Zonal Volume Research Articles

Subsurface eddies east of the Philippines: Geographic characteristics, vertical structures, volume and thermohaline transport

Energetic subsurface eddies (SSEs) play a significant role in regulating the subthermocline circulation east of the Philippines. However, due to the paucity of targeted observations, they remain largely unexplored. By analyzing the outputs from an eddy-resolving ocean general circulation model (OGCM), this study investigated the statistics of SSEs east of the Philippines, including their geographic characteristics, vertical structures, and eddy-induced transport. During the period of 2009–2019, approximately 1927 and 1176 SSEs were detected to be anticyclonic and cyclonic, respectively, indicating the predominance of subsurface anticyclonic eddies (SSAE). The hotspot area of SSEs is in the latitude band of 6° N–15° N off the Philippine coast, especially around 10° N and 14° N–15° N prevailing abundant SSEs. Most SSEs originate at ∼138° E furthest with a mean lifespan of 55 days and a westward translation speed of 6 cm/s. The composite SSAE exhibits a typical subsurface-intensified feature with a velocity core at ∼520 m, while the subsurface cyclonic eddy (SSCE) has a relatively shallow core at ∼420 m and exhibits considerable strength near the surface with a rotating speed is around 5 cm/s. Temperature anomalies induced by SSEs show a dual-core structure associated with lens-like isopycnal undulations, and salinity anomalies are characterized by an alternating positive and negative signal owing to the complexity of the water masses. SSEs-induced meridional volume transport mainly occurs off the Philippine coast, where the northward transport is approximately 0.3 Sv and the southward transport is approximately 0.5 Sv. The zonal volume transport of SSEs is 1–2 Sv per latitude and mainly occurs in the North Equatorial Current (NEC) region. SSEs-induced stirring heat/salt transport is 1–2 orders larger than the trapping component and is mainly concentrated near the Mindanao coast. The meridional stirring heat transport is equatorward, which is up to 2.7 × 107 W/m, and the salt transport is northward with a magnitude of ∼100 kg·m−1·s−1 between 200 m and 2000 m. At the 8°N section, the mean salt transport associated with SSEs is about 24% of that induced by the Mindanao Undercurrent (MUC).

Association of prostate zonal volume with location and aggressiveness of clinically significant prostate cancer: A multiparametric MRI study according to PI-RADS version 2.1

BackgroundThe relationship between prostate cancer (PCa) and benign prostatic hyperplasia (BPH) remains unclear. This study aimed to determine whether prostate zonal volume was associated with the location and aggressiveness of PCa. Methods412 PCa patients were retrospectively enrolled. The volumes of the whole prostate (V) and transition zone (Vtz) were calculated by the prolate ellipsoid formula, and volume of the peripheral zone (Vpz) was calculated by their subtraction. Locations of PCa were divided into three categories, including peripheral zone (PZ), transition zone (Vtz) and mixed zone group. The mixed zone group was further divided into PZ-dominated, TZ-dominated and equally distributed subgroups. ResultsThe Vtz of Gleason score (GS) 3 + 4 group was the largest, while the Vpz of GS 9 group was the largest. Tumor diameters of the PZ and TZ groups were weakly correlated with their corresponding zonal volume (r = 0.261, p < 0.001; r = 0.311, p = 0.009, respectively). There was no significant difference in the zonal volumes and GS distribution among the location groups. The proportion of tumors with high-grade GS of 8 and 9 was higher in the PZ than that in the TZ group (38.5 vs 24.3%, p = 0.041). For tumors located in the TZ, the V and Vpz of tumors with high-grade GS were larger than those in the low-grade GS of 7 group (p = 0.033 and 0.039, respectively). Among the subgroups of mixed zone group, the Vtz of the TZ-dominated group was larger than those of PZ-dominated and equally distributed groups (p = 0.016 and 0.001, respectively). ConclusionPCa with high-grade GS is more likely to have a relatively larger Vpz and involve PZ, while PCa with a larger Vtz is more likely to be with low-grade GS, which support the theoretical model that pressure exerted by increasing prostate size/mechanical deformation may inhibit PCa growth from the clinical point. However, the increase in zonal volume might not be the direct cause of tumorigenesis and aggressiveness.

