Dissertations / Theses on the topic 'Ocean-atmospheric modelling'

Bibliography: leaves 146-155.
Sea surface temperature (SSTs) variations in the South Indian Ocean have been found to influence rainfall over Southern Africa. As one of the modes of South Indian Ocean SST variability, the subtropical South Indian Ocean dipole is observed to be associated with dry and wet summer conditions over Southern Africa. The positive phase of the subtropical South Indian Ocean dipole is characterized by warm SST anomalies in the southwest South Indian Ocean and cool SST anomalies in the southeast. This phase is associated with above average summer rainfall over the subcontinent. The negative phase is associated with dry conditions over Southern Africa and is characterized by cool SST anomalies in the southwest and warm anomalies in the southeast South Indian Ocean. In order to investigate the atmospheric response over Southern Africa to this phenomenon, this study uses the MM5 regional climate model in which the model is forced with a warm pole SST anomaly south of Madagascar.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1988.
Includes bibliographical references (leaves 178-180).
Analysis of vertical profiles of absolute horizontal velocity collected in January 1981, February 1982 and April 1982 in the central equatorial Pacific as part of the Pacific Equatorial Ocean Dynamics (PEQUOD) program, revealed two significant narrow band spectral peaks in the zonal velocity records, centered at vertical wavelengths of 560 and 350 stretched meters (sm). Both signals were present in all three cruises, but the 350 sm peak showed a more steady character in amplitude and a higher signal-to-noise ratio. In addition, its vertical scales corresponded to the scales of the conspicuous alternating flows generically called the equatorial deep jets in the past (the same terminology will be used here). Meridional velocity and vertical displacement spectra did not show any such energetic features. Energy in the 560 sm band roughly doubled between January 1981 and April 1982. Time lagged coherence results suggested upward phase propagation at time scales of about 4 years. East-west phase lines computed from zonally lagged coherences, tilted downward towards the west, implying westward phase propagation. Estimates of zonal wavelength (on the order of 10000 km) and period based on these coherence calculations, and the observed energy meridional structure at this vertical wavenumber band, seem consistent, within experimental errors, with the presence of a first meridional mode long Rossby wave packet, weakly modulated in the zonal direction. The equatorial deep jets, identified with the peak centered at 350 sm, are best defined as a finite narrow band process in vertical wavenumber (311-400 sm), accounting for only 20% of the total variance present in the broad band energetic background. At the jets wavenumber band, latitudinal energy scaling compared well with Kelvin wave theoretical values and a general tilt of phase lines downward towards the east yielded estimates of 10000-16000 km for the zonal wavelengths.
by Rui Vasques de Melo Ponte.
Ph.D.

The determination of the mechanisms setting the strength and structure of the large scale circulation is a fundamental and long-standing problem in physical oceanography. In this thesis, we seek to explore the mechanisms contributing to the steady state and variability of the large scale flow, with a focus on better understanding the dynamics of the Atlantic meridional overturning circulation (AMOC). In the first part of this thesis, we explore the linear sensitivity of the monthly mean subtropical AMOC to surface fluxes of buoyancy and momentum. Our approach is to use a numerical adjoint. Key insights are provided into the memory of the AMOC to historic atmospheric forcing. We find that significant memory to wind forcing is confined to timescales of less than a year. In contrast, we identify significant memory to surface buoyancy forcing spanning multi-decadal timescales and characterised by a large scale oscillation in the sign of sensitivity between the eastern and western North Atlantic basin. An important result is that to understand the origins of seasonal variability in the modelled AMOC, we must examine the response to a multidecadal history of atmospheric forcing. In the second part of this thesis, a new tool is presented that enables a clean diagnosis of the force balance controlling the circulation regime for a Boussinesq fluid. Specifically, the tool is based on the development of the "rotational momentum" equations and sets of scalar "velocity potentials" and analogous "force functions". The latter allow the projection of all forces onto the acceleration of the vertical shears and external modes of overturning to be visualised in isolation. The rotational momentum decomposition is applied to the modelled circulation in idealised Atlantic and global configurations of the MITgcm, with a focus on elucidating the dynamics of the simulated AMOC. We discuss the key role played by the rotational buoyancy forcing right on the western boundary.

