Abstract The research was conducted as a part of the phase III of the KEEP(Kuroshio Edge Exchange Processes)program. Two strings of sediment traps were deployed simultaneously: one near the outlet of North Mien-Hua Canyon (T15), and the other at the south rim of the South Okinawa Trough (T16). The purposes are to collect settling particulates at various depths for the studies of temporal and spatial variations of the particulate flux, 210Pb activity, 210Pb flux and size distribution. The particulate fluxes showed synchronous variations among the traps deployed at different depths of the same site. In general, the particulate flux in the marginal sea areas increases with depth but the maximum values may be at the mid-depth rather than at the deepest trap and remain so for the entire mooring period as observed at T15 and T16. Unusually high particulate fluxes could occur within the same period, probably reflecting an episodic event, such as typhoon or rain storm. 210Pb activity measured from different depths at T15 and T16 increases generally with depth along with the increase of the particulate flux toward the bottom. The temporal variation of 210Pb activity is generally smaller than that of the particulate flux in terms of relative amplitude. At the outlet of the canyon, T15, the temporal mean particulate flux of each trap ranged from 0.16 to 3.3 g/m2/d(a factor of ~ 20), while the mean 210Pb activity of each trap varied from about 98 to 168 dpm/g. At T16 located at the south rim of the South Okinawa Trough, the temporal mean particulate flux ranged from 0.06 to 5.7 g/m2/d(a factor of ~ 100), while the mean 210Pb activity varied from 82 to 192 dpm/g. The particulate 210Pb flux was smaller at T15 than at T16 because T15 has smaller particulate flux. The trapped particulates in the canyon(T1-T3) are mostly silt and sand, while the particulates collected from the Okinawa Trough(T15, T16) are mainly silt and clay. The 210Pb activity of the former is much lower than that of the latter, indicating the enrichment of 210Pb on the fine particulates. As the fine-grained particulates away from landmass have longer residence time in the ambient water, they can scavenge 210Pb more effectively.

In this study, the settling particulates collected by time-series sediment traps, sediment cores, and seawater samples taken in the western South Okinawa Trough were analyzed for 210Pb and 210Po in order to understand the characteristics of the particulates and sediments based on the distribution of these two nuclides and the extent of their radioactive disequilibrium. Two sediment traps were deployed at T18 (24¢X45'N 122¢X18'E, about 300m and 100m above bottom) from February to August 1999. The results show that higher mass fluxes were observed from February to April, ranging between 16 and 56 g/m2/d. The 210Pb activity increases systematically with time from about 80 to 100 dpm/g, and the upper trap has slightly higher values. Similar to 210Pb, the 210Po activity also increases, but from near zero to only 27 dpm/g for both traps, much lower than the corresponding 210Pb activity. The 210Pb activities are quite different between the settling particulates collected by traps at T18 and the surface sediment taken nearby (the former have a mean activity of about 85 to 90 dpm/g; the latter has a value of only 11 dpm/g). The size distribution and elemental composition are also different between the trapped particulates and the sediment. Thus the underlying sediments were not directly derived from the overlying trapped particulates. Except for T4 core below 15cm and T19 entire core, the 210Po/210Pb activity ratio in the sediments varies greatly, from near zero to 0.7, indicating deficiency of 210Po. Both 210Po and 210Pb activities are much lower in the sediments than in the settling particulates. A T19 both 210Po and 210Pb activities in the core decrease steeply from 120 dpm/g at surface to 60 dpm/g at 4 cm, indicating radioactive equilibrium. This is entirely different from the cores taken at other stations. The total 210Po/210Pb activity ratio in the water column at T17 is nearly constant at about 0.6, but drops to 0.3 below 700m, i.e. 210Po activity is deficient in the entire water column. At T18, the activity ratio is about 1.3 between 100m and 300m, indicating a 210Po excess in this layer. Below 400m, the ratio is about 0.6 to 0.7, showing 210Po deficit again. These observations indicate that the water columns at T17 and T18 are stratified, probably due to lateral transport. Based on the 210Po/210Pb activity ratio the mean residence time of 210Po with respect to particulate scavenging ranges from 3 to 16 months.

