Ocean general circulation from a global eddy-resolving model

A concerted effort has been made to simulate the global ocean circulation with resolved eddies, using a highly optimized model on the best available supercomputer. An earlier 20-year spin-up has been extended for 12.5 additional years: the first 2.5 with continued annual mean forcing and the final 10.0 with climatological monthly forcing. Model output achived at 3-day intervals, has been analyzed into mean fields, standard deviations, products, and covariances on monthly, annual and multiyear time scales. The multiyear results are examined here in order to give insight into the general circulation of the world ocean. The three-dimensional flow fields of the model are quite realistic, even though resolution of eddies in high latitudes is marginal with a 0.5 degree, 20-level grid. The use of seasonal forcing improves the simulation, especially in the tropics and high northern latitudes. Mid-latitude gyre circulations, western boundary currents, zonal equatorial flows, and the Antarctic Circumpolar Current (ACC) all show mean and eddy characteristics similar to those observed. There is also some indication of eddy intensification of the mean flow of the ACC and of separated boundary jets. A global thermohaline circulation of North Atlantic Deep Water is identified in deep western boundary currents connected by the ACC. This deep circulation rises mainly in the equatorial Pacific. Several zonal jets are an integral part of ths circulation near the equator. The deep flow rises toward the surface in a series of switchbacks. Much of the thermohaline return flow then follows an eddy-rich warm-water route through the Indonesian archipelago and around the southern tip of Africa. However, some intermediate level portions of the thermohaline circulation return south into the ACC and follow a cold water route through the Drake Passage. The representation of a global "conveyer belt" circulation with narrow and reltively high-speed currents along most of its path may be the most important result of this modeling study. Statistics of scalar fields such as transport stream function and surface height are exhibited, as are time series and frequency spectra of certain variables at selected points. These provide a baseline for comparison both with observations and with other model studies at higher resolution. Mean and eddy characteristics of the near-surface temperature and salinity fields are discussed, and surface forcing fields are examined. In particular, combined thermal and hydrological forcing effects are found to drive a conveyor belt circulation between the tropical Pacific and the high-latitude North Atlantic. The effect of weak restoring terms to observed temperature and salinity at great depth and in polar latitudes is found mainly to augment the model's convective processes, which are poorly resolved with a 0.5 degree grid spacing. However, the deep restoring terms are insignificant in both the tropics and in the mid-latitudes. The geographical distributions of eddy heat and salt transport are discussed. The eddies transport heat and salt down the gradients and along the mean flow in many regions of strong currents. Net meridional transports of heat and salt by both the total currents and the eddies are computed for the Atlantic, the Indo-Pacific, and the global ocean. The total currents provide for poleward heat transport (except near 40 degrees S, where the contribution from ACC instabilities is rather weak) and, in particular, for that needed to sustain the conveyor belt transport. Meridional eddy transports are especially important for warming the Pacific upwelling branch of the thermohaline circulation and for transporting salt across the equator into the North Pacific. Planned improvements to the model include a free-surface treatment of the barotropic mode and additions of the Arctic Basin and sea ice. A fully prognostic extension of the existing integration is intended, with subsequent transitioning of the model onto a 0.25 degree grid having very realistic geometry. The 0.25 degree version of the model will run effectively on newly available supercomputers

A factorial analysis of the marine carbon cycle controls on atmospheric CO2

A factorial experiment with a new Earth system model of intermediate complexity is used to assess the sensitivity of atmospheric CO2 to organic, carbonate and solubility pumps, ocean circulation state, and climate feedback. An analysis of variance of the results reveals that the organic, carbonate, and solubility pumps act multiplicatively and account for 94% of the variance of atmospheric CO2. The organic pump explains 63% (89 ppm), the solubility pump 24% (55 ppm), the carbonate pump 6% (28 ppm), and ocean circulation 0.3% (12 ppm) of the variance. Removing all pumps increases atmospheric CO2 from 278 to 525 ppm. Including interactions with all the pumps increases the effects of ocean circulation from 12 to 56 ppm. However, the ocean circulation states used are unlikely to span the full range of possible states. Changes in Pacific circulation have more effect on atmospheric CO2 than Atlantic circulation

Estimates of anthropogenic carbon uptake from four three-dimensional global ocean models