Volume Preserving Simulation of Soft Tissue with Skin

Simulation of human soft tissues in contact with their environment is essential in many fields, including visual effects and apparel design. Biological tissues are nearly incompressible. However, standard methods employ compressible elasticity models and achieve incompressibility indirectly by setting Poisson's ratio to be close to 0.5. This approach can produce results that are plausible qualitatively but inaccurate quantatively. This approach also causes numerical instabilities and locking in coarse discretizations or otherwise poses a prohibitive restriction on the size of the time step. We propose a novel approach to alleviate these issues by replacing indirect volume preservation using Poisson's ratios with direct enforcement of zonal volume constraints, while controlling fine-scale volumetric deformation through a cell-wise compression penalty. To increase realism, we propose an epidermis model to mimic the dramatically higher surface stiffness on real skinned bodies. We demonstrate that our method produces stable realistic deformations with precise volume preservation but without locking artifacts. Due to the volume preservation not being tied to mesh discretization, our method also allows a resolution consistent simulation of incompressible materials. Our method improves the stability of the standard neo-Hookean model and the general compression recovery in the Stable neo-Hookean model.

Association Between Prostate Zonal Volume and Erectile Dysfunction in Patients With Benign Prostatic Hyperplasia.

IntroductionThe impact of prostate zonal volume on erectile function and penile Doppler parameters is not yet settled.AimTo assess the association between prostate zonal volume and erectile dysfunction in patients with benign prostatic hyperplasia.MethodsThis cross-sectional analytical study included 70 men (aged ≥ 40 years). Of them, 60 patients were assigned to 3 study groups (n = 20/each): group (A) patients who had lower urinary tract symptoms (LUTSs) and erectile dysfunction (ED), group (B) patients who had LUTSs with no ED, group (C) patients who had ED with no LUTS, and other 10 age-matched patients who had no LUTS or ED acted as a control group (D). All patients were subjected to detailed medical and sexual history. International prostate symptom score (IPSS) was used to assess LUTSs, and international index of erectile function (IIEF) was used to assess ED.Main Outcome MeasureTransrectal ultrasound and penile Doppler ultrasound were used to assess zonal anatomy of the prostate and the vascular pattern of erection.ResultsThere was a significant difference in IPSS between group A (26) and B (19) (P < .05). Each of groups A and C had significant lower peak systolic velocity (PSV) than each of groups B and D (P < .001/each). There was a significant positive correlation between transitional zone index (TZI) and IPSS (r = 0.71, P < .01), and significant negative correlation between TZI and both of IIEF (r = -0.48, P < .05) and PSV (r = -0.606, P < .05).ConclusionThis study clearly demonstrated that there were significant correlations between increased transitional zone volume, TZI, and decreased both of IIEF score and PSV.Qalawena MM, Al-Shatouri MA, Motawaa MA, et al. Association Between Prostate Zonal Volume and Erectile Dysfunction in Patients With Benign Prostatic Hyperplasia. Sex Med 2020;8:205–213.

Topographic Control of Southern Ocean Gyres and the Antarctic Circumpolar Current: A Barotropic Perspective

AbstractIn the Southern Ocean the Antarctic Circumpolar Current is significantly steered by large topographic features, and subpolar gyres form in their lee. The geometry of topographic features in the Southern Ocean is highly variable, but the influence of this variation on the large-scale flow is poorly understood. Using idealized barotropic simulations of a zonal channel with a meridional ridge, it is found that the ridge geometry is important for determining the net zonal volume transport. A relationship is observed between ridge width and volume transport that is determined by the form stress generated by the ridge. Gyre formation is also highly reliant on the ridge geometry. A steep ridge allows gyres to form within regions of unblocked geostrophic (f/H) contours, with an increase in gyre strength as the ridge width is reduced. These relationships among ridge width, gyre strength, and net zonal volume transport emerge to simultaneously satisfy the conservation of momentum and vorticity.

