification that potentially influences temperature seasonality in the mid and high latitude land regions. To determine whether the changes in temperature seasonality may affect temperature variance, analyses were performed by removing the phase trends from the temperature data using two methods. The phase trend-removed temperatures were found to have no prominent trends in variance. This suggests that changes in the temperature variance may be related to changes in temperature seasonality. To study what affects precipitation variability, the coefficient of variation (ratio of standard deviation to mean), which determines the shape of the mixed gamma probability distribution function (PDF) of precipitation, was studied. It was found that the mean and variance of precipitation have a fixed ratio over time, suggesting that the shape of the precipitation PDF has not changed. Therefore changes in the precipitation variance in the midlatitudes could be simply explained by the change in the mean precipitation in the same region.
by Katrina L. Hui.
S.B.

The climate over Ecuador is complex due to several interacting factors, such as its location at the equator, the Andean topography, and several modes of internal variability, including the El Niño–Southern Oscillation (ENSO), affecting the region. In addition, the rapid increase in greenhouse gas concentrations will continue to affect both the mean state and climate variability in Ecuador over the coming decades. Hence, a thorough understanding of both natural and anthropogenic forcings and how they combine to influence Ecuadorian climate is a necessity for decision-making and implementation of adequate adaptation measures. However, the lack of observational data, both in space and time, severely limits our ability to study climate changes that affect Ecuador today. Employing a high-resolution regional climate model (RCM) can help to better diagnose the mechanisms and feedbacks that lead to climate changes and how they differ in space and time, as long as the model is able to adequately reproduce what is observed in the limited observational data.

With the purpose of contributing to a better understanding of how and why Ecuador’s climate will change in the coming decades, three topics of specific relevance for this country are addressed in this dissertation: a) how well can a RCM simulate the mean climate state and its variability over a region of complex topography such as Ecuador under different parameterization schemes? b) what feedbacks are involved in producing elevation-dependent warming (EDW) in the Ecuadorian Andes? And c) how are the characteristics of climate extreme events (CEEs) over Ecuador projected to change by the middle of the 21st century? These three questions are addressed by use of observations and simulations using the Weather Research and Forecasting Model (WRF) configured as a RCM with a high-resolution of 10 km horizontal grid spacing and 51 vertical levels.

Sensitivity test runs were performed to choose a proper combination of parameterization schemes for conducting four WRF simulations comprising the territory of Ecuador and spanning 30 years. The first simulation was driven by the Climate Forecast System Reanalysis (CFSR) for the period 1980–2010 and used to evaluate the model’s ability to realistically portray present-day climate over the region. The other three simulations used the output from the Community Climate System Model version 4 (CCSM4) as the boundary conditions to produce a baseline simulation (1976–2005) and two future simulations (2041– 2070) following the moderate-emissions scenario RCP 4.5 and the high-emissions scenario RCP 8.5.

EDW over the Ecuadorian Andes is studied by analyzing observations and the present-day WRF-simulation, while the future simulations were used to test the contribution to this effect caused by future changes in feedback mechanisms. Surface net radiation changes due to future changes in cloudiness were identified as the most important mechanisms leading to EDW over the Ecuadorian Andes, with future reductions in cloudiness dominating at high elevations. The model results also indicate different future warming signals on both sides of the Andes, with higher warming rates at the high elevations of the western Andes, likely due to enhanced subsidence and adiabatic warming in the mid-troposphere.

CEEs are analyzed by using annual climatic indices. First the present-day relationship between CEEs and Pacific (ENSO) and Atlantic modes of variability are investigated in both models and observations. Results confirm the dominant role played by ENSO in governing the occurrence of many CCEs over Ecuador, while calling for more studies on the potential influence of Atlantic modes over Ecuador’s CEEs. The model projections suggest significant future changes in CEEs, with large increases in warm and wet extremes over most regions, but the simulations also highlight significant spatial heterogeneity, which suggests that it is important to study changes in extreme events using high-spatial resolution data.