Pteropods are holoplanktonic gastropod molluscs found globally. Although species diversity is greater at lower latitudes, species abundance is greater at temperate and polar latitudes. Declines in pteropod populations have not only been correlated to declines of their major predators, but pteropods have also been used as bioindicators of global environmental changes such as ocean acidification. With high latitude abundances, pteropods provide significant sustenance for species such as the Atlantic salmon in the Atlantic Ocean and Pleuragramma antarcticum in the Southern Ocean. Because pteropods eat phytoplankton and other pteropods, factors that affect pteropod abundance influence many trophic levels. This dissertation explores ecological, physiological and trophodynamic relationships of pteropods when considering the influences of environmental factors observed to be altering the western Antarctic Peninsula's marine ecosystem. Over the last few decades very few studies have reported the distributions of pteropods along the western Antarctic Peninsula, in particular south of the Gerlache Strait. The ecological study provided the first detailed report of the pteropods Spongiobranchaea australis and Clione antarctica along the western Antarctic Peninsula south of the Gerlache Strait, and their local distribution was correlated to the region's major water masses and mesoscale water mass circulation. The physiological study of S. australis and C. antarctica yielded the first account of their metabolism, ratios of oxygen consumed to nitrogen excreted, proximate body composition, primary substrates oxidized, and enzymatic activities along the study's latitudinal gradient; the first report of S. australis' physiology anywhere around Antarctica. The final chapter utilized a comprehensive Ecopath with Ecosim model of the western Antarctic Peninsula's marine ecosystem. The model was used to explore the trophodynamic significance of pteropods within their polar marine ecosystem as well as changes in whole ecosystem trophodynamics by employing various climate change scenarios expected to alter the Peninsula's marine ecosystem over the next 40 years. The sum of these studies provides a foundation for exploring pteropods as bioindicators of environmental change along the western Antarctic Peninsula, a region currently experiencing considerable climate anomalies.

Two problems in oceanic/atmospheric modelling are examined in this thesis. In the first problem the release of fresh water from a midlatitude estuary to the continental shelf is modelled numerically as a Rossby adjustment problem using a primitive equation model. As the initial salinity front is relaxed, a first baroclinic mode Kelvin wave propagates into the estuary, while along the continental shelf, the disturbance travels in the direction of coastally trapped waves but with a relatively slow propagation speed. When a submarine canyon extends offshore from the estuary, the joint effect of baroclinicity and bottom relief provides forcing for barotropic flow. The disturbance now propagates along the shelf at the first coastally trapped wave mode phase speed, and the shelf circulation is significantly more energetic and barotropic than in the case without the canyon. For both the experiments with and without a canyon an anticyclonic circulation is formed off the mouth of the estuary, generated by the surface outflow and deeper inflow over changing bottom topography. As the deeper inflow encounters shallower depth, the column of fluid is vertically compressed, thereby spinning up anticyclonically due to the conservation of potential vorticity. This feature is in qualitative agreement with the Tully eddy observed off Juan de Fuca Strait. A study of the reverse estuary (where the estuarine water is denser than the oceanic water) shows that this configuration has more potential energy available for conversion to kinetic energy than the normal estuary. Bass Strait may be considered as a possible reverse estuary source for the generation of coastally trapped waves. Model solutions are compared with field observations in the Bass Strait region and with the results of the Australian Coastal Experiment. The effects of a wider shelf and a wider estuary are examined by two more experiments. For the wider shelf, the resulting baroclinic flow is similar to that of the other runs, although the barotropic flow is weaker. The wide estuary model proves to be the most dynamic of all, with the intensified anticyclonic circulation now extending well into the estuary. In the second problem the effect of the horizontal structure of midlatitude oceanic heating on the stationary atmospheric response is examined by means of a continuously stratified model and a simple two level model, both in the quasigeostrophic β-plane approximation. Solutions are obtained for three non-periodic zonal heating structures (line source, segmented cosine, and segmented sine). Little difference is observed between the solutions for these two different models (continuously stratified and two level). There are two cases which emerge in obtaining analytic solutions. In case 1, for large meridional wavenumbers, there exists a large local response and a constant downstream response. In case 2, for small meridional wavenumbers, the far field response is now sinusoidal. A critical wavenumber separating these two cases is obtained. The effect of oceanic heating on the atmosphere over the Kuroshio region is examined in an attempt to explain the large correlations observed between winter Kuroshio oceanic heat flux anomalies, and the winter atmospheric surface pressure and 500 & 700 mb geopotential heights, both upstream and downstream of the heating region. In both models, the response is consistent with the observed correlations. When western North Pacific heating and eastern North Pacific cooling are introduced into the models, a large low pressure response is observed over the central North Pacific. This feature is in excellent agreement with the observed correlations. A time dependent, periodic, two level model (with and without surface friction) is also introduced in order to study the transient atmospheric response to oceanic heating. The height at which the thermodynamic equation is applied is found to be crucial in determining the response of this model. When the heating is entered into the model near to the surface, unstable modes are prevalent sooner than they would be when the heat forcing is applied at a higher level. As in the steady state models, two cases dependent on the meridional wavenumber ɭ emerge in the analysis. For small scale meridional heating structures (large ɭ), the response consists of an upper level high and a lower level low which propagate eastward with time. For large scale meridional heating structures (small ɭ) the response essentially consists of a wavenumber 3-4 perturbation superimposed on the solution for large ɭ.
Science, Faculty of
Mathematics, Department of
Graduate

