The causes of full ocean depth interannual variability in Drake Passage

In recent years a number of large scale modes of Southern Hemisphere climate variability have been observed, most notably the Southern Annular Mode (SAM, e.g. Thompson and Solomon, 2002), the Pacific South American modes (PSA, e.g. Mo and Peagle, 2001), the Antarctic Dipole (e.g. Martinson and Ianuzzi, 2003), the Antarctic Circumpolar Wave (e.g. White and Peterson, 1996), and of course the El Niño Southern Oscillation (ENSO). All have pronounced effects over or in the Southern Ocean, and may be expected to account for a significant part of the interannual variability observed there. Most studies analyse these phenomena from a large-scale point of view, often by extracting modes from Southern Hemisphere atmospheric and oceanic fields using various mathematical techniques. In this study we have taken an alternative approach, and tried to understand the causes of the full ocean depth variability in Drake Passage observed in the WOCE SR1b repeat hydrographic sections (Cunningham et al. 2003)

Praticando a Responsabilidade Social Universitária no Caribe: Perspectiva do público interno

University Social Responsibility (USR) is the ethical and transparent management of the administrative, educational, cognitive and social processes carried out by a higher education institution. More and more universities are practicing USR not only in Latin America but also in the United States and Europe, in order to reduce the negative impacts their daily operations can have on different stakeholders and on a macro level on society, the economy, and the environment. However, despite existing knowledge in the implementation of USR in Latin America and the Caribbean, there are few empirical studies that analyze the positions of diverse internal stakeholders regarding USR practices mainly in the Caribbean. Therefore, this study analyzes the perspectives of the internal stakeholders in social responsibility initiatives and processes at a private university in Puerto Rico. A total of 533 participants (356 students, 99 administrative staff, and 78 faculty members) were interviewed and were given a questionnaire, which evaluated the following areas: responsible campus, professional and citizenship education, social knowledge management, and social participation. Overall, the internal stakeholders’ perceptions were consistent among the three groups. It can be observed that the various internal stakeholders are aware of what it means—in theory, and in practice—, to be a socially-responsible university, although they also recognize opportunities for improvement and future challenges regarding USR. The results of this study contribute to the literature, to the application of conceptual models—mainly from the perspectives of internal stakeholders—and to the importance of evaluating USR practices.La responsabilidad social universitaria (RSU) es la gestión ética y transparente de los procesos administrativos, educativos, cognitivos y sociales que realiza una institución de educación superior. Cada vez más son las universidades que practican la RSU no solo en Latinoamérica sino también en Estados Unidos y Europa, esto con el fin de reducir los impactos negativos que causan las operaciones diarias en distintos públicos de interés y a nivel macro en la sociedad, economía y el medioambiente. No obstante, a pesar del conocimiento que existe sobre la práctica de RSU en Latinoamérica y El Caribe, existen pocos estudios empíricos que analicen las posturas de diversos públicos internos respecto a las prácticas de RSU principalmente en El Caribe. Por ello, este estudio analiza las perspectivas de públicos internos sobre las iniciativas y procesos de responsabilidad social en una universidad privada en Puerto Rico. Se evalúo a un total de 533 participantes (356 estudiantes, 99 administrativos y 78 profesores) a los cuales se les aplicó un cuestionario que evaluaba las siguientes áreas: campus responsable, educación profesional y ciudadana, gestión de conocimiento social y participación social. En general, las percepciones públicas internas fueron consistentes entre los tres grupos. Se aprecia que los diversos públicos internos están conscientes de lo que significa, en la teoría y en la práctica, ser una universidad socialmente responsable aunque también reconocen oportunidades de mejora y desafíos futuros con respecto a la RSU. Los resultados de este estudio aportan a la literatura, la aplicación de modelos conceptuales, principalmente desde perspectivas de públicos internos y la importancia de evaluar las prácticas de RSU.A Responsabilidade Social Universitária (RSU) é a gestão ética e transparente dos processos administrativos, educacionais, cognitivos e sociais realizadas por uma instituição de ensino superior. Mais e mais universidades que praticam RSU não só na América Latina, mas também nos Estados Unidos e na Europa, este, a fim de reduzir os impactos negativos causados pelas operações diárias em várias partes interessadas e ao nível macro na sociedade, economia e o meio ambiente. No entanto, apesar do conhecimento que existe sobre a prática da RSU na América Latina e no Caribe, há poucos estudos empíricos que analisam as posições dos diversos públicos internos sobre as práticas de RSU principalmente no Caribe. Portanto, este estudo analisa as perspectivas de públicos internos sobre as iniciativas e processos de responsabilidade social em uma universidade privada em Puerto Rico. Foram avaliados um total de 533 participantes (356 alunos, 99 administrativos e 78 professores) ao qual foi aplicado um questionário avaliando as seguintes áreas: campus de educação responsável, profissional e pública, gestão do conhecimento social e de participação social. Em geral, as percepções do público interno foram consistentes entre os três grupos. Reconhece-se que os vários públicos internos estão cientes do que significa, na teoria e na prática, ser uma universidade socialmente responsável, mas também reconhecem as oportunidades de melhoria e os desafios futuros a respeito da RSU. Os resultados deste estudo contribuem para a literatura, a aplicação de modelos conceituais, principalmente a partir de perspectivas do público interno e a importância de avaliar as práticas de RSU