Atmospheric aerosols are known to exert a significant influence on the Earth's climate system; however, the magnitude of this influence is highly uncertain because of the complex interaction between aerosols and water vapor to form clouds. Toward reducing this uncertainty, this dissertation outlines a series of laboratory and in-situ field measurements, instrument technique development, and model simulations designed to characterize the ability of aerosols to act as cloud condensation nuclei (CCN) and form cloud droplets. Specifically, we empirically quantify the mixing state and thermodynamic properties of organic aerosols (e.g., hygroscopicity and droplet condensational uptake coefficient) measured in polluted and non-polluted environments including Alaska, California, and Georgia. It is shown that organic aerosols comprise a substantial portion of the aerosol mass and are often water soluble. CCN measurements are compared to predictions from theory in order to determine the error associated with simplified composition and mixing state assumptions employed by current large-scale models, and these errors are used to constrain the uncertainty of global and regional cloud droplet number and albedo using a recently-developed cloud droplet parameterization adjoint coupled with the GMI chemical transport model. These sensitivities are important because they describe the main determinants of climate forcing. We also present two novel techniques for fast measurements of CCN concentrations with high size, supersaturation, and temporal resolution that substantially improve the state of the art by several orders of magnitude. Ultimately, this work represents a step toward better understanding how atmospheric aerosols influence cloud properties and Earth's climate.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989.
Includes bibliographical references (p. 227-239).
by Arlindo Moraes da Silva, Jr.
Ph.D.

Diss. (sammanfattning) Stockholm : Stockholms universitet, 2009.
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: In press. Paper 2: Submitted. Paper 5: In progress.

Simulations alternatively assuming a landscape with and without urbanization plus open-cast mining were performed with a non-hydrostatic model. lt is examined whether the atmospheric response to landuse changes is sensitive to the direction of the geostrophic wind. The results of simulations with the same geostrophic wind direction show that except for the cloud and precipitating particles the daily domain-averages of the variables of state hardly differ for the different landscapes. Nevertheless, the local weather may be affected appreciably over and downwind of the altered surfaces. The significant differences in the cloud and precipitating particles, however, are not bound to the environs of the landuse changes. Generally, the most significant differences occur for the cloud and precipitation particles, the soil wetness factors and the vertical component of the wind vector. The latter changes strongly influence the cloud and precipitation formation by the interaction cloud microphysics-dynamics. The results also indicate that for most of the quantities the local magnitude of the atmospheric response changes for the various directions of the geostrophic wind. However, the differences of the domain-averaged 24h-accumulated evapotranspiration are similar for all geostrophic wind directions
Um zu untersuchen, ob die atmosphärische Antwort auf Landnutzungsänderungen sensitiv zur Richtung des geostrophischen Windes ist, wurden Simulationen durchgeführt, bei denen alternativ eine Landschaft mit und ohne Urbanisierung plus Tagebauten angenommen wurde. Die Simulationsergebnisse zeigen, daß - außer für Wolken- und Niederschlagspartikel - die täglichen Gebietsmittelwerte der Zustandsvariablen sich kaum für die beiden Landschaften unterscheiden. Trotzdem kann das lokale Wetter merklich über und im Lee der Oberflächen mit veränderter Landnutzung beeinflußt werden. Die signifikanten Differenzen in den Wolken- und Niederschlagspartikeln sind jedoch nicht an die unmittelbare Nähe der Landnutzungsänderungen gebunden. Generell treten die signifikanten Unterschiede bei den Wolkenund Niederschlagspartikeln, der Bodenfeuchte und der Vertikalkomponente des Windvektors auf. Letztere beeinflussen stark die Wolken- und Niederschlagsbildung durch die Wechselwirkung Wolkenmikrophysik-Dynamik. Die Ergebnisse zeigen außerdem, daß lokal der Grad der atmosphärischen Reaktion für die meisten Größen bei unterschiedlicher Richtung des geostrophischen Windes anders ausfällt. Die Differenzen der Gebietsmittelwerte der 24h-akkumulierten Evapotranspiration gleichen sich jedoch für alle Richtungen des geostrophischen Windes

