scholarly journals Shelf Currents within Different Oceans Under the Sun-Moon Gravitation

2019 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Gulf Stream ◽  
Western Boundary ◽  
The Sun ◽  
Dynamical Equations ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
The Kuroshio

Here, I employed the shelf properties and sizes of different basins and introduced the Sun-Moon gravitation into the dynamical equations to dynamically explain the differences existing in the Gulf Stream and the Kuroshio systems. In addition to the classic western-boundary intensification of the western boundary currents that fails to explain why the differences in currents and ENSO significance exist among different oceans, shelf properties and sizes of different basins may produce another westernboundary intensification of the western boundary currents under the Sun-Moon gravitation.

Mean and eddy kinetic energy of the Gulf Stream from multiyear underwater glider surveys

2020 ◽  
Author(s):  
Robert E. Todd
Keyword(s):  
Kinetic Energy ◽  
Gulf Stream ◽  
Three Dimensional ◽  
Eddy Kinetic Energy ◽  
Cape Cod ◽  
Western Boundary ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
Global Circulation Models ◽  
The North

<p>Subtropical western boundary currents play a key role in ocean energy storage and transport and are characterized by elevated mean and eddy kinetic energy. Due to a lack of spatially broad subsurface observations of velocity, most studies of kinetic energy in western boundary currents have relied on satellite-based estimates of surface geostrophic velocity. Since 2015, Spray autonomous underwater gliders have completed more than 175 crossings of the Gulf Stream distributed over more than 1,500 km in along-stream extent between between Miami, FL (~25°N) and Cape Cod, MA (~40°N). The observations include roughly 14,000 absolute ocean velocity profiles in the upper 1000 m. Novel three-dimensional estimates of mean and eddy kinetic energy are constructed along the western margin of the North Atlantic at 10-m vertical resolution. The horizontal and vertical distributions of mean and eddy kinetic energy are analyzed in light of existing independent estimates and theoretical expectations. Observation-based estimates of mean and eddy-kinetic energy such as these serve as important metrics for validation of global circulation models that must adequately represent western boundary currents.</p>

scholarly journals Role of Kuroshio Current in fish resource variability off southwest Japan

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yushi Morioka ◽  
Sergey Varlamov ◽  
Yasumasa Miyazawa
Keyword(s):  
Rossby Waves ◽  
Kuroshio Current ◽  
Temperature Variability ◽  
Western Boundary ◽  
Ocean Temperature ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
Subsurface Ocean ◽  
Resource Variability ◽  
The Kuroshio

AbstractWestern boundary currents in the subtropics play a pivotal role in transporting warm water from the tropics that contribute to development of highly diverse marine ecosystem in the coastal regions. As one of the western boundary currents in the North Pacific, the Kuroshio Current (hereafter the Kuroshio) exerts great influences on biological resource variability off southwest Japan, but few studies have examined physical processes that attribute the coastal fish resource variability to the basin-scale Kuroshio variability. Using the high-quality fish catch data and high-resolution ocean reanalysis results, this study identifies statistical links of interannual fish resource variability off Sukumo Bay, Shikoku island of Japan, to subsurface ocean temperature variability in the Kuroshio. The subsurface ocean temperature variability off the south of Sukumo Bay exhibits vertically coherent structure with sea-surface height variability, which originates from the westward-propagating oceanic Rossby waves generated through surface wind anomalies in the Northwest Pacific. Although potential sources of the atmospheric variability remain unclarified, the remotely-induced oceanic Rossby waves contribute to fish resource variability off Sukumo Bay. These findings have potential applications to other coastal regions along the western boundary currents in the subtropics where the westward-propagating oceanic Rossby waves may contribute to coastal ocean temperature variability.

