Application of a nested-grid ocean circulation model to a shallow coastal embayment: Verification against observations

A nested-grid ocean circulation modeling system is used to study the response of Lunenburg Bay in Nova Scotia, Canada, to local wind-forcing, tides, remotely generated waves, and buoyancy forcing in the summer and fall of 2003. Quantitative comparisons between observations and model results demonstrate that the modeling system reproduces reasonably well the observed sea level, temperature, salinity, and currents in the bay. Numerical results reveal that the spatial and temporal variability of temperature and salinity in the bay during the study period is mainly forced by the local wind stress and surface heat/freshwater fluxes, with some contribution from tidal circulation. In particular, the local heat balance on the monthly timescale is dominated by cooling due to vertical advection and warming due to horizontal advection and net surface heat flux, while high-frequency variations (timescales of 1–30 days) are mainly associated with vertical advection, i.e., wind-induced upwelling and downwelling. There is also a strong baroclinic throughflow over the deep water region outside Lunenburg Bay that is strongly influenced by wind-forcing. The vertically integrated momentum balance analysis indicates a modified geostrophic balance on the monthly timescale and longer, and is dominated by the pressure term and wind minus bottom stress in the high-frequency band

Finite-Amplitude Evolution of Instabilities Associated with the Coastal Upwelling Front

A primitive equation model is used to study the finite-amplitude evolution of instabilities associated with the coastal upwelling front. Simulations of increasing complexity are examined that represent idealizations of summer conditions off the Oregon coast, including cases with steady and with time-variable wind in a domain with alongshore-uniform bathymetry and with time-variable wind in a domain with realistic Oregon coast bathymetry. The numerical results indicate that the fastest-growing mode in this system has approximately an 8–10-km alongshore wavelength but that, once the disturbances grow to finite amplitude, the predominant alongfront scale increases rapidly because of nonlinear effects. Separation of the total kinetic energy into contributions from the alongshore average flow and perturbation about that average shows that the initial growth of the perturbation kinetic energy is due to potential energy conversion, but transfer of energy from the kinetic energy of the alongshore average flow becomes important once the disturbances reach large amplitude. The time-variable wind simulations again show initial growth of small-scale instabilities followed by evolution to larger scales. In this case, however, even after larger-scale disturbances have developed on the upwelling front, smaller-scale patterns amplify along the front in response to each upwelling-favorable wind event. Realistic coastal bathymetry introduces additional alongshore topographic scales into the problem, but the formation of instabilities on small scales and evolution to larger scales are still ubiquitous. Where instabilities encounter strong curvature in the upwelling front produced by bathymetric effects, the upwelling front becomes highly contorted and horizontal variability is significantly enhanced

Global burden of disease of HIV-associated cryptococcal meningitis: an updated analysis.

BACKGROUND: Cryptococcus is the most common cause of meningitis in adults living with HIV in sub-Saharan Africa. Global burden estimates are crucial to guide prevention strategies and to determine treatment needs, and we aimed to provide an updated estimate of global incidence of HIV-associated cryptococcal disease. METHODS: We used 2014 Joint UN Programme on HIV and AIDS estimates of adults (aged >15 years) with HIV and antiretroviral therapy (ART) coverage. Estimates of CD4 less than 100 cells per μL, virological failure incidence, and loss to follow-up were from published multinational cohorts in low-income and middle-income countries. We calculated those at risk for cryptococcal infection, specifically those with CD4 less than 100 cells/μL not on ART, and those with CD4 less than 100 cells per μL on ART but lost to follow-up or with virological failure. Cryptococcal antigenaemia prevalence by country was derived from 46 studies globally. Based on cryptococcal antigenaemia prevalence in each country and region, we estimated the annual numbers of people who are developing and dying from cryptococcal meningitis. FINDINGS: We estimated an average global cryptococcal antigenaemia prevalence of 6·0% (95% CI 5·8-6·2) among people with a CD4 cell count of less than 100 cells per μL, with 278 000 (95% CI 195 500-340 600) people positive for cryptococcal antigen globally and 223 100 (95% CI 150 600-282 400) incident cases of cryptococcal meningitis globally in 2014. Sub-Saharan Africa accounted for 73% of the estimated cryptococcal meningitis cases in 2014 (162 500 cases [95% CI 113 600-193 900]). Annual global deaths from cryptococcal meningitis were estimated at 181 100 (95% CI 119 400-234 300), with 135 900 (75%; [95% CI 93 900-163 900]) deaths in sub-Saharan Africa. Globally, cryptococcal meningitis was responsible for 15% of AIDS-related deaths (95% CI 10-19). INTERPRETATION: Our analysis highlights the substantial ongoing burden of HIV-associated cryptococcal disease, primarily in sub-Saharan Africa. Cryptococcal meningitis is a metric of HIV treatment programme failure; timely HIV testing and rapid linkage to care remain an urgent priority. FUNDING: None