Simulations alternatively assuming a landscape with and without urbanization plus open-cast mining were performed with a non-hydrostatic model. lt is examined whether the atmospheric response to landuse changes is sensitive to the direction of the geostrophic wind. The results of simulations with the same geostrophic wind direction show that except for the cloud and precipitating particles the daily domain-averages of the variables of state hardly differ for the different landscapes. Nevertheless, the local weather may be affected appreciably over and downwind of the altered surfaces. The significant differences in the cloud and precipitating particles, however, are not bound to the environs of the landuse changes. Generally, the most significant differences occur for the cloud and precipitation particles, the soil wetness factors and the vertical component of the wind vector. The latter changes strongly influence the cloud and precipitation formation by the interaction cloud microphysics-dynamics. The results also indicate that for most of the quantities the local magnitude of the atmospheric response changes for the various directions of the geostrophic wind. However, the differences of the domain-averaged 24h-accumulated evapotranspiration are similar for all geostrophic wind directions.
Um zu untersuchen, ob die atmosphärische Antwort auf Landnutzungsänderungen sensitiv zur Richtung des geostrophischen Windes ist, wurden Simulationen durchgeführt, bei denen alternativ eine Landschaft mit und ohne Urbanisierung plus Tagebauten angenommen wurde. Die Simulationsergebnisse zeigen, daß - außer für Wolken- und Niederschlagspartikel - die täglichen Gebietsmittelwerte der Zustandsvariablen sich kaum für die beiden Landschaften unterscheiden. Trotzdem kann das lokale Wetter merklich über und im Lee der Oberflächen mit veränderter Landnutzung beeinflußt werden. Die signifikanten Differenzen in den Wolken- und Niederschlagspartikeln sind jedoch nicht an die unmittelbare Nähe der Landnutzungsänderungen gebunden. Generell treten die signifikanten Unterschiede bei den Wolkenund Niederschlagspartikeln, der Bodenfeuchte und der Vertikalkomponente des Windvektors auf. Letztere beeinflussen stark die Wolken- und Niederschlagsbildung durch die Wechselwirkung Wolkenmikrophysik-Dynamik. Die Ergebnisse zeigen außerdem, daß lokal der Grad der atmosphärischen Reaktion für die meisten Größen bei unterschiedlicher Richtung des geostrophischen Windes anders ausfällt. Die Differenzen der Gebietsmittelwerte der 24h-akkumulierten Evapotranspiration gleichen sich jedoch für alle Richtungen des geostrophischen Windes.

Observations of atmospheric gas concentrations are very useful in the study of globally important ecosystems. Past observational efforts, however, have been focused on atmospheric measurements of ‘background air’, leaving the continental interiors under-represented. I present results from pilot, multi-species, atmospheric measurement campaigns in the Hainich Forest, Germany in 2005, and I describe the development, deployment, and results from high-precision continuous atmospheric measurements of CO2, O2, CH4, CO and N2O at the Zotino Tall Tower Observatory (ZOTTO) in the boreal forest of central Siberia from November 2005 to June 2007. Atmospheric variations were studied on seasonal, synoptic and diurnal time scales. Among the interesting features of the ZOTTO record are: 1) CO2 and O2 seasonal amplitudes of 26.6 ppm and 190 per meg (equivalent to 39.8 ppm in CO2); 2) a west-east gradient of –7 ppm of CO2 (in July 2006) between Shetland Islands (Scotland) and ZOTTO that reflects summertime continental CO2 uptake; 3) attenuation of the oceanic component of the O2 seasonal amplitude (Atmospheric Potential Oxygen; APO) at ZOTTO resulting in an amplitude of 45 per meg compared to 56 per meg observed at Shetlands; 4) high fire emissions of CH4 and CO in summertime with the minima of their monthly averages similar to seasonal cycles of these gases in the marine boundary layer; 5) large vertical gradients in CO2, CH4 and CO during ‘cold events’ (air temperatures below -30°C), suggesting separated layers of air and local sources possibly combined with other effects; 6) lower CO/CO2 ratios (1-4 ppb/ppm) from fossil fuel burning compared to those measured in Europe, with large CH4 contributions; 7) diurnal vertical CO2 gradients in spring 2007 giving estimates of night-time respiration fluxes of 0.04±0.02 mol C m-2 d-1. A comparison with REgional MOdel (REMO) simulations showed discrepancies in daily averages of CO2 attributed to errors in the model’s vertical mixing and prescribed terrestrial fluxes. Nevertheless, REMO exhibited good agreement in meteorological variables (compared to weather stations close to ZOTTO) and seasonal cycles of CO2, APO and CO. Studies of fire events showed high emission ratios of CO/CO2 and CH4/CO2, comparable with those reported for similar ecosystems, and in relatively good agreement with the model estimates.