An eddy-resolving upper ocean model is developed to study the dynamics and thermo-dynamics of Baie des Chaleurs (BdC, 47.5-48.5N, 65.5-66.5W), Gulf of St. Lawrence (GSL), Canada. The model has primitive equation dynamics with two active layers embedded with a Kraus-Niiler type mixed layer model at the top.
Forced by observed wind, atmospheric heat fluxes, river runoff and appropriate remote forcing (in particular, the Gaspe Current, GC), the model demonstrates that the mean cyclonic general circulation pattern in the bay is a consequence of the intrusion of the GC. In the mixed layer, atmospheric heat fluxes and horizontal thermal advection play a key role in the thermal balance at the eastern part of the bay. The local mixed layer fluctuations are controlled by wind and GC induced divergence. The entrainment (and its corresponding heat flux) is important at the western part of the bay and changes the mean mixed layer depth on a time scale of more than a week. Varying GC intensified the flow variations induced by the wind in the bay and improved simulation results as compared with observations.
Sensitivity runs are conducted to study the effects of external forcing, important physical processes and the internal physical parameterisation on the model results and to compare these with the main model run. Experiments show that nonlinearity is very important in determining the circulation pattern in the bay. Changing external thermal forcing also modifies dynamical processes in the BdC. The fluctuations in the near surface temperature are mainly due to latent and sensible heat changes. The parameter study indicates that, the model is not overly sensitive to changes in most of the parameters, but suggests that sensitivity of the mixed layer physical parameters depends on the dynamical and thermodynamic system applied.
Hydrographic and current meter data are used first to study the variability of both the dynamics and thermodynamics in the BdC and its relation to the separation/intrusion of the unsteady GC. A numerical model is then applied to gain insight into the problem. The time scales of interest range from tidal to seasonal.
The results show that the kinetic energy in the BdC is dominated by the semi-diurnal tide (M$ sb2$) and periods of 5-10 days for high and low frequency bands, respectively. Most of the energy in the low frequency band is found to be induced by wind-related forcing.
Both observations and model results indicate that seasonal variations in the BdC are strongly related to the characteristics of separation/intrusion of the GC, which is mainly controlled by its transport magnitude as well as phase, duration and strength of its acceleration (or deceleration). The separation occurs when (adverse) vorticity having an opposite sign from that existing upstream is generated near the separation area. Although the separation can be generated in a decelerating GC, it can also occur in an accelerating GC when the GC is strong enough to advect upstream vorticity necessary to form a recirculation and the related adverse vorticity downstream. Nonlinearity is critical to the separation. Nevertheless, separation can be generated in a linear current with strong deceleration. The GC intrudes either along the coastline (attachment) into the bay by a non-separated GC or following the separation of the GC (reattachment). Effects of various physical processes on the separation/intrusion and variability of eddies in the BdC are examined.