Dynamics of Gap-leaping Western Boundary Currents with Throughflow Forcing

2021 ◽  
Author(s):  
Charles W. McMahon ◽  
Joseph J. Kuehl ◽  
Vitalii A. Sheremet
Keyword(s):  
Particle Tracking Velocimetry ◽  
Numerical Models ◽  
Western Boundary ◽  
Loop Current ◽  
Western Boundary Currents ◽  
Nonlinear Dynamical ◽  
Boundary Currents ◽  
Lab Experiments ◽  
Experimental Apparatus ◽  
The Kuroshio

AbstractThe dynamics of gap-leaping western boundary currents (e.g. the Kuroshio intrusion, the Loop Current) are explored through rotating table experiments and a numerical model designed to replicate the experimental apparatus. Simplified experimental and numerical models of gap-leaping systems are known to exhibit two dominant states (leaping or penetrating into the gap) as the inertia of the current competes with vorticity constraints (in this case the β-effect). These systems are also known to admit multiple states with hysteresis. To advance towards more realistic oceanographic scenarios, recent studies have explored the effects of islands, mesoscale eddies, and variable baroclinic deformation radii on the dynamical system. Here, the effect of throughflow forcing is considered, with particle tracking velocimetry (PTV) used in the lab experiments. Mean transport in or out of the gap is found to significantly shift the hysteresis range as well as change its width. Because of these transformations, changes in throughflow can induce transitions in the gap-leaping system when near a critical state (leaping-to-penetrating/ penetrating-to-leaping). Results from the study are interpreted within a nonlinear dynamical framework and various properties of the system are explored.

scholarly journals A Laboratory Study of Nonlinear Western Boundary Currents, with Application to the Gulf Stream Separation due to Inertial Overshooting*

2011 ◽  
Vol 41 (11) ◽  
pp. 2063-2079 ◽  
Author(s):  
Stefano Pierini ◽  
Pierpaolo Falco ◽  
Giovanni Zambardino ◽  
Thomas A. McClimans ◽  
Ingrid Ellingsen
Keyword(s):  
Gulf Stream ◽  
Functional Dependence ◽  
Western Boundary ◽  
Western Boundary Currents ◽  
Weakly Nonlinear ◽  
Boundary Currents ◽  
First Case ◽  
Highly Nonlinear ◽  
Cape Hatteras ◽  
Small Change

Abstract Various dynamical aspects of nonlinear western boundary currents (WBCs) have been investigated experimentally through physical modeling in a 5-m-diameter rotating basin. The motion of a piston with a velocity up that can be as low as up = 0.5 mm s−1 induces a horizontally unsheared current of homogeneous water that, flowing over a topographic beta slope, experiences westward intensification. First, the character of WBCs for various degrees of nonlinearity is investigated. By varying up, flows ranging from the highly nonlinear inertial Charney regime down to a weakly nonlinear regime can be simulated. In the first case, the dependence of zonal length scales on up is found to be in agreement with Charney’s theory; for weaker flows, a markedly different functional dependence emerges describing the initial transition toward the linear, viscous case. This provides an unprecedented coverage of nonlinear WBC dependence on an amplitude parameter in terms of experimental data. WBC separation from a wedge-shaped continent past a cape (simulating Cape Hatteras) due to inertial overshooting is then analyzed. By increasing current speed, a critical behavior is identified according to which a very small change of up marks the transition from a WBC that follows the coast past the cape to a WBC (nearly dynamically similar to a full-scale Gulf Stream) that separates from the cape without any substantial deflection, as with the Gulf Stream Extension. The important effect of the deflection angle of the continent is analyzed as well. Finally, the qualitative effect of a sloping sidewall along a straight coast is considered: the deflection of the flow away from the western wall due to the tendency to preserve potential vorticity clearly emerges.

scholarly journals Subtropical Western Boundary Currents over Slopes Detaching from Coasts with Inshore Pool Regions: An Indication to the Kuroshio Nearshore Path