MP20-08 MR IMAGING OF PROSTATE CANCER SHOWS REDUCED ENHANCEMENT KINETIC CURVES IN MEN ON 5-ALPHA REDUCTASE INHIBITORS WITH IMPLICATIONS FOR CANCER DETECTION

You have accessJournal of UrologyImaging/Radiology: Uroradiology II1 Apr 2018MP20-08 MR IMAGING OF PROSTATE CANCER SHOWS REDUCED ENHANCEMENT KINETIC CURVES IN MEN ON 5-ALPHA REDUCTASE INHIBITORS WITH IMPLICATIONS FOR CANCER DETECTION Shivashankar Damodaran, Lori Mankowski Gettle, Kelcz Frederick, Glenn O Allen, kyle Richards, E. Jason Abel, Tracy Downs, and David Jarrard Shivashankar DamodaranShivashankar Damodaran More articles by this author , Lori Mankowski GettleLori Mankowski Gettle More articles by this author , Kelcz FrederickKelcz Frederick More articles by this author , Glenn O AllenGlenn O Allen More articles by this author , kyle Richardskyle Richards More articles by this author , E. Jason AbelE. Jason Abel More articles by this author , Tracy DownsTracy Downs More articles by this author , and David JarrardDavid Jarrard More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2018.02.678AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES 5-Alpha Reductase Inhibitors (5ARI) produce duration-dependent changes in blood flow, total volume (TV) and zonal volume (ZV) of the prostate. To date, the effect of 5ARI on prostate cancer (PC) detection with MRI has not been examined. The goal of the study was to determine if 5ARI increases the conspicuity of PC on MRI, especially in the background of benign prostatic hypertrophy METHODS IRB approved retrospective study of 682 men who underwent prostate MRI. There were 217 biopsy proven cancer cases of which 13 (6%) on 5ARI were matched to 25 (12%) not on ARI based on age and Gleason Score. Two experienced GU radiologists blinded to 5ARI use reviewed the MRIs and recorded Apparent Diffusion Coefficient (ADC), maximum enhancement over baseline, and enhancement curve types of the PC and BPH nodules were measured for each patient. Statistical analysis was performed using MedCalc. RESULTS PSA (9 (4.7 -22) vs 5.6 (4.9 - 8.1); 0.09) and prostate volume (76 (47.2- 98) vs. 56 (46.7- 62.8); p=0.07) trended higher in the 5ARI groups. There were less aggressive enhancement curves in both cancer lesions (p=0.06) and benign nodules (p=0.01) in patients on 5ARI (see Table). 5ARI had no effect on ADC or maximum enhancement above baseline for either cancer or BPH nodules. ADC values did not significantly differ in malignant (p= 0.1) and benign (p=0.7) nodules in patients on 5ARI. No increased enhancement over baseline in both cancer and BPH nodules (p=0.9 and p=0.6, respectively) was noted CONCLUSIONS When patients were on 5ARI for at least three months, there was a differential blunting of enhancement kinetic curves, which was significant for BPH nodules and less marked for cancer nodules. This differential alteration of enhancement kinetic curves of BPH nodules compared to cancer nodules might be utilized enhance prostate cancer nodule detection with MRI by administering short course of 5ARI before imaging. © 2018FiguresReferencesRelatedDetails Volume 199Issue 4SApril 2018Page: e255 Advertisement Copyright & Permissions© 2018MetricsAuthor Information Shivashankar Damodaran More articles by this author Lori Mankowski Gettle More articles by this author Kelcz Frederick More articles by this author Glenn O Allen More articles by this author kyle Richards More articles by this author E. Jason Abel More articles by this author Tracy Downs More articles by this author David Jarrard More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Basin-scale features of global sea level trends revealed by altimeter data from 1993 to 2013