Normal-Mode Instabilities of a Time-Dependent Coastal Upwelling Jet

The linear stability of a nearly time-periodic, nonlinear, coastal upwelling–downwelling circulation, over alongshore-uniform topography, driven by a time-periodic wind stress is investigated using numerical methods. The near-periodic alongshore-uniform basic flow is obtained by forcing a primitive equation numerical model of coastal ocean circulation with periodic wind stress. Disturbance growth on this near-periodic flow is explored in linear and nonlinear model simulations. Numerous growing normal modes are found in the linear analyses at alongshore scales between 4 and 24 km. These modes vary in cross-shore structure and timing of maximum disturbance growth rate. One group of modes, in the 6.5–8.5-km alongshore-scale range, bears strong resemblance to the ensemble average disturbance structures observed in perturbed nonlinear model simulations. These modes are of a mixed type, exhibiting both strong baroclinic and barotropic energy exchange mechanisms, with maximum disturbance growth occurring during the transition from upwelling favorable to downwelling favorable winds. Nonlinear disturbance growth is characterized by similar structures at these same scales, but with significant exchange of energy between disturbances at different alongshore scales, such that overall disturbance energy accumulates at the longest (domain) scales, and gradually propagates offshore mainly in the pycnocline over numerous forcing cycl

Model-data synthesis and high resolution simulation of the Bering Sea

The Bering Sea is the source of over 50% of the total US fish catch and the home to immense populations of birds and marine mammals. This extraordinarily productive ecosystem is vulnerable to climate regime shifts that have occurred over the past decades. These regime shifts are closely linked to warming and cooling of the atmosphere and ocean, and the coincident retreat or expansion of the sea ice cover with strong interannual and decadal variability. Here we investigate changes in the Bering ice/ocean system in recent years. One of key tools for this investigation is the Bering Ecosystem STudy ice-ocean Modeling and Assimilation System (BESTMAS) for synthesis and modeling of the Bering ice/ocean system

Scale Evolution of Finite-Amplitude Instabilities on a Coastal Upwelling Front

Nonlinear model simulations of a coastal upwelling system show frontal instabilities that initiate at short alongshore scales but rapidly evolve to longer wavelengths. Several factors associated with the nonstationarity of this basic state contribute to the progression in scale. A portion of the system evolution is associated with the external forcing. Another portion is associated with the alteration of the alongshore mean flow resulting from wave growth. Direct interactions between the finite-amplitude disturbances also promote emergence of new scales. The relative role of each of these mechanisms is isolated through tangent linear simulations about basic states that approximate the nonlinear system to differing degrees. The basic states include an alongshore uniform time-evolving upwelling solution, the alongshore average of a three-dimensionally evolving upwelling solution, and the full three-dimensional nonlinear solution. Disturbance growth about a frozen-field upwelling state is also examined. Perturbation experiments are performed for persistent and relaxed wind forcing. Although the frontal disturbances in the nonlinear model exhibit a progression to larger scale over the full range of forcing scenarios considered, the mechanisms most responsible for the process differ between wind-forced and unforced cases. Under relaxed wind conditions, the perturbation growth experiments indicate that the scale evolution over the first four days is reflected in the way linear disturbances respond to the adjustment of an alongshore uniform upwelling front to wind cessation. The continued increase in scale between days 4 and 7 is related to the linear disturbance evolution on the alongshore average of a flow state that has been altered by wave–mean flow interaction. Past day 7, the observed scale change is not captured in the linear growth experiments and evidently results largely from nonlinear wave–wave interaction processes. Under sustained upwelling winds, the linear growth experiments fail to describe even the earliest scale change in the nonlinear solutions, indicating that nonlinear wave–wave effects are significant from very near the start of the simulations

