Search Results
1. Introduction The mean jet and the low-frequency variability obtained with a “double-gyre model” (e.g., Dijkstra 2005 ; Dijkstra and Ghil 2005 ) of the Kuroshio Extension ( Pierini 2006 , hereafter P06 ) were recognized to be in significant agreement with both in situ and altimetric measurements. The meandering pattern of the modeled mean jet yields two main crests and other secondary features in very good agreement with the climatological surface dynamic height of Teague et al. (1990
1. Introduction The mean jet and the low-frequency variability obtained with a “double-gyre model” (e.g., Dijkstra 2005 ; Dijkstra and Ghil 2005 ) of the Kuroshio Extension ( Pierini 2006 , hereafter P06 ) were recognized to be in significant agreement with both in situ and altimetric measurements. The meandering pattern of the modeled mean jet yields two main crests and other secondary features in very good agreement with the climatological surface dynamic height of Teague et al. (1990
1. Introduction Lander (1994) first identified monsoon gyres in the northwest Pacific as a separate class of disturbance in a case study from 1991. Their primary characteristics were the exceptionally large diameter of the closed surface pressure contour, long lifetime, and relatively rare occurrence. Winds were typically light at the gyre center, and strongly asymmetric clouds and precipitation peaked south and east of the center. One consequence of the size of the gyre is that tropical
1. Introduction Lander (1994) first identified monsoon gyres in the northwest Pacific as a separate class of disturbance in a case study from 1991. Their primary characteristics were the exceptionally large diameter of the closed surface pressure contour, long lifetime, and relatively rare occurrence. Winds were typically light at the gyre center, and strongly asymmetric clouds and precipitation peaked south and east of the center. One consequence of the size of the gyre is that tropical
occurred at 40°S, where the 4 W m −2 of warming in the upper 750 m was more than 4 times the global average. In the present work, this spatial inhomogeneity in ocean warming is explained by the deepening of isopycnal surfaces that signal the spinup of deep ocean gyres. The most energetic patterns of extratropical variability in the lower atmosphere are the annular modes—the Northern Hemisphere annular mode (NAM), or Arctic Oscillation, and its counterpart, the Southern Hemisphere annular mode (SAM
occurred at 40°S, where the 4 W m −2 of warming in the upper 750 m was more than 4 times the global average. In the present work, this spatial inhomogeneity in ocean warming is explained by the deepening of isopycnal surfaces that signal the spinup of deep ocean gyres. The most energetic patterns of extratropical variability in the lower atmosphere are the annular modes—the Northern Hemisphere annular mode (NAM), or Arctic Oscillation, and its counterpart, the Southern Hemisphere annular mode (SAM
. The model described in this study is driven by both buoyancy forcing (in a simple parameterization of heating and cooling) and wind stress (Ekman pumping). The buoyancy forcing naturally suggests examining a double-gyre circulation consisting of simple representations of subtropical and subpolar gyres. It will be shown in the following that, when the island extends, even slightly, from one gyre into the other, that is, across the zero line of the forcing, the presence of the island induces a
. The model described in this study is driven by both buoyancy forcing (in a simple parameterization of heating and cooling) and wind stress (Ekman pumping). The buoyancy forcing naturally suggests examining a double-gyre circulation consisting of simple representations of subtropical and subpolar gyres. It will be shown in the following that, when the island extends, even slightly, from one gyre into the other, that is, across the zero line of the forcing, the presence of the island induces a
with observations from altimetry and current meters. For example, correlations between predicted transports and those derived from the principal EOF of sea surface height yielded coefficients of r = 0.76 in the Norwegian Gyre and r = 0.88 in the Greenland Gyre. Likewise, the correlation between the Norwegian gyre transport from the analytical model and that from a full primitive equation model was r = 0.75. So the analytical model appears to capture the dominant dynamics in these gyres
with observations from altimetry and current meters. For example, correlations between predicted transports and those derived from the principal EOF of sea surface height yielded coefficients of r = 0.76 in the Norwegian Gyre and r = 0.88 in the Greenland Gyre. Likewise, the correlation between the Norwegian gyre transport from the analytical model and that from a full primitive equation model was r = 0.75. So the analytical model appears to capture the dominant dynamics in these gyres
