Interior pathways of the North Atlantic meridional overturning circulation

To understand how our global climate will change in response to natural and anthropogenic forcing, it is essential to determine how quickly and by what pathways climate change signals are transported throughout the global ocean, a vast reservoir for heat and carbon dioxide. Labrador Sea Water (LSW), formed by open ocean convection in the subpolar North Atlantic, is a particularly sensitive indicator of climate change on interannual to decadal timescales. Hydrographic observations made anywhere along the western boundary of the North Atlantic reveal a core of LSW at intermediate depths advected southward within the Deep Western Boundary Current (DWBC). These observations have led to the widely held view that the DWBC is the dominant pathway for the export of LSW from its formation site in the northern North Atlantic towards the Equator. Here we show that most of the recently ventilated LSW entering the subtropics follows interior, not DWBC, pathways. The interior pathways are revealed by trajectories of subsurface RAFOS floats released during the period 2003-2005 that recorded once-daily temperature, pressure and acoustically determined position for two years, and by model-simulated 'e-floats' released in the subpolar DWBC. The evidence points to a few specific locations around the Grand Banks where LSW is most often injected into the interior. These results have implications for deep ocean ventilation and suggest that the interior subtropical gyre should not be ignored when considering the Atlantic meridional overturning circulation.Dissertatio

Verifique sus conocimientos sobre técnicas de diagnóstico por la imagen en patología dental y maxilofacial

Esta entrega, que forma parte de una serie de Nursing sobre las pruebas complementarias, está dedicada a las técnicas de imagen para la exploración dental. La exploración y el diagnóstico se pueden llevar a cabo mediante diferentes modalidades diagnósticas. Las más habituales son la radiología convencional, la tomografía computarizada (TC) y la resonancia magnética (RM). Para facilitar a los profesionales de enfermería los recursos necesarios para satisfacer las demandas de información de los pacientes, es necesario un recorrido por estas técnicas, habituales en los diferentes ámbitos asistenciales. Desde el punto de vista de atención al paciente es útil poder explicar y despejar las dudas que se pudieran plantear respecto a la preparación, a la dinámica y, en general, al proceso diagnóstico

Heat transport in horizontal and inclined convection

We discuss three classical paradigmatic systems of thermally driven flows: Rayleigh-Benard convection, where a fluid is confined between a heated bottom plate and a cooled top plate, horizontal convection, where the fluid is heated at one part of the bottom and cooled at some other part, and vertical convection, where the fluid is confined between two differently heated isothermal vertical plates. Rayleigh-Benard and vertical convection can be also considered as limiting cases of so-called inclined convection. For these systems we study how the heat and momentum transport, which is represented by the Nusselt number and Reynolds number, scales with the main governing parameters of the system, which are the Rayleigh number and Prandtl number. We show that different boundary conditions generally lead to different scaling diagrams in the Prandtl-Rayleigh plane. For laminar vertical convection the scalings can be derived from the boundary layer equations, see Shishkina (Phys Rev E 93: 051102, 2016, [8]). In the case of horizontal convection, the scalings can be derived from the analysis of the boundary-layer and bulk contributions of the kinetic and thermal dissipation rates, see Shishkina et al. (Geophys Res Lett 43: 1219-1225, 2016, [5]). Here we summarize some previous results and discuss the applicability of the developed theory to global ocean circulation

Directly measured mid-depth circulation in the northeastern North Atlantic Ocean

The circulation of water masses in the northeastern North Atlantic Ocean has a strong influence on global climate owing to the northward transport of warm subtropical water to high latitudes. But the ocean circulation at depths below the reach of satellite observations is difficult to measure, and only recently have comprehensive, direct observations of whole ocean basins been possible. Here we present quantitative maps of the absolute velocities at two levels in the northeastern North Atlantic as obtained from acoustically tracked floats. We find that most of the mean flow transported northward by the Gulf Stream system at the thermocline level (about 600 m depth) remains within the subpolar region, and only relatively little enters the Rockall trough or the Nordic seas. Contrary to previous work, our data indicate that warm, saline water from the Mediterranean Sea reaches the high latitudes through a combination of narrow slope currents and mixing processes. At both depths under investigation, currents cross the Mid-Atlantic Ridge preferentially over deep gaps in the ridge, demonstrating that sea-floor topography can constrain even upper-ocean circulation patterns