This thesis presents several ways to understand transports of air and water masses in the atmosphere and ocean, and the transports of energy that they imply. It presents work using various kinds of observations as well as computer simulations of the atmosphere and oceans. One of the main focuses is to identify similarities and differences between models and observations, as well as between different models. The first half of the thesis applies Lagrangian methods to study flows in the atmosphere and oceans. Part of the work focuses on understanding how particles follow the currents in the Baltic Sea and how they disperse. It is suggested that the commonly used regional ocean model for the Baltic Sea, RCO, underestimates the transport and the dispersion of the particles, which can have consequences for studies of e.g. biogeochemistry as well as for operational use. A similar methodology is used to study how particles are transported between the tropics and mid-latitudes by the large-scale atmospheric circulation. It is found that the mass transport associated with northbound and southbound particles can cancel in the zonally averaged circulation, and we propose that the degree of cancellation depends on the method of averaging. The latter half of the thesis focuses on Eulerian stream functions and specifically a thermodynamic stream function that combines the zonal and meridional circulations of the atmosphere into a single circulation. The results are used to study the inter-annual variability of the intensity and thermodynamic properties of the global atmospheric circulation. A significant correlation to ENSO variability is found both in reanalysis and the EC-Earth coupled climate model. It is also shown that a set of models from the CMIP5 project show a slowdown of the atmospheric circulation as a result of global warming and associated changes in near-surface moisture content and upper-level radiative cooling.
Denna avhandling presenterar olika metoder för att studera datormodeller av atmosfä- ren, haven, och klimatsystemet. Metoderna använder såväl Lagrangeska synsätt dvs att betrakta atmosfären eller haven som individuella partiklar i rörelse, som Eulerska synsätt där atmosfären och haven ses som gas eller vätska i rörelse. I artikel 1 sjö- sätts ett antal “surface drifters” i Östersjön som driver fritt med havsströmmarna och vars hastighet mäts av satelliter. Genom att modellera Lagrangeska partiklars rörelser i Östersjön och jämföra med dessa “surface drifters” kan det visas att datormodeller kan underskatta både medelhastigheten av partiklarna samt deras utbredning. I ar- tikel 2 simuleras luftmassornas rörelser mellan tropikerna och mellanbreddgraderna (∼ 45◦N/S). Ett medelvärde över all longituder tenderar att ignorera betydande mass- och energitransporter mellan tropikerna och mellanbredderna, och dessa kvantifieras i detalj i artikel 2. Artiklarna 3 och 4 presenterar en metod för att studera atmosfärens storskaliga rörelser utifrån ett termodynamiskt perspektiv där luftmassornas värme och fukt studeras. Det visas att variationer ytvattentemperatur vid ekvatorn i Stilla havet kan få atmosfären att, i ett globalt medelvärde, bli fuktigare och varmare samtidigt som masstransporter- na saktar ner. På samma sätt visas att en global uppvärmning till följd av ökade utsläpp av växthusgaser kan få atmosfären att bli varmare, fuktigare och att masstransporterna kan sakta ner.

At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 3: In press; Paper 4: Manuscript.

BalticWay

Large-scale bed features are often encountered in coastal waters, and include sandbanks and spoil heaps. The morphodynamic development of such features involves complicated nonlinear interactions between the flow hydrodynamics, sediment transport, and bed profile. Numerical modelling of the morphodynamic evolution and migration of large-scale bed features is necessary in order to understand their long-term behaviour in response to changing environmental conditions. This thesis describes detailed measurements of the morphodynamics of sand mounds in unidirectional and oscillatory (tidal) flows, undertaken at the U.K. Coastal Research Facility (UKCRF). High quality data were collected, including water velocities, water levels and overhead images. The parameters tested are: three types of mound shape (circular and elliptical in plan shape, and Gaussian, cosine and triangular in cross-section); underlying fixed or mobile bed conditions; and initial crest height (submerged, surface-touching and surface-piercing). Peak flow velocities are about 0.5 m/s, the sand median grain size is 0.454 mm, and transport occurring mostly as bedload. When analysing the data, the bed contours are determined by digitising the shoreline at different water levels. From these plots, the volume, height, and centroid position of the mound are calculated. A large-scale fit method, based on a Gaussian function has been used to separate small-scale ripples from the large-scale bed structure during the evolution of an isolated sand mound or spoil heap. The bed profile after the ripples are removed is comparable to typical predictions by shallow-flow numerical solvers. The UKCRF experiments investigated the morphodynamic response of a bed mound to hydrodynamic forcing: shape changes, migration rates, volume decay and sediment transport rates. The measured migration rate and decay of a submerged sand mound in the UKCRF are found to be in satisfactory agreement with results from various theoretical models, such as the analytical solution derived by De Vriend. Numerical predictions of mound evolution by a commercial code, PISCES, are also presented for a fully submerged sand mound; the bed evolution is reasonably similar to that observed in the UKCRF. The data provided as a result of the research reported in this thesis provide insight into the behaviour of sand mounds in steady and unsteady flows at laboratory scale, and should also be useful for benchmark (validation) purposes to numerical modellers of large-scale morphodynamics.

