Dynamics of wind-forced coherent anticyclones in the open ocean

We numerically study the dynamics of coherent anticyclonic eddies in the ocean interior. For the hydrostatic, rotating, stably stratified turbulence we use a high-resolution primitive equation model forced by small-scale winds in an idealized configuration. Many properties of the horizontal motions are found to be similar to those of two-dimensional and quasi-geostrophic turbulence. Major differences are a strong cyclone-anticyclone asymmetry linked to the straining field exerted by vortex Rossby waves, which is also found in shallow water flows, and the complex structure of the vertical velocity field, which we analyze in detail. Locally, the motion can become strongly ageostrophic, and vertical velocities associated with vortices can reach magnitudes and levels of spatial complexity akin to those reported for frontal regions. Transport and mixing properties of the flow field are further investigated by analyzing Lagrangian trajectories. Particles released in the pycnocline undergo large vertical excursions because of the vertical velocities associated to the vortices, with potentially important consequences for marine ecosystem dynamics

Deep convection simulation from the MITgcm (MIT General Circulation Model) (IVOMLS project)

Dataset: Deep convection simulation using MITgcmAll experiments are preformed using the MIT General Circulation Model (MITgcm). The model is configured to allow non-hydrostatic dynamics to explicitly resolve deep convection. The model domain is a box with periodic boundary conditions in the x and y directions of 32 x 32 km with horizontal resolution of 250 m. The box has a uniform depth of 2 km with 41 z-levels whose thicknesses increases from 10 m at surface to 100 m near the bottom. The linear equation of state is used throughout this study. 16 sensitivity experiments are designed to explore the behavior of oxygen uptake during the deep convection events under different cooling conditions. Two validation runs are also applied by forcing the model using observational data from Argo. In this data set, horizontally averaged profiles and vertical transport of dissolved oxygen and temperature from all experiments are included. A few transect of dissolved oxygen and temperature are also included to demonstrate the evolution of the convection event. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/706167NSF Division of Ocean Sciences (NSF OCE) OCE-135737

Eddy formation near the west coast of Greenland

Author Posting. © American Meteorological Society, 2008. 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 38 (2008): 1992-2002, doi:10.1175/2008JPO3669.1.This paper extends A. Bracco and J. Pedlosky’s investigation of the eddy-formation mechanism in the eastern Labrador Sea by including a more realistic depiction of the boundary current. The quasigeostrophic model consists of a meridional, coastally trapped current with three vertical layers. The current configuration and topographic domain are chosen to match, as closely as possible, the observations of the boundary current and the varying topographic slope along the West Greenland coast. The role played by the bottom-intensified component of the boundary current on the formation of the Labrador Sea Irminger Rings is explored. Consistent with the earlier study, a short, localized bottom-trapped wave is responsible for most of the perturbation energy growth. However, for the instability to occur in the three-layer model, the deepest component of the boundary current must be sufficiently strong, highlighting the importance of the near-bottom flow. The model is able to reproduce important features of the observed vortices in the eastern Labrador Sea, including the polarity, radius, rate of formation, and vertical structure. At the time of formation, the eddies have a surface signature as well as a strong circulation at depth, possibly allowing for the transport of both surface and near-bottom water from the boundary current into the interior basin. This work also supports the idea that changes in the current structure could be responsible for the observed interannual variability in the number of Irminger Rings formed.AB is supported by WHOI unrestricted funds, JP by the National Science Foundation OCE 85108600, and RP by 0450658

Different Effects of High and Low Shear Stress on Platelet-Derived Growth Factor Isoform Release by Endothelial Cells

In the present study, we analyzed the effect of conditioned media (CM) from bovine aortic endothelial cells exposed to laminar shear stress (SS) of 5 dyne/cm 2 (SS5) or 15 dyne/cm 2 (SS15) for 16 hours on smooth muscle cell (SMC) migration. In response to CM from bovine aortic endothelial cells exposed to SS5 (CMSS5) and SS15 (CMSS15), migration was 45±5.5 and 30±1.5 cells per field, respectively ( P <0.05). Similar results were obtained with SS of 2 versus 20 dyne/cm 2 and also when SS of 5 and 15 dyne/cm 2 lasted 24 hours. Platelet-derived growth factor (PDGF)-AA levels in CMSS5 and CMSS15 were 9±7 and 18±5 ng/10 6 cells for 16 hours, respectively ( P <0.05); PDGF-BB levels in CMSS5 and CMSS15 were 38±10 and 53±10 ng/10 6 cells for 16 hours, respectively ( P CMSS5. In response to CMSS15, a neutralizing antibody against PDGF-AA enhanced SMC migration to a level comparable to that of CMSS5; in contrast, antibodies against PDGF-BB abolished SMC migration. Transfection of SMCs with a dominant-negative PDGFRα or PDGFRβ increased or inhibited, respectively, SMC migration in response to CMSS15. Overexpression of wild-type PDGFRα inhibited SMC migration in response to CMSS5, CMSS15, or recombinant PDGF-BB ( P <0.001). These results suggest that the ability of high SS to inhibit arterial wall thickening in vivo may be related to enhanced activation of PDGFRα in SMCs by PDGF isoforms secreted by the endothelium