Water is essential to life on Earth. Since water exists in all three phases (solid, liquid, and gas) on Earth, it exists in various reservoirs throughout the planet that compose the hydrologic cycle, and its movement through these reservoirs requires energy. Thus, water is a key component of the energy balance of the Earth. Despite its importance, its representation in modeling and dataset generation is problematic. Here, the depiction of three phenomena, ocean surface turbulent fluxes, humidity inversions, and groundwater, are assessed, and suggestions for improvements of their representations are made. First, ocean surface turbulent fluxes, including those of moisture (latent heat flux), heat (sensible heat flux), and momentum (wind stress), from reanalysis, satellite-derived, and combined products which are commonly used to produce climatologies and to evaluate global climate models are compared to in situ observations from ship cruises to ascertain which products are the least problematic. The National Aeronautics and Space Administration’s reanalysis, the Modern Era Retrospective Analysis for Research and Applications, is the least problematic for all three fluxes, while a couple of others are the least problematic for only one of the three fluxes. Also, the product biases are disaggregated into uncertainties from the grid cell mean quantities, or bulk variables, used plus the residual uncertainties which includes the algorithm uncertainties due to the parameterization used to relate the small-scale turbulent processes to the large-scale bulk variables. The latter contribute the most to the majority of product latent heat fluxes, while both uncertainties can contribute the most to product sensible heat fluxes and wind stress. Thus, both algorithms and bulk variables need to be improved in ocean surface flux datasets. Second, humidity inversion climatologies in five reanalyses are evaluated. Humidity inversions, similar to its thermal counterpart, are layers in which specific humidity increases with height rather than the usual decrease with height. These are especially persistent in the polar regions in autumn and winter. However, Arctic inversions are the strongest in summer corresponding to the time of year that low cloud cover is the highest. Comparing the reanalysis inversions to radiosonde observations reveals some problems with the realization of humidity inversions in reanalyses including the misrepresentation of the diurnal cycle and of the overproduction of inversions in areas outside the polar regions. Finally, the simulation of groundwater in the Community Land Model (CLM) as used in the Community Earth System Model is made more realistic by including variable soil thickness. Because the bottom of the model soil column is placed at effectively bedrock, the unconfined aquifer model currently used in CLM is removed and a zero bottom water flux is put in place. The removal of the unconfined aquifer allows the simulation of groundwater to not be treated separately from soil moisture. The model is most affected where the number of soil layers is reduced from the original constant 10 layers and largely unaffected where the number of soil layers is increased except for baseflow where the mean annual range in rainfall is large.

The focus in this thesis is to improve knowledge of the BWR related uncertainties void, channel bow, and control rods. The presence of void determines the moderation of neutrons in BWRs. A high void fraction is less efficient in moderating neutrons than a low one. As a consequence, the ratio of thermal to fast neutrons is dependent on the surrounding void fraction. In this thesis, calculations with 2D/3D codes corroborate this dependence, the void correlation, to be linear and very robust to changes in different reactor parameters. The void fraction could be predicted from the ratio of simultaneously measured reaction rates from thermal and fast neutron detectors over the whole core with an uncertainty of ±1.5%. The only parameter found disturbing the void correlation significantly is channel bow. However, since channel bow is the only phenomenon found biasing the void correlation, it is found that the void prediction methodology can be used to indicate channel bow with a sensitivity of 4% per mm bow. Consequently, large channel bows could easily be detected. Increased knowledge of void fractions and channel bow could increase both safety and economy of nuclear power production. This thesis also investigates how 2D/3D codes used in production perform in calculating detailed impact of control rods on pin powers and their ability to perform control rod depletion calculations in the reflector region. It is found that the axial resolution used in 3D nodal codes has very large impact on pin power gradients, i.e., using a standard nodal size of ~15 cm can cause underestimations of 50% in pin power gradients, which could lead to fuel damages. In addition, two methods for determining the neutron flux in the control rod when it is withdrawn from the core are presented. Both methods can be used in a 3D nodal code to reproduce the neutron flux in the reflector region with an uncertainty of ±3%. / Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 715