In this study, altimeter sea level data (from http://www.aviso.oceanobs.com) are used to study large scale, non-uniform patterns of sea level trends of the world's major oceans from 1993 to 2013. The three major oceans: the Pacific Ocean, the Indian Ocean and the Atlantic Ocean, are all rising, with different large-scale patterns. The Indian Ocean has the greatest mean sea level rise trend at 4.06 mm/year. Standard deviations of the spatial distribution of Pacific Ocean and Indian Ocean sea levels have been increasing during the last two decades while those of the Atlantic Ocean have been decreasing. By defining a new index, the volume centroid of the upper ocean layers, we find that, during the past two decades, the meridional volume centroids of the three major oceans have been moving southward. The zonal volume centroids of the Pacific Ocean and the Indian Ocean are closely related, exhibiting almost opposite phases during the last two decades. The long-term trends of the zonal volume centroids of the Pacific and Indian Oceans reveal that the areas around the western Pacific warm pool are at great risk of extreme sea level rise.

The role of ocean gateways in the dynamics and sensitivity to wind stress of the early Antarctic Circumpolar Current

AbstractThe date of inception of the Antarctic Circumpolar Current is debated due to uncertainty in the relative opening times of Drake Passage and the Tasman Seaway. Using an idealized eddy‐resolving numerical ocean model, we investigate whether both ocean gateways have to be open to allow for a substantial circumpolar current. We find that overlapping continental barriers do not impede a circumpolar transport in excess of 50Sv, as long as a circumpolar path can be traced around the barriers. However, the presence of overlapping barriers does lead to an increased sensitivity of the current's volume transport to changes in wind stress. This change in sensitivity is interpreted in terms of the role of pressure drops across continental barriers and submerged bathymetry in balancing the momentum input by the surface wind stress. Specifically, when the pressure drop across continents is the main balancing sink of momentum, the zonal volume transport is sensitive to changes in wind stress. Changes in zonal volume transport take place via altering the depth‐independent part of the circumpolar transport rather than that arising from thermal wind shear. In such a scenario, isopycnals continue to slope steeply across the model Southern Ocean, implying a strong connection between the deep and surface oceans. This may have consequences for the meridional overturning circulation and its sensitivity to wind stress.

The Injection of Zonal Momentum by Buoyancy Forcing in a Southern Ocean Model

AbstractAn overturning circulation, driven by prescribed buoyancy forcing, is used to set a zonal volume transport in a reentrant channel ocean model with three isopycnal layers. The channel is designed to represent the Southern Ocean such that the forced overturning resembles the lower limb of the meridional overturning circulation (MOC). The relative contributions of wind and buoyancy forcing to the zonal circulation are examined. It is found that the zonal volume transport is strongly dependent on the buoyancy forcing and that the eddy kinetic energy is primarily set by wind stress forcing. The zonal momentum budget integrated over each layer is considered in the buoyancy-forced, wind-forced, and combined forcing case. At equilibrium, sources and sinks of momentum are balanced, but the transient spinup reveals the source of momentum for the current. In the buoyancy-forced case, the forcing creates a baroclinic shear with westward flow in the lower layer, allowing topographic form stress and bottom friction to act as the initial sources of eastward momentum, with bottom friction acting over a longer time frame. In the wind-forced and combined forcing cases, the surface wind stress dominates the initial momentum budget, and the time to reach equilibration is shorter in the combined forcing simulation. These results imply that future changes in the rate of formation of Antarctic Bottom Water may alter the volume transport of the Antarctic Circumpolar Current.