As we have become more aware of the value of vegetation in the stabilization of coastal sand dunes, there has been an increasing desire to protect valuable native species in coastal habitats. In Florida, introduced exotic species have tended to crowd and eventually replace native vegetation, resulting in the establishment of monocultures. The Australian pine (Casuarina eguisetifolia) introduced to south Florida in 1898 by Fairchild, has become a weed species on beaches, supressing the native grasses associated with dune formation by its exudation of allelopathic substances. A Casuarina eradication project in Jupiter Island (Martin County), Florida was conducted in an attempt to slow beach erosion by allowing reestablishment of native dune forming grasses. Empirical data was obtained from this area to determine: 1. the effects of the loss of a dominant tree species, 2. the changing of the floristics of the area demonstrating subsequent growth of native vegetation, 3. the species reactions to different degrees of soil's salinity and pH. Throughout the study area (Casuarina stand), the elimination of Casuarina resulted in an immediate growth of four species (Ipomoea pes-caprae –railroad vine, Paspalum vaginatum -salt joint grass, Panicum amarulum -panic grass, Uniola paniculata -sea oats ). I. pes-caprae is an opportunistic species representing an early stage of succession while P. vaginatum, P. amarulum, and U. paniculata are members of the climax community. Diversity indices declined after Casuarina eradication due to the initial rapid growth of I. pes-caprae, however significant linear or exponential growth of the native grasses was observed. It was found that the growth rates vary significantly with season. Away from the immediate shore line, maximum growth for all species occurred from mid to late summer. Highest growth rates for the majority of species occurred on a nearby natural dune (control) site, except for two species (I. pes-caprae and P. vaginatum) which were found to be most abundant throughout the (Casuarina stand) disturbed site.