between 20° and 30°S being part of the northern branch of the South Atlantic subtropical gyre. A quantitative comparison of this flow shows that flow derived from float data has a mean speed of 4.7 ± 3.3 cm s −1 while that estimated from the inversion has a posterior mean speed of 3.3 cm s −1 and a posterior standard deviation of 0.6 cm s −1 . Using data compiled from Núñez-Riboni et al. (2005) , we converted the mean zonal transport across the South Atlantic Ocean into averaged mean velocities for
between 20° and 30°S being part of the northern branch of the South Atlantic subtropical gyre. A quantitative comparison of this flow shows that flow derived from float data has a mean speed of 4.7 ± 3.3 cm s −1 while that estimated from the inversion has a posterior mean speed of 3.3 cm s −1 and a posterior standard deviation of 0.6 cm s −1 . Using data compiled from Núñez-Riboni et al. (2005) , we converted the mean zonal transport across the South Atlantic Ocean into averaged mean velocities for
variability remains poorly understood. This variability had been first noted by Bryan (1963) , and the fundamental role of the mesoscale eddies in shaping the background flow was later emphasized by Holland (1978) . Since then, different variability patterns and mechanisms have been suggested on the basis of idealized gyre dynamics. One of the intensively studied ideas is that the ocean variability can be understood in terms of early bifurcations of the forced and dissipative dynamical systems ( Cessi
variability remains poorly understood. This variability had been first noted by Bryan (1963) , and the fundamental role of the mesoscale eddies in shaping the background flow was later emphasized by Holland (1978) . Since then, different variability patterns and mechanisms have been suggested on the basis of idealized gyre dynamics. One of the intensively studied ideas is that the ocean variability can be understood in terms of early bifurcations of the forced and dissipative dynamical systems ( Cessi
1. Introduction Wind stress curl at midlatitudes generates anticyclonic subtropical and cyclonic subpolar gyres (i.e., double gyres). Intensive boundary currents in the gyres appear at the western flank and enter into the open ocean as eastward jets. They carry substantial amounts of heat and momentum and strongly affect global climate. A typical example of such currents is the Kuroshio with a 100-km width and 2-m s −1 velocity at maximum. In the Kuroshio, we can observe several variations
1. Introduction Wind stress curl at midlatitudes generates anticyclonic subtropical and cyclonic subpolar gyres (i.e., double gyres). Intensive boundary currents in the gyres appear at the western flank and enter into the open ocean as eastward jets. They carry substantial amounts of heat and momentum and strongly affect global climate. A typical example of such currents is the Kuroshio with a 100-km width and 2-m s −1 velocity at maximum. In the Kuroshio, we can observe several variations
thermocline. However, Salmon and Hollerbach failed to obtain a two-gyre solution and speculated that it might represent a general limitation of the thermocline equations without horizontal diffusion. Hence, they suggested studying solutions where its role would be taken into account. Some of these solutions had been previously searched and found in a stationary context by Filippov (1968) . He listed four families of solutions where the horizontal diffusion was taken into account. These solutions were
thermocline. However, Salmon and Hollerbach failed to obtain a two-gyre solution and speculated that it might represent a general limitation of the thermocline equations without horizontal diffusion. Hence, they suggested studying solutions where its role would be taken into account. Some of these solutions had been previously searched and found in a stationary context by Filippov (1968) . He listed four families of solutions where the horizontal diffusion was taken into account. These solutions were
.g., interactions with topography, high-frequency winds, tides, etc.). The idea is to maintain a background field of 3D motion with which the 2D flow can interact. We are particularly interested in interactions where the 2D flow is energetic, since this is where we anticipate the interaction being strongest. For this reason, our large-scale 3D forcing is concentrated in the western portion of the basin, near the boundary layer confluence. The 2D modes are forced as in the classic double-gyre problem, (e
.g., interactions with topography, high-frequency winds, tides, etc.). The idea is to maintain a background field of 3D motion with which the 2D flow can interact. We are particularly interested in interactions where the 2D flow is energetic, since this is where we anticipate the interaction being strongest. For this reason, our large-scale 3D forcing is concentrated in the western portion of the basin, near the boundary layer confluence. The 2D modes are forced as in the classic double-gyre problem, (e