Studies of trace gas fluxes have advanced the understanding of bulk interactions between the atmosphere and ecosystems. Micrometeorological instrumentation is currently unable to resolve vertical scalar sources and sinks within plant canopies. Inverted analytical Lagrangian equations provide a non-intrusive method to calculate source distributions. These equations are based on Taylor's (1921) description of scalar dispersion, which requires a measure of the degree of correlation between turbulent motions, defined by the Lagrangian length scale (L). Inverse Lagrangian (IL) analyses can be unstable, and the uncertainty in L leads to uncertainty in source predictions. A review of the literature on studies using IL analysis with various scalars in a multitude of canopy types found that parameterizations where L reduces to zero at the ground produce better results in the IL analysis than those that increase closer to the ground, but no individual L parameterization gives better results than any other does. The review also found that the relationship between L and the measurable Eulerian length scale (Le) may be more complex in plant canopies than the linear scaling investigated in boundary layer flows. The magnitude and profile shape of L was investigated within a corn and a forest canopy using field measurements to constrain an analytical Lagrangian equation. Measurements of net CO2 flux, soil-to-atmosphere CO2 flux, and in-canopy profiles of CO2 concentrations provided the information required to solve for L in a global optimization algorithm for half hour intervals. For dates when the corn was a strong CO2 sink, and for the majority of dates for the forest, the optimization frequently located L profiles that follow a convex shape. A constrained optimization then smoothed the profile shape to a sigmoidal equation. Inputting the optimized L profiles in the forward and inverse Lagrangian equations leads to strong correlations between measured and calculated concentrations (corn canopy: C_{calc} = 1.00C_{meas} +52.41 mumol m^{-3}, r^2 = 0.996; forest canopy: C_{calc} = 0.98C_{meas} +276.5 mumol m^{-3}, r^2 = 0.99) and fluxes (corn canopy: F_{soil} = 0.67F_{calc} - 0.12 mumol m^{-2}s^{-1}, r^2 = 0.71, F_{net} = 1.17F_{calc} + 1.97mumol m^{-2}s^{-1}, r^2 = 0.85; forest canopy: F_{soil} = 0.72F_{calc} - 1.92 mumol m^{-2}s^{-1}, r^2 = 0.18, F_{net} = 1.24F_{calc} + 0.65 mumol m^{-2}s^{-1}, r^2 = 0.88). In the corn canopy, coefficients of the sigmoidal equation were specific to each half hour and did not scale with any measured variable. Coefficients of the optimized L equation in the forest canopy scaled weakly with variables related to the stability above the canopy. Plausible L profiles for both canopies were associated with negative bulk Richardson number values. / Funding from NSERC.

Clear-sky top-of-atmosphere (TOA) fluxes are important in estimating the impact of clouds on our climate. In this study, we quantitatively compare the clear-sky fluxes measurements of the Clouds and the Earths Radiant Energy System (CERES) instrument to clear-sky fluxes from two reanalysis, NASA's Modern Era Retrospective-analysis for Research and Application (MERRA), and the European Center for Medium Range Weather Forecast Interim reanalysis (ERA-Interim). In the first comparison, we compare observed fluxes from individual cloud-free field-of- views to the reanalyses. In the second comparison, we compare monthly averaged observed clear-sky fluxes to those from the reanalyses. Monthly clear-sky fluxes are calculated by averaging fluxes from cloud-free regions. In both comparisons, the fluxes generally agree within +/- 10 W/m^2. Finally, we show that, while the differences between the fluxes of observations and the reanalyses are several W/m2, the inter-annual anomalies agree much better, with zonal and global average inter-annual anomalies typically agreeing within 1 W/m^2. The longwave clear-sky anomalies show excellent agreement even when comparing individual grid points, whereas the shortwave clear-sky anomalies are generally smaller at individual grid points.