Deep Signatures of Southern Tropical Indian Ocean Annual Rossby Waves*

Abstract The southern tropical Indian Ocean contains a striking forced annual Rossby wave studied previously using satellite altimeter sea surface height data, surface wind fields, expendable bathythermograph ocean temperature data, and models. Here, the deep reach of this wave and its velocity are analyzed using density–depth profiles and 1000-dbar horizontal drift data from Argo. Significant annual cycles in isopycnal vertical displacements and zonal velocity persist to the deepest pressures to which Argo data can be mapped reliably in the region, 1600–1900 dbar. Phase propagation of the annual cycle of the directly measured zonal velocities at 1000 dbar suggests a zonal wavelength of about 6000 km—about the length of the deep basin in which the wave is found—and a westward phase speed of ~0.2 m s−1. Apparent upward phase propagation in isopycnal vertical displacements suggests energy propagation downward into the abyss. This pattern is clearer when accounting for both the potential and kinetic energy of the wave. The largest zonal current associated with this wave has a middepth maximum that decays rapidly up through the pycnocline and less rapidly with increasing depth, suggesting a first-vertical-mode structure. The anomalous zonal volume transport of this annually reversing current is ~27 × 106 m3 s−1 across 80°E in mid-November. The peak zonal velocity of 0.06 m s−1 implies a maximum zonal excursion of about 600 km associated with the wave over an annual cycle.

Upper ocean state estimation in the Southern Ocean Gas Exchange Experiment region using the four-dimensional variational technique

[1] A prototypical ocean circulation model, and associated 4-D variational data assimilation system, is configured in support of the Southern Ocean Gas Exchange Experiment (Southern Ocean GasEx). The regional circulation model has 4 km horizontal resolution and 5 m vertical resolution in the upper ocean. In situ temperature and salinity observations and remotely sensed, gridded sea surface temperature and sea surface height observations are combined with the circulation model between 6 March and 4 April 2008. The benefits of customized data assimilation in support of a single oceanographic cruise are illustrated using Southern Ocean GasEx as a case study. The assimilated fields fit the observations within their respective uncertainties and fit 4–6 times better than the initial guess solution before assimilation. The fit of the assimilated fields is up to 100 times closer to observations than various global state estimate products using a cost function variance metric. The space-time variability in mixed layer depth is consistent with the Southern Ocean GasEx observations and shows a deepening through March 2008. This variability is correlated with sea level height anomalies, sea surface temperature, and air temperature, during the assimilation window. The mixed layer depth estimate between 21 March and 4 April 2008 at the location of the Southern Ocean GasEx deliberate tracer release is 41–54 ± 6 m. The average zonal volume flux estimate is 16 ± 1.9 Sv (1 Sv is 106 m3 s−1) for latitudes 50.7°S–51.8°S, longitude 38.5°W. The zonal volume flux approximately halves during 6–16 March; temporal changes in volume flux are associated with geostrophic circulation but not with the Ekman circulation.

Brazil-Malvinas Confluence upper ocean temperature anomalies induced by an ENSO wind forcing

The Brazil-Malvinas Confluence (BMC) region constitutes one of the most important ocean features in the South Atlantic Ocean basin. Understanding the BMC upper ocean temperature variability could represent one of the key factors to understanding its connection to local and global ocean circulation. Some important local and remote ocean processes are related to the annual and interannual variability of its thermal/salt front position. This paper investigates the upper ocean variability in the BMC region under the influence of an El Niño/Southern Oscillation-type wind stress field using an oceanic general circulation model (Modular Ocean Model version 4.0). The results revealed the occurrence of positive anomalies, with values ranging from 0.5ºC to 1.0ºC (centered at 40.5ºS and 55.0ºW), near the BMC region associated with upper ocean velocity anomalies during the peak of the ocean kinetic energy phase. This mechanism was a response of a volume transport balance between the Brazil Current (BC) and the Malvinas Current (MC), the latter being accelerated by the Antarctic Circumpolar Current (ACC). The occurrence of positive anomalies was always associated with an enhanced BC meridional surface volume transport, together with a decrease of the ACC zonal volume transport, vertically integrated across the Drake Passage, and a correspondent decrease in the upper layer MC volume transport. It was possible to see negative upper layer temperature anomaly predominance just before the peak ocean kinetic energy month and positive anomaly predominance immediately following this month. The occurrence of upper layer temperature anomalies in the BMC region was not restricted to just the peak ocean kinetic energy month since they occurred throughout the perturbed experiment integration time.