All that glitters is not gold: high uptake on PSMA PET in non-prostate cancers does not mean that treatment with [<177Lu]Lu-PSMA-radioligand will be successful

Background The main objective is to discuss why treatment of non-prostate cancers with [177Lu]Lu-PSMAradioligand achieved only low tumor dose in most published cases, despite high uptake on PSMA PET. We use a patient with renal cell carcinoma as an illustrative example. Furthermore, we discuss how the problem with early washout and low tumor dose might be overcome by using a radionuclide with shorter half-life, matching the target binding residence time. Case presentation [ 68Ga]Ga-PSMA-11 PET/CT of a 56-year old man with metastatic renal cell carcinoma showed high lesion uptake. One dose of 6.9 GBq [177Lu]Lu-PSMA-I&T was administrated. Post-therapy dosimetry was performed with SPECT/CT and whole-body planar imaging after 5, 24 and 48 h. Doses to target lesions were only 0.2–0.5 Gy. No treatment effect was achieved. Conclusion Rapid tumor washout of [177Lu]Lu-PSMA-I&T and low tumor dose despite high uptake of [68Ga] Ga-PSMA-11 are most likely caused by localization of PSMA-receptors on neovasculature rather than on the tumor cells, and unlike in prostate cancer cells, the PSMA-RL / PSMA-receptor complex is not internalized. To overcome the problem with early washout, the use of a radionuclide with shorter half-life matching the target binding residence time will be needed

The baroclinic adjustment of time-dependent shear flows

Author Posting. © American Meteorological Society, 2010. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 40 (2010): 1851-1865, doi:10.1175/2010JPO4217.1.Motivated by the fact that time-dependent currents are ubiquitous in the ocean, this work studies the two-layer Phillips model on the beta plane with baroclinic shear flows that are steady, periodic, or aperiodic in time to understand their nonlinear evolution better. When a linearly unstable basic state is slightly perturbed, the primary wave grows exponentially until nonlinear advection adjusts the growth. Even though for long time scales these nearly two-dimensional motions predominantly cascade energy to large scales, for relatively short times the wave–mean flow and wave–wave interactions cascade energy to smaller horizontal length scales. The authors demonstrate that the manner through which these mechanisms excite the harmonics depends significantly on the characteristics of the basic state. Time-dependent basic states can excite harmonics very rapidly in comparison to steady basic states. Moreover, in all the simulations of aperiodic baroclinic shear flows, the barotropic component of the primary wave continues to grow after the adjustment by the nonlinearities. Furthermore, the authors find that the correction to the zonal mean flow can be much larger when the basic state is aperiodic compared to the periodic or steady limits. Finally, even though time-dependent baroclinic shear on an f plane is linearly stable, the authors show that perturbations can grow algebraically in the linear regime because of the erratic variations in the aperiodic flow. Subsequently, baroclinicity adjusts the growing wave and creates a final state that is more energetic than the nonlinear adjustment of any of the unstable steady baroclinic shears that are considered.FJP was supported by NSERC and JP was supported by NSF OCE 0925061 during the research and writing of this manuscript

Estimating the Benthic Efflux of Dissolved Iron on the Ross Sea Continental Shelf

Continental margin sediments provide a potentially large but poorly constrained source of dissolved iron (dFe) to the upper ocean. The Ross Sea continental shelf is one region where this benthic supply is thought to play a key role in regulating the magnitude of seasonal primary production. Here we present data collected during austral summer 2012 that reveal contrasting low surface (0.08 +/- 0.07 nM) and elevated near-seafloor (0.74 +/- 0.47 nM) dFe concentrations. Combining these observations with results from a high-resolution physical circulation model, we estimate dFe efflux of 5.8 x 10(7) mol yr(-1) from the deeper portions (\u3e400m) of the Ross Sea continental shelf; more than sufficient to account for the inferred winter reserve dFe inventory at the onset of the growing season. In addition, elevated dFe concentrations observed over shallower bathymetry suggest that such features provide additional inputs of dFe to the euphotic zone throughout the year