2012 ◽  
Vol 42 (2) ◽  
pp. 306-320 ◽  
Author(s):  
Hajime Nishigaki ◽  
Humio Mitsudera
Keyword(s):  
Bottom Layer ◽  
Volume Transport ◽  
Western Boundary ◽  
Bottom Slope ◽  
Boundary Current ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
Layer Velocity ◽  
The Kuroshio ◽  
Upper Boundary

Abstract The dynamics of subtropical western boundary currents over slopes detaching from coasts with inshore pool regions, where the water of the subtropical gyre does not enter and the velocity is small, are investigated. This study is intended to understand the dynamics of the nearshore path of the Kuroshio, which has a distinct boundary between the boundary current and the coastal water. Numerical experiments under idealized conditions are made. The results show flow patterns with pool regions similar to the Kuroshio under simple conditions. A deep countercurrent is present on the lower bottom slope, which represents observed deep currents. This is part of a deep cyclonic recirculation north of the jet, which extends to the lower bottom slope despite steep topography. This extension can be explained by the geostrophic contours. In this region, the upper boundary current feels the bottom slope and the westward intensification is blocked. In the other region, where the bottom-layer velocity is very small, the upper boundary current is free from the bottom slope and westward intensification occurs at the coast. The sensitivity to the volume transport of the boundary current is investigated by case studies. The pool regions are broken in cases with large volume transports. It is indicated that these unsteady inshore regions are produced by instability caused by an outcrop of the upper isopycnal, which is led by a large baroclinic volume transport.

scholarly journals North Atlantic Western Boundary Currents Are Intense Dissolved Organic Carbon Streams

2020 ◽  
Vol 7 ◽  
Author(s):  
Marcos Fontela ◽  
Fiz F. Pérez ◽  
Herlé Mercier ◽  
Pascale Lherminier
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
North Atlantic ◽  
Gulf Stream ◽  
Western Boundary ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
The North ◽  
The North Atlantic

In the North Atlantic, there are two main western boundary currents related to the Atlantic Meridional Overturning Circulation (AMOC): the Gulf Stream flowing northward and the Deep Western Boundary Current (DWBC) flowing southward. Here we analyze data from the OVIDE section (GO-SHIP A25 Portugal-Greenland 40–60°N) that crosses the DWBC and the northward extension of the Gulf Stream, the North Atlantic Current. We show that North Atlantic western boundary currents play a key role in the transport of dissolved organic matter, specifically dissolved organic carbon (DOC). Revisited transports and budgets of DOC with new available data identify the eastern Subpolar North Atlantic (eSPNA) as an important source of locally produced organic matter for the North Atlantic and a key region in the supply of bioavailable DOC to the deep ocean. The East Greenland Current, and its upstream source the East Reykjanes Ridge Current on the eastern flank of the mid-Atlantic ridge, are export pathways of bioavailable DOC toward subtropical latitudes. The fast overturning and subsequent remineralization of DOC produced in the autotrophic eSPNA explains up to 38% of the total oxygen consumption in the deep North Atlantic between the OVIDE section and 24°N. Carbon budgets that do not take into account this organic remineralization process overestimates the natural uptake of carbon dioxide (CO2) from the atmosphere by one third. The inclusion of DOC transports in regional carbon budgets reconciles the estimates of CO2 uptake in the North Atlantic between model and observations.

A novel masking technique to investigate atmosphere-ocean interaction over Western Boundary Currents

2020 ◽  
Author(s):  
Fumi Hayashi
Keyword(s):  
Gulf Stream ◽  
General Circulation ◽  
Circulation Model ◽  
Western Boundary ◽  
Atmospheric Response ◽  
Low Resolution ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
Oceanic Fronts ◽  
The Difference