This PhD thesis investigates the transport and distribution of short-lived halogenated organic substances in the tropical tropopause layer (TTL) in the Pacific Ocean. Short-lived halocarbons are one of the major groups of the ozone depleting substances as they provide a source for the active halogens which decrease ozone in the atmosphere. The TTL serves as the primary gateway of tropospheric air to enter the stratosphere. The air which enters the stratosphere is distributed all over the globe. Thus, the research on which tropospheric air masses go into the TTL, its structure and composition and the transport within is crucial. This thesis uses the UK Meteorological Office Lagrangian particle dispersion model NAME to (i) support the flight planning activities and achieve the multi aircraft coordination in CAST, CONTRAST, ATTREX 2014 campaigns, and (ii) quantify the amount and distribution of short-lived halocarbons in the TTL, and explain differences in these vertical distributions and transport characteristics. The halocarbons of interest are methyl iodide (CH3I), bromoform (CHBr3) and dibromomethane (CH2Br2). A new NAME procedure was developed and operated successfully to provide routine simulations and near real-time products suitable for guiding the CAST, CONTRAST and ATTREX aircraft in order to achieve their mission scientific objectives, and to make coordinated measurements. NAME was used post-campaign to analyse distribution of short-lived halocarbons in the TTL, identify their source regions and transport timescales. A new approach is proposed to investigate the TTL composition in terms of the boundary layer air influence, and subsequently quantify CH3I, CHBr3 and CH2Br2 by estimating their boundary layer and background contribution. The sums of these modelled estimates are in good agreement with the ATTREX 2014 and 2013 CH3I, CHBr3 and CH2Br2 observations. The quantification of the contribution of short-lived bromocarbons to the active bromine in the TTL was achieved, and the results lie within the range of the recent literature studies. The final focus of this thesis is on how well NAME represents the particle displacement via convection. Convection is the major transport pathway for the short-lived halocarbons to reach the TTL. The role of convection in transporting CH3I, CHBr3 and CH2Br2 to the TTL is assessed using the new convection scheme in NAME. A validation of the performance of this scheme is provided, showing that it yields improved and more realistic representation of the particle displacement via convection.

The ocean emission and subsequent oxidation of dimethylsulfide (DMS) provides a source of sulfate in the atmosphere, potentially affecting the amount of solar radiation reaching the Earth's surface through both direct and indirect radiative effects of sulfate aerosols. DMS in the ocean can be quite variable with season and location, which in turn leads to high spatial and temporal variability of ocean DMS emissions. This study tested currently available observational and empirically-based climatologies of DMS concentration in the surface ocean. The exploration of the existing parameterizations mainly reveals the limitations of estimating DMS with an empirical model based on variables such as chlorophyll and mixed layer depth. The different algorithms show significant differences in spatial pattern, and none correlate strongly with observations. There is considerable uncertainty both in terms of the spatiotemporal distribution in DMS concentration and flux, as well as in the global total DMS flux. The present research investigates the influence of DMS on sulfate aerosols and radiative fluxes given different DMS climatologies in the fourth generation of the Canadian Global Atmospheric Climate Model (CanAM4.1). In general, the response in the radiative flux seems to follow the variation in the global mean flux of DMS linearly. Differences in the spatial and temporal structure of oceanic DMS have only a secondary effect on the radiative changes. The overall response of the atmosphere to the presence or absence of structure of DMS in space and time is distinctly smaller compared to the possible uncertainty of this response associated with the magnitude of the annually averaged global flux.
Graduate
0425
0725
0416
jetesdal@uvic.ca