Recent years witnessed a vast advent of stalagmites as palaeoclimate archives. The multitude of geochemical and physical proxies and a promise of a precise and accurate age model greatly appeal to palaeoclimatologists. Although substantial progress was made in speleothem-based palaeoclimate research and despite high-resolution records from low-latitudinal regions, proving that palaeo-environmental changes can be archived on sub-annual to millennial time scales our comprehension of climate dynamics is still fragmentary. This is in particular true for the summer monsoon system on the Indian subcontinent. The Indian summer monsoon (ISM) is an integral part of the intertropical convergence zone (ITCZ). As this rainfall belt migrates northward during boreal summer, it brings monsoonal rainfall. ISM strength depends however on a variety of factors, including snow cover in Central Asia and oceanic conditions in the Indic and Pacific. Presently, many of the factors influencing the ISM are known, though their exact forcing mechanism and mutual relations remain ambiguous. Attempts to make an accurate prediction of rainfall intensity and frequency and drought recurrence, which is extremely important for South Asian countries, resemble a puzzle game; all interaction need to fall into the right place to obtain a complete picture. My thesis aims to create a faithful picture of climate change in India, covering the last 11,000 ka. NE India represents a key region for the Bay of Bengal (BoB) branch of the ISM, as it is here where the monsoon splits into a northwestward and a northeastward directed arm. The Meghalaya Plateau is the first barrier for northward moving air masses and receives excessive summer rainfall, while the winter season is very dry. The proximity of Meghalaya to the Tibetan Plateau on the one hand and the BoB on the other hand make the study area a key location for investigating the interaction between different forcings that governs the ISM. A basis for the interpretation of palaeoclimate records, and a first important outcome of my thesis is a conceptual model which explains the observed pattern of seasonal changes in stable isotopes (d18O and d2H) in rainfall. I show that although in tropical and subtropical regions the amount effect is commonly called to explain strongly depleted isotope values during enhanced rainfall, alone it cannot account for observed rainwater isotope variability in Meghalaya. Monitoring of rainwater isotopes shows no expected negative correlation between precipitation amount and d18O of rainfall. In turn I find evidence that the runoff from high elevations carries an inherited isotopic signature into the BoB, where during the ISM season the freshwater builds a strongly depleted plume on top of the marine water. The vapor originating from this plume is likely to memorize' and transmit further very negative d18O values. The lack of data does not allow for quantication of this plume effect' on isotopes in rainfall over Meghalaya but I suggest that it varies on seasonal to millennial timescales, depending on the runoff amount and source characteristics. The focal point of my thesis is the extraction of climatic signals archived in stalagmites from NE India. High uranium concentration in the stalagmites ensured excellent age control required for successful high-resolution climate reconstructions. Stable isotope (d18O and d13C) and grey-scale data allow unprecedented insights into millennial to seasonal dynamics of the summer and winter monsoon in NE India. ISM strength (i. e. rainfall amount) is recorded in changes in d18Ostalagmites. The d13C signal, reflecting drip rate changes, renders a powerful proxy for dry season conditions, and shows similarities to temperature-related changes on the Tibetan Plateau. A sub-annual grey-scale profile supports a concept of lower drip rate and slower stalagmite growth during dry conditions. During the Holocene, ISM followed a millennial-scale decrease of insolation, with decadal to centennial failures resulting from atmospheric changes. The period of maximum rainfall and enhanced seasonality corresponds to the Holocene Thermal Optimum observed in Europe. After a phase of rather stable conditions, 4.5 kyr ago, the strengthening ENSO system dominated the ISM. Strong El Nino events weakened the ISM, especially when in concert with positive Indian Ocean dipole events. The strongest droughts of the last 11 kyr are recorded during the past 2 kyr. Using the advantage of a well-dated stalagmite record at hand I tested the application of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to detect sub-annual to sub-decadal changes in element concentrations in stalagmites. The development of a large ablation cell allows for ablating sample slabs of up to 22 cm total length. Each analyzed element is a potential proxy for different climatic parameters. Combining my previous results with the LAICP- MS-generated data shows that element concentration depends not only on rainfall amount and associated leaching from the soil. Additional factors, like biological activity and hydrogeochemical conditions in the soil and vadose zone can eventually affect the element content in drip water and in stalagmites. I present a theoretical conceptual model for my study site to explain how climatic signals can be transmitted and archived in stalagmite carbonate. Further, I establish a first 1500 year long element record, reconstructing rainfall variability. Additionally, I hypothesize that volcanic eruptions, producing large amounts of sulfuric acid, can influence soil acidity and hence element mobilization.