This thesis investigates how benthic fluxes of phosphorus (P), nitrogen (N), and silicon (Si) change upon oxygenation of anoxic soft bottoms in the brackish, eutrophicated Baltic Sea. Direct measurements in situ by benthic landers demonstrated that fluxes of dissolved inorganic P (DIP) from anoxic bottom sediments in the Eastern Gotland Basin are higher than previously thought (Paper I). It is argued that the benthic DIP flux has a much larger influence on the DIP inventory in the Baltic proper than the external sources. Similarly, benthic fluxes of DIP and dissolved inorganic N (DIN) from anoxic sediment in the coastal Kanholmsfjärden Basin, Stockholm archipelago, were sufficiently high to renew the pools of these nutrients below the upper mixed layer in roughly one year (Paper II). A natural inflow of oxygen rich water into the deep, and previously long-term anoxic part of Kanholmsfjärden Basin, increased the P content in the sediment by 65% and lowered DIP and dissolved silica (DSi) concentrations in the pore water. These changes, as well as the large increases in benthic effluxes of these solutes following de-oxygenation of the bottom water, suggest that they are influenced similarly by changing oxygen conditions. Experimental results in papers III and IV show that common benthic macrofauna species in the Baltic Sea can stimulate benthic release of DIN and DSi, as well as dissolved organic and particulate bound nutrients. Thus, if benthic oxygen conditions would improve in the Baltic, initial effects on benthic–pelagic nutrient coupling will change due to animal colonisation of currently azoic soft bottoms. A new box corer was designed (Paper V) which can be used to obtain highly needed virtually undisturbed samples from soft bottom sediments – if lowered slowly and straight into the bottom strata – as demonstrated by in situ videography and turbidimetry. The commonly used USNEL box corer caused severe biasing during sediment collection. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript.</p> / Baltic oxygenation project

The impact of cold climate on physical and biological processes, especially the role of air and soil temperature in recovering photosynthesis and transpiration in boreal forests, was investigated in a series of studies. A process-based ecosystem model (CoupModel) considering atmospheric, soil and plant components was evaluated and developed using Generalized Likelihood Uncertainty Estimation (GLUE) and detailed measurements from three different sites. The model accurately described the variability in measurements within days, within years and between years. The forcing environmental conditions were shown to govern both aboveground and belowground processes and regulating carbon, water and heat fluxes. However, the various feedback mechanisms between vegetation and environmental conditions are still unclear, since simulations with one model assumption could not be rejected when compared with another. The strong interactions between soil temperature and moisture processes were indicated by the few behavioural models obtained when constrained by combined temperature and moisture criteria. Model performance on sensible and latent heat fluxes and net ecosystem exchange (NEE) also indicated the coupled processes within the system. Diurnal and seasonal courses of eddy flux data in boreal conifer ecosystems were reproduced successfully within defined ranges of parameter values. Air temperature was the major limiting factor for photosynthesis in early spring, autumn and winter, but soil temperature was a rather important limiting factor in late spring. Soil moisture and nitrogen showed indications of being more important for regulating photosynthesis in the summer period. The need for systematic monitoring of the entire system, covering both soil and plant components, was identified as a subject for future studies. The results from this modelling work could be applied to suggest improvements in management of forest and agriculture ecosystems in order to reduce greenhouse gas emissions and to find adaptations to future climate conditions. / QC 20110921 / the Nitro-Europe project