Interhemispheric influence of surface buoyancy conditions on a circumpolar current

This study shows that the surface buoyancy conditions in the Northern Hemisphere may influence the stratification and transport of the Antarctic Circumpolar Current (ACC). We use a course‐resolution ocean general circulation model (OGCM) in an idealized single‐basin configuration with a circumpolar channel. A decrease in the magnitude of the surface temperature meridional gradient in the Northern Hemisphere reduces production of the deep water, affecting the interhemispheric Meridional Overturning Circulation (MOC) and deepening the thermocline in both hemispheres. The induced change of stratification in the Southern Hemisphere circumpolar region increases the zonal volume transport of circumpolar current because of an increase in the local meridional density gradient and the associated thermal wind shear, which is the dominant baroclinic component of the total volume transport. The result is robust to variations in the background vertical mixing and the parameterization scheme for mesoscale eddies.

Technology Update: Real-Time Fluid Tracking Optimizes Treatment Design, Improves Strategy

Collecting complete wellbore-temperature profiles during the placement of stimulation and diversion fluids has opened a new window to understanding and modifying matrix-stimulation, fracturing, and conformance treatments. Rapidly collected temperature profiles can identify precisely where fluids are entering the formation, allowing real-time optimization of the treatment through on-the-fly modification of the planned program. Such knowledge is necessary to improve stimulation-fluid placement across the entire treatment interval. The Halliburton StimWatch service identifies stimulation-fluid placement on the basis of changes in fluid properties that introduce variations in temperature gradients as the fluid moves inside the wellbore. This type of analysis provides a detailed understanding of the quality of treatment as applied to the designated intervals through a quantitative assessment of downhole flow rates. Monitoring Benefits Historically, it has been difficult to evaluate the placement of stimulation fluids during a multizone treatment in real time. As a result, the zonal volume of injected fluid is based completely on geological-data interpretation; prejob fluid-placement simulators provide only a theoretical prediction of the injection profile. Unknown and unpredictable downhole events occur during stimulation treatments and can have significant impact on treatment results. To achieve successful stimulation treatments, it is important to obtain the following information throughout the job:Injection profile—which zones are being treated effectively and which zones are not being treated.Effectiveness of a diversion process.Status of squeezed zones.Location of natural fractures. Service Description The StimWatch service follows the treatment as it progresses downhole, monitoring distributed temperature profiles obtained by use of the fiber-optic OptoLog Distributed Temperature Sensing (DTS) system. As changes in wellbore temperature are caused by the injection process, this information is converted into downhole injection profiles for a qualitative indicator of fluid distribution across the pay interval. This is performed without the need for shut-in periods or extensive preconditioning of the wellbore. The DTS fiber-optic-cable assembly can be deployed in a permanent or retrievable configuration. The assembly can be strapped to the completion casing or production tubing as a permanent installation. For retrievable scenarios in horizontal wells, coiled tubing can be used to position the assembly across the perforated interval.

The Anatomic Distribution and Pathological Characteristics of Prostate Cancer: A Mapping Analysis

Purpose: We mapped the location of prostate cancer in Korean men, and investigated the volume and tumor distribution in relation to clinicopathological variables. Materials and Methods: The volume of cancer and the anatomic location of each tumor foci were determined from 186 radical prostatectomy specimens, which were digitized to fit into a prototype prostate model. Using the computer-based digital images, the zonal cancer volume and distributional frequency were analyzed with respect to the clinical and pathological parameters, which were demonstrated in gray scales. Results: The preoperative serum prostate-specific antigen (PSA) level ranged from 2.0 to 38.9ng/ml. The mean cancer volume of the 186 specimens was 4.5ml (median 1.9ml, range 0.01-37.7). The impalpable cancers were located more anteriorly and in the transition zone, and were also were smaller in volume (2.7ml vs. 5.5ml, p=0.004) than the palpable cancers. Cancers with seminal vesicle invasion were located more medially in the peripheral zone, and were larger in volume than organ-confined cancers or cancers with extracapsular extension (13.2ml vs. 3.0ml, p<0.001). For Gleason scores of 2-6, 7, and 8-10, the mean cancer volumes were 2.2, 3.7 and 8.2ml, respectively (p<0.001). High grade cancers were located more medially in the peripheral zone, especially when approaching the apex. Conclusions: T1c cancers are located more anteriorly and in the transition zone; therefore, inclusion of these areas for targeted biopsy may help to improve the detection of cancer in patients with elevated PSA levels and impalpable prostate cancer. A medial location of seminal vesicle invasive cancers may imply an ejaculatory ducts route of invasion rather than a direct extracapsular extension. (Korean J Urol 2006;47:578-585) ꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏ

Lagrangian circulation of Antarctic Intermediate Water in the subtropical South Atlantic

Abstract This study combines float data from different projects collected between 1991 and 2003 in the South Atlantic to describe the flow of Antarctic Intermediate Water (AAIW). Velocity space–time averages are calculated for various grid resolutions and with cells deformed to match the bathymetry, f/H or f/h (with H being the water depth and h being the thickness of the AAIW layer). When judged by the degree of alignment between respective isolines and the resulting average velocity fields, the best grid is based on a nominal cell size of 3° (latitude) by 4° (longitude) with cell shapes deformed according to f/h. Using this grid, objectively estimated mean currents (and their associated errors), as well as meridional and zonal volume transports are estimated. Results show an anticyclonic Subtropical Gyre centred near 36°S and spanning from 23±1°S to 46±1°S. The South Atlantic Current meanders from 33°S to 46°S and shows a mean speed of 9.6±7.8 cm s−1 (8.5±3.5 Sv; 1 Sv=1×106 m3 s−1). The northern branch of the Subtropical Gyre is located between 22°S and 32°S and flows westward with a mean speed of 4.7±3.3 cm s−1 (9.3±3.4 Sv). Evidence of a cyclonic Tropical Gyre divided in two sub-cells is visible on the stream function.

111 poster workshop Zonal X-ray volume imaging

111 poster workshop Zonal X-ray volume imaging

Impact of Atmospheric Intraseasonal Variability in the Indian Ocean: Low-Frequency Rectification in Equatorial Surface Current and Transport

An ocean general circulation model (OGCM) is used to investigate the low-frequency (period longer than 90 days) rectification of atmospheric intraseasonal variability (10–90-day periods) in zonal surface current and transport of the equatorial Indian Ocean. A hierarchy of OGCM solutions is found in an actual tropical Indian Ocean basin for the period of 1988–2001. To help to identify and isolate nonlinear processes, a linear continuously stratified model and a 4-layer intermediate ocean model are also used. Results from the OGCM solutions suggest that intraseasonal atmospheric forcing acts to weaken the equatorial seasonal surface currents. Amplitudes of the spring and autumn eastward surface jets, the Wyrtki jets (WJ), and the westward surface current during January–March are reduced by as much as 15–25 cm s−1 by intraseasonal atmospheric forcing, and strengths of the rectification exhibit a significant interannual variability. Important processes that cause the low-frequency rectification are asymmetric response of mixed layer depth to easterly and westerly winds, entrainment, and upwelling of momentum. During spring and autumn, the westerly (easterly) phase of an intraseasonal event enhances (weakens or even reverses) the seasonal westerly winds, increases (decreases) equatorial convergence and entrainment, and thus deepens (thins) the mixed layer. A net, westward current is generated over an event mean because easterly wind acts on a thinner surface mixed layer whereas westerly wind acts on a thicker one. In contrast, during January–March when the seasonal winds are equatorial easterlies, surface currents are westward and equatorial undercurrents (EUC) develop. The rectified surface currents are eastward, which reduces the westward surface flow. This eastward rectification results largely from the vertical advection and entrainment of the EUC. The seasonal-to-interannual variability of the rectified surface flow is determined primarily from the seasonal cycle and interannual variability of the background state. Seasonal-to-interannual variability of the intraseasonal wind forcing also contributes. The rectified low-frequency zonal volume (heat) transports integrated over the entire water column along the Indian Ocean equator are persistently eastward with an amplitude of 0– 15 × 106 m3 s−1 (0–1.2 pW). This is because westerly winds generate equatorial downwelling, advecting the surface eastward momentum downward and giving an eastward subsurface current. Easterly winds cause equatorial upwelling and produce an eastward pressure gradient force that drives an eastward subsurface current. This eastward subsurface current is advected upward by upwelling. The mean effect over an intraseasonal event at the equator is to increase the eastward transport in the water column. In the layers above the thermocline, the rectified zonal volume (heat) transports are in the same direction as the rectified surface currents. Results from this paper may have important implications for understanding climate variability because modification of WJ strength and transports can affect the SST and heat storage in the equatorial Indian Ocean warm pool.