Today, ocean modeling is fast developing as a versatile tool for the study of earth’s climate, local marine ecosystems and coastal engineering applications. Though the field of ocean modeling began in the early 1950s along with the development of climate models and primitive computers, even today, the state-of-the-art ocean models have their own limitations. Many issues still remain such as the uncertainity in the parameterisation of essential processes that occur on spatial and temporal scales smaller than that can be resolved in model calculations, atmospheric forcing of the ocean and the boundary and initial conditions. The advent of data assimilation into ocean modeling has heralded a new era in the field of ocean modeling and oceanic sciences. “Data assimilation” is a methodology in which observations are used to improve the forecasting skill of operational meteorological models. The study in the present thesis mainly focuses on obtaining a four dimensional realization (the spatial description coupled with the time evolution) of the oceanic flow that is simultaneously consistent with the observational evidence and with the dynamical equations of motion and to provide initial conditions for predictions of oceanic circulation and tracer distribution. A good implementation of data assimilation can be achieved with the availability of large number of good quality observations of the oceanic fields as both synoptic and in-situ data. With the technology in satellite oceanography and insitu measurements advancing by leaps over the past two decades, good synoptic and insitu observations of oceanic fields have been achieved. The current and expected explosion in remotely sensed and insitu measured oceanographic data is ushering a new age of ocean modeling and data assimilation. The thesis presents results of analysis of the impact of data assimilation in an ocean general circulation model of the North Indian Ocean. In this thesis we have studied the impact of assimilation of temperature and salinity profiles from Argo floats and Sea Surface height anomalies from satellite altimeters in a Sigma-coordinate Indian Ocean model. An ocean data assimilation system based on the Regional Ocean Modeling System (ROMS) for the Indian Ocean is used. This model is implemented, validated and applied in a climatological simulation experiment to study the circulation in the Indian Ocean. The validated model is then used for the implementation of the data assimilation system for the Indian Ocean region. This dissertation presents the qualitative and quantitative comparisons of the model simulations with and without subsurface temperature and salinity profiles and sea surface height anamoly data assimilation for the Indian Ocean region. This is the first ever reported data assimilation studies of the Argo subsurface temperature and salinity profile data with ROMS in the Indian Ocean region.

Long-duration records are necessary to understand and assess the long-term dynamics of natural systems. The purpose of this research was to use dendrochronologic modelling to construct proxy histories of hydroclimatic conditions and Pacific salmon abundance in west central British Columbia. A multi-species regional network of tree ring-width and ring-density measurements was established from new and archived tree-ring chronologies. These chronologies were then used in multivariate linear regression models to construct proxy records of nival river discharge, summer temperature, end-of-winter snow-water equivalent (SWE), the winter Pacific North America pattern (PNA) and Pacific salmon abundance. All proxy hydroclimate records provide information back to 1660 AD. Reconstructions of July-August mean runoff for the Skeena and Atnarko rivers describe below average conditions during the early- to mid-1700s and parts of the early-, mid- and late-1900s. Models describe intervals of above average river discharge during the late-1600s, the early-1700s and 1800s, and parts of the early- and mid-1900s. Fluctuations in proxy reconstructions of July-August mean temperature for Wistaria and Tatlayoko Lake, May 1 SWE at Mount Cronin and Tatlayoko Lake and October-February PNA occurred in near synchrony with the shifts described in runoff records. Episodes of above average runoff were typically associated with periods of enhanced end-of-winter SWE, below average summer temperature and positive winter PNA. A history of Pacific salmon abundance was reconstructed for four species of salmon (chinook, sockeye, chum and pink) that migrate to coastal watersheds of west central British Columbia. Proxy records vary in length and extend from 1400 AD, 1536 AD and 1638 AD to present. Salmon abundance reconstructions varied throughout the past six centuries and described significant collapse in population levels during the early-1400s, the late-1500s, the mid-1600s, the early-1700s, the early-1800s and parts of the 1900s. Wavelet analyses of reconstructed hydroclimate and salmon population records revealed low- and high-frequency cycles in the data. Correlation analyses related reconstructions to atmospheric teleconnection indices describing variability in North Pacific sea surface temperatures and the Aleutian Low pressure centre. To a lesser degree, relationships were also established between reconstructions and the El Niño-Southern Oscillation. Results thus confirm the long-term influence of large-scale ocean and atmospheric circulation patterns on hydroclimate and Pacific salmon abundance in west central British Columbia. The reconstructions introduced in this thesis provide insights about the long-term dynamics of the west central British Columbia environment. Several reconstructions presented in this thesis provide novel contributions to dendrohydroclimatic and paleoecologic research in Pacific North America. Proxy runoff records for the Skeena and Atnarko rivers are the first to be constructed for nival-regime basins in British Columbia. The models of Skeena River runoff and Mount Cronin SWE are additionally the first reconstructions of runoff and snowpack in Pacific North America based on a ring-density chronology, demonstrating the significant contribution that wood density measurements can make to dendrohydroclimate research. The models of Pacific salmon stocks are the first to utilize climate-sensitive tree-ring records to construct a history of regional salmon abundance and thus represent a significant advancement to paleoecological modelling.
Graduate