Κατά την διάρκεια του προγράμματος SESAME (Southern European Seas: Assessing and Modelling Ecosystem changes) χρηματοδοτούμενο από την ΕΕ, μετρήθηκαν σωματιδιακές ροές με την χρήση διάταξης ιζηματοπαγίδων στη Μαύρη Θάλασσα και ειδικότερα στη θέση 43ο01,950Ν, 29ο28,525Ε σε βάθος 2000m. Η διάταξη ποντίστηκε για 12 μήνες, σε δύο ποντίσεις, από 16 Οκτωβρίου 2007 έως 16 Οκτωβρίου 2008 και έφερε δύο ιζηματοπαγίδες σε βάθη 1000m και 1965m. Το καθιζάνον υλικό αναλύθηκε και μετρήθηκαν η ολική ροή, καθώς επίσης και οι ροές οργανικού C, ανθρακικών, βιογενούς Si και λιθογενούς κλάσματος. Οι χρονοσειρές των ροών έδειξαν έντονη διακύμανση σε όλη την διάρκεια του πειράματος και οι μέσες ετήσιες ολικές ροές ήταν 109 και 86 mg m-2 d-1, δείχνοντας μια μείωση με το βάθος. Το σωματιδιακό υλικό έδειξε μια εξαιρετική ομοιότητα ως προς την ποιοτική σύσταση στα δύο βάθη συλλογής και χαρακτηρίζεται από υψηλά ποσοστά οργανικού άνθρακα (10,5%). Γενικά το βιογενές υλικό, με περίπου 54%, κυριαρχεί του λιθογενούς που φτάνει το 46%. / As part of the SESAME (Southern European Seas: Assessing and Modelling Ecosystem changes) EU-funded research project, particle flux data was obtained with one instrumented array moored in SW Black Sea at 43ο01,950Ν, 29ο28,525Ε and 2000m depth. The mooring line was deployed over 12 months, from October 16th 2007 to October 16th 2008 and was equipped with two sediment trap-current meter pairs at 1000m and 1965m of water depth. The settling material was analyzed to obtain total mass, lithogenic, calcium carbonate, organic carbon and opal fluxes. Time-series of fluxes showed strong temporal variations over the experiment. The mean annual total mass fluxes were 109 and 86 mg m-2 d-1, showing a decrease with the depth. The qualitative composition of particulate matter was impressively similar at both depths of collection and it is characterized by high content of organic C, reaching 10,5%. Generally biogenic material dominates with around 54%, while lithogenic content was 46%.

Cette thèse concerne l'étude de l'interaction air-mer, due aux échanges de mouvements, avec un modèle idéalisé mais consistant. Les études sont réalisées à partir d'un modèle shallow-water bicouches (une pour l'océan et une pour l'atmosphère), avec une fine résolution spatiale et temporelle. L'interaction est uniquement due à la friction de surface entre les deux couches.Elle est implémentée par une loi de friction quadratique. La force appliquée à l'océan est calculée en utilisant la différence de vitesse entre les vents et les courants. Pour la force appliquée à l'atmosphère on distingue deux cas l'interaction ``1way'' et ``2way''. Pour la première, la friction appliquée à l'atmosphère néglige la dynamique de l'océan; elle est calculée en utilisant uniquement les vents. Pour l'interaction ``2W'', la friction appliquée à l'atmosphère est l'opposée de celle appliquée à l'océan.Trois configurations idéalisées sont explorées ici.La première configuration explique la génération d'une instabilité barotrope dans l'océan due à la force de friction quadratique et la dissipation visqueuse horizontale de l'atmosphère. Dans le cas 1W le cisaillement entraîne une instabilité barotrope dans l'océan. Dans le cas 2W, l'instabilité est amplifiée en amplitude et en dimension et est transférée à l'atmosphère. L'échelle principale de cette instabilité correspond à celle du rayon de Rossby dans l'océan. Elle est uniquement visible dans les modèles numériques, lorsque la dynamique est résolue à cette échelle à la fois dans l'océan mais aussi dans l'atmosphère.Dans la deuxième configuration, des expériences pour différentes valeurs du coefficient de traînée de surface sont réalisées. Le forçage diffère de la première configuration, et permet d'avoir une dynamique turbulente dans l'océan et l'atmosphère. L'énergie perdue par l'atmosphère et gagnée par l'océan par cisaillement à l'interface sont déterminées et comparées aux estimations basées sur les vitesses moyennes. La corrélations entre la vorticité océanique et atmosphérique est déterminée à l'échelle synoptique et méso-échelle de l'atmosphère. L'océan a un rôle passif, et absorbe l'énergie cinétique à quasiment tout les instants et tous les lieux. Les résultats différent des études réalisées à l'échelle du bassin. De par les faibles vitesses de l'océan, le transfert d'énergie dépend que faiblement des courants. La dynamique de l'océan laisse cependant son empreinte dans la dynamique de l'atmosphère conduisant à un état `quenched disorder' du système océan-atmosphère, pour le plus fort coefficient de friction utilisé.La dernière configuration, considère l'échange de mouvements entre l'océan et l'atmosphère autour d'une île circulaire. Dans les simulations actuelles de la dynamique océanique, le champs du forçage atmosphérique est généralement trop grossier pour inclure la présence de petites îles (<100km). Dans les calculs présentés ici, l'île est représenté dans la couche atmosphérique par un coefficient de traînée cent fois plus fort au dessus de l'île que l'océan. Cela engendre de la vorticité dans l'atmosphère , autour et près du sillage de l'île. L'influence de la vorticité atmosphérique sur la vorticité de l'océan, l'upwelling, la turbulence et le