Stalagmiten erfuhren in den letzten Jahren vermehrt Aufmerksamkeit als bedeutende Paläoklima- Archive. Paläoklimatologen sind beeindruckt von der grossen Zahl geochemischer und physikalischer Indikatoren (Proxies) und der Möglichkeit, präzise absolute Altersmodelle zu erstellen. Doch obwohl substantielle Fortschritte in der speleothem-basierten Klimaforschung gemacht wurden, und trotz hochaufgelöster Archive aus niederen Breiten, welche zeigen, das Umweltveränderungen auf Zeitskalen von Jahren bis Jahrtausenden archiviert und rekonstruiert werden können, bleibt unser Verständnis der Klimadynamik fragmentarisch. Ganz besonders gilt dies für den Indischen Sommermonsun (ISM) auf dem Indischen Subkontinent. Der ISM ist heute als ein integraler Bestandteil der intertropischen Konvergenzzone verstanden. Sobald dieser Regengürtel während des borealen Sommer nordwärts migriert kann der ISM seine feuchten Luftmassen auf dem Asiatischen Festland entladen. Dabei hängt die Stärke des ISM von einer Vielzahl von Faktoren ab. Zu diesen gehören die Schneedicke in Zentralasien im vorhergehenden Winter und ozeanische Bedingungen im Indischen und Pazifschen Ozean. Heute sind viele dieser Faktoren bekannt. Trotzdem bleiben deren Mechanismen und internen Verbindungen weiterhin mysteriös. Versuche, korrekte Vorhersagen zu Niederschlagsintensität und Häufigkeit oder zu Dürreereignissen zu erstellen ähneln einem Puzzle. All die verschiedenen Interaktionen müssen an die richtige Stelle gelegt werden, um ein sinnvolles Bild entstehen zu lassen. Meine Dissertation versucht, ein vertrauenswürdiges Bild des sich wandelnden Holozänen Klimas in Indien zu erstellen. NE Indien ist eine Schlüsselregion für den östlichen Arm des ISM, da sich hier der ISM in zwei Arme aufteilt, einen nordwestwärts und einen nordostwärts gerichteten. Das Meghalaya Plateau ist das erste Hindernis für die sich nordwärts bewegenden Luftmassen und erhält entsprechend exzessive Niederschläge während des Sommers. Die winterliche Jahreszeit dagegen ist sehr trocken. Die Nähe zum Tibetplateau einerseits und der Bucht von Bengalen andererseits determinieren die Schlüsselposition dieser Region für das Studium der Interaktionen der den ISM beeinflussenden Kräfte. Ein Fundament für die Interpretation der Paläoklimarecords und ein erstes wichtiges Ergebnis meiner Arbeit ist ein konzeptuelles Modell, welches die beobachteten saisonalen Veränderungen stabiler Isotope (d18O und d2H) im Niederschlag erklärt. Ich zeige, das obwohl in tropischen und subtropischen Regionen meist der amount effect zur Erklärung stark negativer Isotopenwerte während starker Niederschläge herangezogen wird, dieser allein nicht ausreicht, um die Isotopenvariabilität im Niederschlag Meghalaya's zu erklären. Die Langzeitbeobachtung der Regenwasserisotopie zeigt keine negative Korrelation zwischen Niederschlagsmenge und d18O. Es finden sich Hinweise, das der Abfluss aus den Hochgebirgsregionen Tibets und des Himalaya eine Isotopensignatur an das Oberflächenwasser der Bucht von Bengalen vererbt. Dort bildet sich aus isotopisch stark abgereicherten Wässern während des ISM eine Süsswasserlinse aus. Es ist wahrscheinlich, das Wasserdampf, der aus dieser Linse stammt, ein Isotopensignal aufgeprägt bekommt, welches abgereichertes d18O weitertransportiert. Der Mangel an Daten lässt es bisher leider nicht zu, quantitative Aussagen über den Einfluss dieses plume effect' auf Niederschläge in Meghalaya zu treffen. Es lässt sich allerdings vermuten, das dieser Einfluss auf saisonalen wie auch auf langen Zeitskalen variabel ist, abhängig vom Abfluss und der Quellencharacteristik. Der Fokus meiner Arbeit liegt in der Herauslösung klimatischer Signale aus nordostindischen Stalagmiten. Hohe Urankonzentrationen in diesen Stalagmiten erlaubt eine exzellente Alterskontrolle, die für hochauflösende Klimarekonstruktionen unerlässlich ist. Die stabilen Isotope (d18O und d13C), sowie Grauwertdaten, erlauben einmalige Einblicke in die Dynamik des Sommer und auch des Wintermonsun in NE Indien. Die ISM Stärke (d. h. Niederschlagsmenge) wird in Veränderungen in den d18Ostalagmites reflektiert. Das d13C Signal, welches Tropfratenänderungen speichert, dient als potenter Indikator für winterliche Trockenheitsbedingungen. Es zeigt Ähnlichkeit zu temperaturabhängigen Veränderungen auf dem Tibetplateau. Das sub-annuell aufgelöste Grauwertprofil stärkt das Konzept, das verminderte Tropfraten und langsameres Stalagmitenwachstum eine Folge von Trockenheit sind. Während des Holozäns folgte der ISM der jahrtausendelangen Verringerung der Insolation. Es finden sich aber ebenso rapide Anomalien, die aus atmosphärischen Veränderungen resultieren. Die Phase des höchsten Niederschlages und erhöhter Saisonalität korrespondiert mit dem Holozänen Thermalen Maximum. Nach einer Phase einigermassen stabilen Bedingungen begann vor ca. 4500 Jahren ENSO einen zunehmenden Einfluss auf den ISM auszuüben. Starke El Nino Ereignisse schwächen den ISM, besonders wenn diese zeitgleich mit positiven Indian Ocean Dipole Ereignissen auftreten. Die stärksten Dürren des gesamten Holozäns traten in den letzten 2000 Jahren auf. Um zusätzliche Informationen aus den hervorragenden Proben zu gewinnen nutzte ich die Vorteile der laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Diese erlaubt die Detektion sub-annueller bis sub-dekadischer Elementkonzentrationsveränderungen in Stalagmiten. Mittels einer neu entwickelten Ablationszelle konnten Proben von maximal 22 cm Länge untersucht werden. Jedes analysierte Element ist ein potentieller Träger einer Klimainformation. Die Kombination der früheren Ergebnisse mit denen der LA-IPC-MS zeigt, das die Elementkonzentrationen nicht nur von Niederschlagsveränderungen und assoziiertem Auswaschen aus dem Boden abhängen. Zusätzlich können auch die biologische Aktivität und hydrogeochemische Bedingungen in der vadosen Zone Einfluss auf die Elementzusammensetzung im Tropfwasser und in den Stalagmiten haben. Darum entwickelte ich ein theoretisches Modell für meinen Standort, um zu klären, wie Klimasignale von der Atmosphäre in die Höhle transportiert werden können. Ein anschliessend rekonstruierter 1500 Jahre langer Proxyrecord zeigt Niederschlagsvariabilität an. Zudem besteht die Möglichkeit, das Vulkaneruptionen, welche grosse Mengen an Schwefelsäure produzieren, eine Bodenversauerung verursachen und damit die Elementmobilisierung verstärken können.