Temporal Variability of Diapycnal Mixing in Shag Rocks Passage

Diapycnal mixing rates in the oceans have been shown to have a great deal of spatial variability, but the temporal variability has been little studied. Here we present results from a method developed to calculate diapycnal diffusivity from moored Acoustic Doppler Current Profiler (ADCP) velocity shear profiles. An 18-month time series of diffusivity is presented from data taken by a LongRanger ADCP moored at 2400 m depth, 600 m above the sea floor, in Shag Rocks Passage, a deep passage in the North Scotia Ridge (Southern Ocean). The Polar Front is constrained to pass through this passage, and the strong currents and complex topography are expected to result in enhanced mixing. The spatial distribution of diffusivity in Shag Rocks Passage deduced from lowered ADCP shear is consistent with published values for similar regions, with diffusivity possibly as large as 90 × 10-4 m2 s-1 near the sea floor, decreasing to the expected background level of ~ 0.1 × 10-4 m2 s-1 in areas away from topography. The moored ADCP profiles spanned a depth range of 2400 to 1800 m; thus the moored time series was obtained from a region of moderately enhanced diffusivity. The diffusivity time series has a median of 3.3 × 10-4 m2 s-1 and a range of 0.5 × 10-4 m2 s-1 to 57 × 10-4 m2 s-1. There is no significant signal at annual or semiannual periods, but there is evidence of signals at periods of approximately fourteen days (likely due to the spring-neaps tidal cycle), and at periods of 3.8 and 2.6 days most likely due to topographically-trapped waves propagating around the local seamount. Using the observed stratification and an axisymmetric seamount, of similar dimensions to the one west of the mooring, in a model of baroclinic topographically-trapped waves, produces periods of 3.8 and 2.6 days, in agreement with the signals observed. The diffusivity is anti-correlated with the rotary coefficient (indicating that stronger mixing occurs during times of upward energy propagation), which suggests that mixing occurs due to the breaking of internal waves generated at topography

Probing vortex-shedding at high frequencies in flows past confined microfluidic cylinders using high-speed microscale particle image velocimetry

Vortex-shedding from micropins has the potential to significantly enhance and intensify scalar transport in microchannels, for example by improving species mixing. However, the onset of vortex-shedding and the mixing efficiency are highly sensitive to the confinement imposed by the microchannel walls. In this work, the time dependent flow past a cylindrical pin in microchannels with different levels of confinement was studied experimentally. The onset of vortex-shedding in such flows is associated with high, kilohertz range frequencies that are difficult to resolve using conventional laser-based microscale particle image velocimetry (μPIV) techniques. Hence, in this study, a high-speed μPIV technique was implemented in order to obtain time-resolved measurements of the velocity fields downstream of the micropin to estimate the corresponding vortex-shedding frequencies and quantify the mixing in the pin wake. The vertical confinement (pin length to diameter ratio) was found to delay the onset of vortex-shedding. When vortex-shedding was present, the shedding frequency and the corresponding Strouhal numbers were found to be greater in channels with higher lateral confinement for the same Reynolds number. Finite-time Lyapunov exponent analysis was performed on the acquired velocity fields to estimate the mixing performance. The results clearly illustrated the significant enhancement in both the mixing in the wake and the mass flux across the centerline of the wake induced by vortex-sheddin

Canonical connection on a class of Riemannian almost product manifolds

The canonical connection on a Riemannian almost product manifold is an analogue to the Hermitian connection on an almost Hermitian manifold. In this paper we consider the canonical connection on a class of Riemannian almost product manifolds with non-integrable almost product structure. We construct and characterize an example by a Lie group.Comment: 19 pages, some corrections in the example; J. Geom. (2012

Observation of a large lee wave in the Drake Passage

Lee waves are thought to play a prominent role in Southern Ocean dynamics, facilitating a transfer of energy from the jets of the Antarctic Circumpolar Current to microscale, turbulent motions important in water mass transformations. Two EM-APEX profiling floats deployed in the Drake Passage during the Diapycnal and Isopycnal Mixing Experiment (DIMES) independently measured a 120 ± 20-m vertical amplitude lee wave over the Shackleton Fracture Zone. A model for steady EM-APEX motion is developed to calculate absolute vertical water velocity, augmenting the horizontal velocity measurements made by the floats. The wave exhibits fluctuations in all three velocity components of over 15 cm s−1 and an intrinsic frequency close to the local buoyancy frequency. The wave is observed to transport energy and horizontal momentum vertically at respective peak rates of 1.3 ± 0.2 W m−2 and 8 ± 1 N m−2. The rate of turbulent kinetic energy dissipation is estimated using both Thorpe scales and a method that isolates high-frequency vertical kinetic energy and is found to be enhanced within the wave to values of order 10−7 W kg−1. The observed vertical flux of energy is significantly larger than expected from idealized numerical simulations and also larger than observed depth-integrated dissipation rates. These results provide the first unambiguous observation of a lee wave in the Southern Ocean with simultaneous measurements of its energetics and dynamics