transfert d'énergieest considéré en utilisant des simulations couplées océan-atmosphère.Les résultats sont comparés avec des simulations ayant un forçage atmosphérique constant dans le temps et l'espace (pas de sillage) et des simulations "1W" (pour lesquelles les courants n'ont pas d'influence sur l'atmosphère).Les résultats des simulations sont en accords avec les travaux et les observations précédemment réalisés, et confirment que le sillage atmosphérique est le principal processus générant des tourbillons océanique dans le lit de l'île. Il est aussi montré que la vorticité est injectée directement par le rotationel du vent, mais aussi par la force du vent perpendiculaireau gradient d'épaisseur de la couche de surface océanique. / This thesis considers air-sea interaction, due to momentum exchange, in an idealized but consistent model. Two superposed one-layer fine-resolution shallow-water models are numerically integrated. The upper layer represents the atmosphere and the lower layer the ocean. The interaction is only due to the shear between the two layers. The shear applied to the ocean is calculated using the velocity difference between the ocean and the atmosphere.The frictional force between the two-layers is implemented using the quadratic drag law. Three idealized configurations are explored.First, a new mechanism that induces barotropic instability in the ocean is discussed. It is due to air-sea interaction with a quadratic drag law and horizontal viscous dissipation in the atmosphere. I show that the instability spreads to the atmosphere. The preferred spatial scale of the instability is that of the oceanic baroclinic Rossby radius of deformation.It can only be represented in numerical models, when the dynamics at this scale is resolved in the atmosphere and the ocean.In one-way interaction the shear applied to the atmosphere neglectsthe ocean dynamics, it is calculated using the atmospheric wind, only. In two-way interaction it is opposite to the shear applied to the ocean.In the one-way interaction the atmospheric shear leads to a barotropic instability in the ocean. The instability in the ocean is amplified, in amplitude and scale, in two-way interaction and also triggers an instability in the atmosphere.Second, the air-sea interaction at the atmospheric synoptic and mesoscale due to momentum transfer, only, is considered. Experiments with different values of the surface friction drag coefficient are performed, with a different atmospheric forcing from the first configuration, that leads to a turbulent dynamics in the atmosphere and the ocean. The actual energy loss of the atmosphere and the energy gain by the ocean, due to the inter-facial shear,is determined and compared to the estimates based on average speeds.The correlation between the vorticity in the atmosphere and the ocean is determined. Results differ from previous investigations where the exchange of momentum was considered at basin scale. It is shown that the ocean has a passive role, absorbing kinetic energy at nearly all times and locations.Due to the feeble velocities in the ocean, the energy transfer depends only weakly on the ocean velocity. The ocean dynamics leaves nevertheless its imprint in the atmospheric dynamics leading to a quenched disordered state of the atmosphere-ocean system, for the highest value of the friction coefficient considered. This finding questions the ergodic hypothesis, which is at the basis of a large number of experimental, observational and numericalresults in ocean, atmosphere and climate dynamics.The last configuration considers the air-sea interaction, due to momentum exchange, around a circular island. In todays simulations of the ocean dynamics, the atmospheric forcing fields are usually too coarse to include the presence of smaller islands (typically $<$ 100km).In the calculations presented here, the island is represented in the atmospheric layer by a hundred fold increased drag coefficient above the island as compared to the ocean. It leads to an increased atmospheric vorticity in the vicinity and in the wake of the island. The influence of the atmospheric vorticity on the ocean vorticity, upwelling, turbulence and energy transfer is considered by performing fully coupled simulations of the atmosphere-oceandynamics. The results are compared to simulations with a constant, in space and time, atmospheric forcing (no wake) and simulations with one-waycoupling only (where the ocean velocity has no influence on the atmosphere).Results of our simulations agree with previous published work and observations, and confirm that the wind-wake is the main process leading to mesoscale oceanic eddies in the lee of an island.