Decreased birefringence of the superficial zone collagen network in the canine knee (stifle) articular cartilage after long distance running training, detected by quantitative polarised light microscopy.

To investigate the effects of a one year programme of running training (up to 40 km/day for 15 weeks) on the spatial orientation pattern of collagen and glycosaminoglycans in articular cartilage in different parts of the knee (stifle) and shoulder joints of young beagle dogs. Area specific measurements of the optical path difference (= retardation, gamma) and the cartilage zone thickness were performed using conventional procedures and a new computer based quantitative polarised light microscopy method. Transmission electron microscopy was used to determine the zonal volume density of collagen fibrils. The concentrations of collagen and hydroxypyridinium crosslinks were investigated biochemically. Running training decreased gamma by 24-34% (p < 0.05) in the superficial zone of the lateral femoral condyle articular cartilage and at the centre of the tibial condyles. Gamma of glycosaminoglycans decreased by 26% (p < 0.05) in the superficial zone of the lateral condyle of the femur, but at the same site the volume density of collagen fibrils was unchanged. Neither the collagen concentration nor the concentration of hydroxypyridinium crosslinks was altered as a result of running. In both control and runner dogs, the thickness and gamma values of the superficial zone were greater in the humerus and the femur than in the tibia. Endurance type running exercise in beagles caused a reduction in the superficial zone birefringence of the articular cartilage, which indicates either a disorganisation or a reorientation of the superficial zone collagen network. Articular cartilage showed marked variability of collagen network organisation over the different knee (stifle) joint articular surfaces.

Monthly period oscillations in the Pacific North Equatorial Countercurrent

Monthly period oscillations in temperature and velocity in the vicinity of the North Equatorial Countercurrent along 140°W are examined using moored time series data collected during 1988–1989. These oscillations, which presumably derive their energy from instability of the large‐scale shear of the zonal equatorial current system, are found to be energetic across a broad band of periods of about 15–50 days. Along 7°N, wavelike motions at these periods propagate westward with a phase speed of about 30–40 cm s−1 and a zonal wavelength of 750–1150 km. The oscillations are approximately in geostrophic balance with the thermal field, with the velocity vector rotating anticyclonically around westward propagating high sea level centers. Zonal volume transport variations associated with these waves between 5° and 9°N at 20–180 m depth have a standard deviation of about 4.1 Sv, with peak‐to‐peak changes in some instances approaching 20 Sv. Maximum temperature variance along 140°W occurs between 5° and 7°N at 100–150 m depth in a region of strong mean vertical and meridional temperature gradient associated with a thermocline sloping upward to the north. At the surface, maximum temperature variability occurs from 2° to 5°N in the vicinity of the strong sea surface temperature front north of the equator. Analysis of the upper ocean temperature balance at 7°N, 140°W reveals that meridional advection is important both in the surface layer and in the thermocline. Vertical advection, estimated using vertical velocity calculated from a simplified linear vorticity balance, is also important in the thermocline, where it contributes a variance comparable to that of meridional advection. Zonal advection is likely to be significant in the upper 80 m, below which it is probably of secondary importance compared to meridional and vertical advection. One consequence of advection in the temperature balance is that variance is shifted toward lower frequencies in temperature vis‐a‐vis velocity spectra. This “red shift” may account for the apparent difference between periods for instability waves inferred from near‐equatorial meridional velocity spectra, and slightly longer periods reported for oscillations of the sea surface temperature front north of the equator based on satellite imagery.