We have compared simulations of anthropogenic CO$_2$ in the four threedimensional ocean models that participated in the first phase of the Ocean Carbon-Cycle Model Intercomparison Project (OCMIP), as a means to identify their major differences.Simulated global uptake agrees to within $\pm$19%, giving a range of 1.85$\pm$0.35 PgC yr$^{-1}$ for the 1980-1989 average. Regionally, the Southern Ocean dominates the present-day air-sea flux of anthropogenic CO$_2$ in all models, with one third to one half of the global uptake occurring south of 30°S. The highest simulated total uptake in the Southern Ocean was 70% larger than the lowest. Comparison with recent data-based estimates of anthropogenic CO$_2$ suggesthat most of the models substantially overestimate storage in the Southern Ocean; elsewhere they generally underestimate storage by less than 20%. Globally, the OCMIP models appear to bracket the real ocean's present uptake, based on comparison of regional data-basedstimates of anthropogenic CO$_2$ and bomb $^{14}$C. Column inventories of bomb $^{14}$C have become more similar to those for anthropogenic CO$_2$ with the time that has elapsed between the Geochemical Ocean Sections Study (1970s) and Word Ocean Circulation Experiment (1990s) global sampling campaigns. Our ability to evaluate simulated anthropogenic CO$_2$ would improve if systematic errors associated with the data-based estimates could be provided regionally

Transcatheter aortic valve replacement with a new self-expanding transcatheter heart valve and motorized delivery system

OBJECTIVES: The aim of this study was to demonstrate feasibility and short- and midterm clinical outcomes with a new self-expanding transcatheter heart valve and motorized delivery system. BACKGROUND: Refining transcatheter aortic valve replacement with newly designed bioprostheses and delivery systems is anticipated to facilitate the procedure, reduce the risk of complications, improve outcomes, and widen applicability. METHODS: The CENTERA valve (Edwards Lifesciences, Irvine, California) was implanted in 15 patients with symptomatic severe aortic stenosis via femoral or axillary arterial percutaneous access. Patients underwent transesophageal echocardiography during and transthoracic echocardiography and multidetector computed tomography before and after valve implantation. Clinical and echocardiographic follow-up was obtained at 30 days and for the initial 10 patients after 1 year. RESULTS: All 15 device implants were successful. Aortic valve area increased from 0.7 ± 0.1 cm(2) to 1.6 ± 0.4 cm(2) post-procedure (p < 0.01) and 1.8 ± 0.3 cm(2) at 1 year. Mean transaortic gradient decreased from 36.3 ± 14.2 mm Hg to 10.6 ± 5.4 mm Hg post-procedure (p < 0.001) and 10.8 ± 4.1 mm Hg at 1 year. Paravalvular aortic regurgitation at 30-day follow-up was none/trivial in 3 (23%), mild in 9 (69%), and moderate in 1 (8%) patient. Four patients (27%) received a new permanent pacemaker. Survival was 87% at 30 days and 80% at 1 year. All surviving patients were in New York Heart Association functional class I (25%) or II (75%) at 1 year. CONCLUSIONS: Transcatheter aortic valve replacement with the CENTERA transcatheter heart valve and motorized delivery system is feasible and can lead to good short- and midterm clinical and hemodynamic outcomes

Comparison of Lipid Deposition at Coronary Bifurcations Versus at Nonbifurcation Portions of Coronary Arteries as Determined by Near-Infrared Spectroscopy

Atherosclerosis has been shown to develop preferentially at sites of coronary bifurcation, yet culprit lesions resulting in ST-elevation myocardial infarction do not occur more frequently at these sites. We hypothesized that these findings can be explained by similarities in intracoronary lipid and that lipid and lipid core plaque would be found with similar frequency in coronary bifurcation and nonbifurcation segments. One hundred seventy bifurcations were identified, 156 of which had comparative nonbifurcation segments proximal and/or distal to the bifurcation. We compared lipid deposition at bifurcation and nonbifurcation segments in coronary arteries using near-infrared spectroscopy (NIRS), a novel method for the in vivo detection of coronary lipid. Any NIRS signal for the presence of lipid was found with similar frequency in bifurcation and nonbifurcation segments (79% vs 74%, p = NS). Lipid core burden index, a measure of total lipid quantity indexed to segment length, was similar across bifurcation segments as well as their proximal and distal controls (lipid core burden index 66.3 ± 106, 67.1 ± 116, and 66.6 ± 104, p = NS). Lipid core plaque, identified as a high-intensity focal NIRS signal, was found in 21% of bifurcation segments, and 20% of distal nonbifurcation segments (p = NS). In conclusion, coronary bifurcations do not appear to have higher levels of intracoronary lipid or lipid core plaque than their comparative nonbifurcation regions