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Impacts of ocean heat content (OHC) and vertical wind shear on intensity changes of Typhoon Sinlaku and Typhoon Jangmi during the Tropical Cyclone Structure-2008 and THORPEX Pacific Asian Regional Campaign are investigated. Observations of ocean structure variables were obtained in the environment of each typhoon via aircraft-deployed expendable bathythermographs (AXBTs). Strong correspondence among storm intensity changes, ocean features, and vertical wind shear is identified as each tropical cyclone passed over regions of warm and cold ocean features with varying vertical wind shears. Typhoon Sinlaku passed over a cold ocean and with a consistently low vertical wind shear, the storm did not intensify for 12 hours. Sinlaku then reached maximum intensity as it passed over a warm ocean feature while vertical wind shear remained low. Sinlaku also weakened as it passed over an intense cold eddy at a time when vertical wind shear was increasing. Similar impacts are defined for TY Jangmi. Comparison of the AXBT profiles with the East Asian Sea Nowcast/Forecast System (EASNFS) analyses consistently indicated the EASNFS mixed layer depths (MLD) were too shallow, had steeper slopes in the thermocline, and a warm sea-surface temperature (SST) bias. The MLD and SST biases compensated causing OHC differences to be reduced.

The influence of anthropogenic emissions on aerosol distributions and the hydrological cycle are examined with a focus on monsoon precipitation over the Indian subcontinent, during January 2001 to December 2005, using the European Centre for Medium-Range Weather Forecasts-Hamburg (ECHAM5.5) general circulation model extended by the Hamburg Aerosol Module (HAM). The seasonal variability of aerosol optical depth (AOD) retrieved from the MODerate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellite is broadly well simulated (R 0.6–0.85) by the model. The spatial distribution and seasonal cycle of the precipitation observed over the Indian region are reasonably well simulated (R 0.5 to 0.8) by the model, while in terms of absolute magnitude, the model underestimates precipitation, in particular in the south-west (SW) monsoon season. The model simulates significant anthropogenic aerosol-induced changes in clear-sky net surface solar radiation (dimming greater than -7 W m-2), which agrees well with the observed trends over the Indian region. A statistically significant decreasing precipitation trend is simulated only for the SWmonsoon season over the central-north Indian region, which is consistent with the observed seasonal trend over the Indian region. In the model, this decrease results from a reduction in convective precipitation, where there is an increase in stratiform cloud droplet number concentration (CDNC) and solar dimming that resulted from increased stability and reduced evaporation. Similarities in spatial patterns suggest that surface cooling, mainly by the aerosol indirect effect, is responsible for this reduction in convective activity. When changes in large-scale dynamics are allowed by slightly disturbing the initial state of the atmosphere, aerosol absorption in addition leads to a further stabilization of the lower troposphere, further reducing convective precipitation.

The influence of anthropogenic emissions on aerosol distributions and the hydrological cycle are examined with a focus on monsoon precipitation over the Indian subcontinent, during January 2001 to December 2005, using the European Centre for Medium-Range Weather Forecasts-Hamburg (ECHAM5.5) general circulation model extended by the Hamburg Aerosol Module (HAM). The seasonal variability of aerosol optical depth (AOD) retrieved from the MODerate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellite is broadly well simulated (R 0.6–0.85) by the model. The spatial distribution and seasonal cycle of the precipitation observed over the Indian region are reasonably well simulated (R 0.5 to 0.8) by the model, while in terms of absolute magnitude, the model underestimates precipitation, in particular in the south-west (SW) monsoon season. The model simulates significant anthropogenic aerosol-induced changes in clear-sky net surface solar radiation (dimming greater than -7 W m-2), which agrees well with the observed trends over the Indian region. A statistically significant decreasing precipitation trend is simulated only for the SWmonsoon season over the central-north Indian region, which is consistent with the observed seasonal trend over the Indian region. In the model, this decrease results from a reduction in convective precipitation, where there is an increase in stratiform cloud droplet number concentration (CDNC) and solar dimming that resulted from increased stability and reduced evaporation. Similarities in spatial patterns suggest that surface cooling, mainly by the aerosol indirect effect, is responsible for this reduction in convective activity. When changes in large-scale dynamics are allowed by slightly disturbing the initial state of the atmosphere, aerosol absorption in addition leads to a further stabilization of the lower troposphere, further reducing convective precipitation.

Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 28-29).
Recent work by Santer et al. (2018) in Science examined the usefulness of the latitudinal structure and seasonal behavior of warming for fingerprinting anthropogenic climate change using satellite data and the CMIP5 multi-model ensemble over 1979-2016. They identify the first seasonal fingerprint in the northern hemisphere annual cycle and structure of warming, but do not specify what forcing agent (e.g. ozone, soot, or greenhouse gases) is responsible for causing it. We further probe this phenomena using 3 ensembles-of-opportunity over 1955-1979 and 1995-2024 of the Whole Atmosphere Community Climate Model version 4 (WACCM4), one of the world's few best fully coupled interactive chemistry-climate models. While our ensembles' construction covers limited time periods, it has the advantage of avoiding the effects of El Chichón (1982) and Pinatubo (1991), which are difficult to capture in models and have different drivers (volcanic) than the ones of interest here. The key findings of this research are that added greenhouse gas forcings nearly fully determine the latitudinal structure of warming and change in the amplitude of the annual cycle, that WACCM4 does a much better job than the CMIP5 multi-model ensemble of predicting the magnitude and latitudinal structure of climate change, and that tropical expansion and a poleward shift of the jet may drive the key subtropical features Santer observed. Interactive chemistry is not found to be a defining factor in representing the rate and structure of warming in CMIP5, and is certainly much less important than other details of model construction.
by Jordan T. Benjamin.
S.B.
S.B. Massachusetts Institute of Technology, Department of Physics

xv, 165 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
The amount of solar radiation at the earth's surface is modulated by fluctuations in aerosol density and cloud optical depth--two uncertain factors in climate change studies. The University of Oregon Solar Radiation Monitoring Lab has collected five-minute resolution surface shortwave irradiance measurements at three sites in Oregon since 1980 or earlier. Direct normal surface solar irradiance has increased 4-5% per decade (8-11 W/m 2 per decade) at these three sites since 1980 (1979 in Eugene). Total solar irradiance has likewise increased by 1-2% per decade (2-3 W/m 2 per decade). This unusually long direct normal time series was used to examine the causes of trends because of its high sensitivity to scattering and high instrumental accuracy. The strongest factor causing direct normal irradiance trends was found to be the high stratospheric aerosol concentrations after the volcanic eruptions of El Chichà à à à ³n (1982) and Mt. Pinatubo (1991). Removing the four years most impacted by each volcanic eruption (1982-1985 and 1991-1994) reduces the trend in annual average direct normal irradiance by 20-55%, depending on the site. All measurement sites show low irradiance values before the volcanic eruption of El Chichà à à à ³n in 1982 compared to later periods of relatively low volcanic aerosols (1989- 1990, and 2000-2007). These low values are visible both in all-sky and clear-sky monthly averages, suggesting high aerosol loads as a likely cause. Clear-sky direct normal irradiance measurements from high solar zenith angles (6575à à à à °) are analyzed to test the hypothesis that the increase in irradiance comes from a reduction of anthropogenic aerosols since the late 1980s. No change in anthropogenic aerosols between 1987 and 2007 is detectable within the noise of the data. Even after removing the four years most heavily impacted by volcanic eruptions, the continued reduction of volcanic aerosol loads causes over half of the clear-sky direct normal irradiance increase since 1987. The remaining increase could be accounted for by a 20-year decrease in 550 nm aerosol optical depth of .005 à à à à ± .005, or 6% à à à à ± 6%, but considerable statistical uncertainty exists.
Adviser: Gregory Bothun

Global mean surface temperatures (GMST) warmed in the early 20th century, experienced a mid-century lull, and warmed again steadily until 1997. Observations at the turn of the 21st century have revealed another period of quiescent warming of GMSTs from 1998 to 2012, thus prompting the notion of a global warming “hiatus”. The warming hiatus occurred concurrently with steadily increasing atmospheric greenhouse gas concentrations, sea level rise, and retreating arctic sea ice. The occurrence of the warming hiatus suggests that natural variability continues to be a sizable contributor to modern climate change and implies that energy is rearranged or changed within the climate system. Much of the scientific research conducted over the last decade has attempted to identify which modes of natural variability may be contributing to the GMST signal in the presence of anthropogenic warming. Many of these studies concluded that natural variability, operating in the global oceans were the largest contributors to GMST. What remains unclear is how oceanic variability and its contribution to GMST may change on a warmer globe as greenhouse gas concentrations continue to rise. Our research includes diagnostic analyses of the available observational surface temperature estimates and novel state-of-the-art climate model experiments from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Our analyses seek to understand how the natural modes of variability within the ocean will change under different warming scenarios. Utilizing simulations forced with observed pre-industrial and historical greenhouse gas emissions in combination with several future warming simulations, we quantify the probability of similar “hiatus-like” periods occurring on a warmer globe. To that end employ various metrics and detrending techniques including EOF decomposition, running climatologies, along with linear and nonlinear trends to elucidate how natural variability changes over time. We also examine the changing influence of natural modes of variability with respect to the anthropogenic radiative forcing over different regions on the globe.Results suggest that natural variability for much of the global oceans decreases as the radiative forcing increases in the future warming scenarios.