<p>Western Boundary Currents (WBC), such as the Gulf Stream, leave a strong imprint on the ocean-atmosphere boundary in the form of strong gradients and high variability of Sea Surface Temperature (SST). Recent studies have shown that midlatitude oceanic fronts have an influence throughout the depth of the troposphere by means of synoptic systems such as weather fronts. An understanding of how the midlatitude ocean influences the synoptic system is crucial for better climate projection, however, this has been challenging. For example, in model simulations the sensitivity of the atmosphere to SST anomalies are dependent on its resolution, with low resolution models unable to capture the air-sea interactions occurring over warm sectors of midlatitude cyclones, possibly leading to underestimations of the oceanic influence on the atmosphere. A novel modelling technique is developed in which an interactive “mask” is used to systematically isolate and study the air-sea interaction over different synoptic regimes (warm and cold sector). Here, simulations using an idealised aqua-planet atmospheric general circulation model (AGCM) are used to study the atmospheric response to a tightening of SST gradient (comparable to that of the Gulf Stream) over the cold sector (“cold path”) and the warm sector (“warm path”) separately. Same experiments will also be performed on models with higher resolution to investigate the difference in atmospheric response between the high and low resolution models and what physical processes are responsible for such change in response.</p>

scholarly journals Bjerknes-like Compensation in the Wintertime North Pacific

2015 ◽  
Vol 45 (5) ◽  
pp. 1339-1355 ◽  
Author(s):  
Stuart P. Bishop ◽  
Frank O. Bryan ◽  
R. Justin Small
Keyword(s):  
North Pacific ◽  
Kuroshio Extension ◽  
Western Boundary ◽  
Meridional Heat Transport ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific ◽  
Kuroshio Extension Region

AbstractObservational and model evidence has been mounting that mesoscale eddies play an important role in air–sea interaction in the vicinity of western boundary currents and can affect the jet stream storm track. What is less clear is the interplay between oceanic and atmospheric meridional heat transport in the vicinity of western boundary currents. It is first shown that variability in the North Pacific, particularly in the Kuroshio Extension region, simulated by a high-resolution fully coupled version of the Community Earth System Model matches observations with similar mechanisms and phase relationships involved in the variability. The Pacific decadal oscillation (PDO) is correlated with sea surface height anomalies generated in the central Pacific that propagate west preceding Kuroshio Extension variability with a ~3–4-yr lag. It is then shown that there is a near compensation of O(0.1) PW (PW ≡ 1015 W) between wintertime atmospheric and oceanic meridional heat transport on decadal time scales in the North Pacific. This compensation has characteristics of Bjerknes compensation and is tied to the mesoscale eddy activity in the Kuroshio Extension region.

scholarly journals Radiating Instability of a Meridional Boundary Current

2008 ◽  
Vol 38 (10) ◽  
pp. 2294-2307 ◽  
Author(s):  
Hristina G. Hristova ◽  
Joseph Pedlosky ◽  
Michael A. Spall
Keyword(s):  
Western Boundary ◽  
Far Field ◽  
Boundary Current ◽  
Important Conclusion ◽  
Western Boundary Currents ◽  
Horizontal Structure ◽  
Boundary Currents ◽  
Zonal Jets ◽  
Eastern Boundary ◽  
Eastern Boundary Current

Abstract A linear stability analysis of a meridional boundary current on the beta plane is presented. The boundary current is idealized as a constant-speed meridional jet adjacent to a semi-infinite motionless far field. The far-field region can be situated either on the eastern or the western side of the jet, representing a western or an eastern boundary current, respectively. It is found that when unstable, the meridional boundary current generates temporally growing propagating waves that transport energy away from the locally unstable region toward the neutral far field. This is the so-called radiating instability and is found in both barotropic and two-layer baroclinic configurations. A second but important conclusion concerns the differences in the stability properties of eastern and western boundary currents. An eastern boundary current supports a greater number of radiating modes over a wider range of meridional wavenumbers. It generates waves with amplitude envelopes that decay slowly with distance from the current. The radiating waves tend to have an asymmetrical horizontal structure—they are much longer in the zonal direction than in the meridional, a consequence of which is that unstable eastern boundary currents, unlike western boundary currents, have the potential to act as a source of zonal jets for the interior of the ocean.

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