Sustained growth of the Southern Ocean carbon storage in a warming climate

Abstract We investigate the mechanisms controlling the evolution of Southern Ocean carbon storage under a future climate warming scenario. A subset of Coupled Model Intercomparison Project Phase 5 models predicts that the inventory of biologically sequestered carbon south of 40°S increases about 18-34 Pg C by 2100 relative to the preindustrial condition. Sensitivity experiments with an ocean circulation and biogeochemistry model illustrates the impacts of the wind and buoyancy forcings under a warming climate. Intensified and poleward shifted westerly wind strengthens the upper overturning circulation, not only leading to an increased uptake of anthropogenic CO 2 but also releasing biologically regenerated carbon to the atmosphere. Freshening of Antarctic Surface Water causes a slowdown of the lower overturning circulation, leading to an increased Southern Ocean biological carbon storage. The rectified effect of these processes operating together is the sustained growth of the carbon storage in the Southern Ocean, even under the warming climate with a weaker global ocean carbon uptake

Transport, fate and impacts of the deep plume of petroleum hydrocarbons formed during the Macondo blowout

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bracco, A., Paris, C. B., Esbaugh, A. J., Frasier, K., Joye, S. B., Liu, G., Polzin, K. L., & Vaz, A. C. Transport, fate and impacts of the deep plume of petroleum hydrocarbons formed during the Macondo blowout. Frontiers in Marine Science, 7, (2020): 542147, doi:10.3389/fmars.2020.542147.The 2010 Macondo oil well blowout consisted in a localized, intense infusion of petroleum hydrocarbons to the deep waters of the Gulf of Mexico. A substantial amount of these hydrocarbons did not reach the ocean surface but remained confined at depth within subsurface plumes, the largest and deepest of which was found at ∼ 1000–1200 m of depth, along the continental slope (the deep plume). This review outlines the challenges the science community overcame since 2010, the discoveries and the remaining open questions in interpreting and predicting the distribution, fate and impact of the Macondo oil entrained in the deep plume. In the past 10 years, the scientific community supported by the Gulf of Mexico Research Initiative (GoMRI) and others, has achieved key milestones in observing, conceptualizing and understanding the physical oceanography of the Gulf of Mexico along its northern continental shelf and slope. Major progress has been made in modeling the transport, evolution and degradation of hydrocarbons. Here we review this new knowledge and modeling tools, how our understanding of the deep plume formation and evolution has evolved, and how research in the past decade may help preparing the scientific community in the event of a future spill in the Gulf or elsewhere. We also summarize briefly current knowledge of the plume fate – in terms of microbial degradation and geochemistry – and impacts on fish, deep corals and mammals. Finally, we discuss observational, theoretical, and modeling limitations that constrain our ability to predict the three-dimensional movement of waters in this basin and the fate and impacts of the hydrocarbons they may carry, and we discuss research priorities to overcome them.This review was made possible by funding from the Gulf of Mexico Research Initiative (GoMRI) and is a product of the Core Area 1 Synthesis workshop. The authors have contributed research on the Gulf deep circulation and the deep plume through GoMRI-funded consortia (ECOGIG for AB, SJ and GL, C-IMAGE for CP, AV and KF, and RECOVER for AE) and one of the RFP-5 grant (KP). KP was partially supported also by NSF OCE-1536779

Horizontal advection, diffusion, and plankton spectra at the sea surface

Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 114 (2009): C02001, doi:10.1029/2007JC004671.Plankton patchiness is ubiquitous in the oceans, and various physical and biological processes have been proposed as its generating mechanisms. However, a coherent statement on the problem is missing, because of both a small number of suitable observations and an incomplete understanding of the properties of reactive tracers in turbulent media. It has been suggested that horizontal advection may be the dominant process behind the observed distributions of phytoplankton and zooplankton, acting to mix tracers with longer reaction times (Rt) down to smaller scales. Conversely, the relative distributions of sea surface temperature and phytoplankton has been attributed to small-scale upwelling, where tracers with longer Rt are able to homogenize more than those with shorter reaction times. Neither of the above mechanisms can explain simultaneously the (relative) spectral slopes of temperature, phytoplankton, and zooplankton. Here, with a simple advection model and a large suite of numerical experiments, we concentrate on some of the physical processes influencing the relative distributions of tracers at the ocean surface, and we investigate (1) the impact of the spatial scale of tracer supply, (2) the role played by coherent eddies on the distribution of tracers with different Rt, and (3) the role of diffusion (so far neglected). We show that diffusion determines the distribution of temperature, regardless of the nature of the forcing. We also find that coherent structures together with differential diffusion of tracers with different Rt impact the tracer distributions. This may help in understanding the highly variable nature of observed plankton spectra.This work was initiated at WHOI during the summer of 2006, while S.C. was a summer student fellow, partially funded by the NSF. A.B. is funded by NSF–OCE 0751775 and NSF–OCE 0815280, and C.P. is funded by NSF–PHY 0551164