Across-shore Propagation of Subthermocline Eddies in the California Current System

2021 ◽  
Keyword(s):  
Wave Speed ◽  
High Salinity ◽  
Current System ◽  
California Current ◽  
Propagation Speed ◽  
Underwater Glider ◽  
Salt Balance ◽  
Sea Level Anomaly ◽  
California Current System ◽  
Baroclinic Rossby Wave

AbstractThough subthermocline eddies (STEs) have often been observed in the world oceans, characteristics of STEs such as their patterns of generation and propagation are less understood. Here, the across-shore propagation of STEs in the California Current System (CCS) is observed and described using 13 years of sustained coastal glider measurements on three glider transect lines off central and southern California as part of the California Underwater Glider Network (CUGN). The across-shore propagation speed of anticyclonic STEs is estimated as 1.35-1.49 ± 0.33 cm s−1 over the three transects, Line 66.7, Line 80.0, and Line 90.0, close to the westward long first baroclinic Rossby wave speed in the region. Anticyclonic STEs are found with high salinity, high temperature, and low dissolved oxygen anomalies in their cores, consistent with transporting California Undercurrent water from the coast to offshore. Comparisons to satellite sea-level anomaly indicate that STEs are only weakly correlated to a sea surface height expression. The observations suggest that STEs are important for the salt balance and mixing of water masses across-shore in the CCS.

scholarly journals Spray Underwater Glider Operations

2016 ◽  
Vol 33 (6) ◽  
pp. 1113-1122 ◽  
Author(s):  
Daniel L. Rudnick ◽  
Russ E. Davis ◽  
Jeffrey T. Sherman
Keyword(s):  
Survival Analysis ◽  
Current System ◽  
California Current ◽  
Horizontal Resolution ◽  
Underwater Glider ◽  
California Current System ◽  
Boundary Currents ◽  
Small Vessels ◽  
Underwater Gliders ◽  
Mission Duration

AbstractOperational statistics for the Spray underwater glider are presented to demonstrate capabilities for sustained observations. An underwater glider is an autonomous device that profiles vertically by changing buoyancy and flies horizontally on wings. The focus has been on sustained observations of boundary currents to take advantage of the glider’s small size, which allows it to be deployed and recovered from small vessels close to land, and the fine horizontal resolution delivered by the glider, which is scientifically desirable in boundary regions. Since 2004, Spray underwater gliders have been deployed for over 28 000 days, traveling over 560 000 km, and delivering over 190 000 profiles. More than 10 gliders, on average, have been in the water since 2012. Statistics are given in the form of histograms for 297 completed glider missions of longer than 5 days. The statistics include mission duration, number of dives, distance over ground, and horizontal and vertical distance through water. A discussion of problems, losses, and short missions includes a survival analysis. The most extensive work was conducted in the California Current system, where observations on three across-shorelines have been sustained, with 97% coverage since 2009. While the authors have certain advantages as developers and builders of the Spray underwater glider and Spray may have design and construction advantages, they believe these statistics are a sound basis for optimism about the widespread future of gliders in oceanographic observing.

scholarly journals Reconstruction of Diffusion Coefficients and Power Exponents from Single Lagrangian Trajectories

Fluids ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 111
Author(s):  
Leonid M. Ivanov ◽  
Collins A. Collins ◽  
Tetyana Margolina
Keyword(s):  
Black Sea ◽  
Diffusion Coefficients ◽  
Current System ◽  
Mean Square Displacement ◽  
California Current ◽  
The Black Sea ◽  
Mean Square ◽  
California Current System ◽  
The Mean ◽  
Non Gaussian

Using discrete wavelets, a novel technique is developed to estimate turbulent diffusion coefficients and power exponents from single Lagrangian particle trajectories. The technique differs from the classical approach (Davis (1991)’s technique) because averaging over a statistical ensemble of the mean square displacement (<X2>) is replaced by averaging along a single Lagrangian trajectory X(t) = {X(t), Y(t)}. Metzler et al. (2014) have demonstrated that for an ergodic (for example, normal diffusion) flow, the mean square displacement is <X2> = limT→∞τX2(T,s), where τX2 (T, s) = 1/(T − s) ∫0T−s(X(t+Δt) − X(t))2 dt, T and s are observational and lag times but for weak non-ergodic (such as super-diffusion and sub-diffusion) flows <X2> = limT→∞≪τX2(T,s)≫, where ≪…≫ is some additional averaging. Numerical calculations for surface drifters in the Black Sea and isobaric RAFOS floats deployed at mid depths in the California Current system demonstrated that the reconstructed diffusion coefficients were smaller than those calculated by Davis (1991)’s technique. This difference is caused by the choice of the Lagrangian mean. The technique proposed here is applied to the analysis of Lagrangian motions in the Black Sea (horizontal diffusion coefficients varied from 105 to 106 cm2/s) and for the sub-diffusion of two RAFOS floats in the California Current system where power exponents varied from 0.65 to 0.72. RAFOS float motions were found to be strongly non-ergodic and non-Gaussian.

scholarly journals Persistent spatial structuring of coastal ocean acidification in the California Current System

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
F. Chan ◽  
J. A. Barth ◽  
C. A. Blanchette ◽  
R. H. Byrne ◽  
F. Chavez ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Current System ◽  
California Current ◽  
Coastal Ocean ◽  
California Current System ◽  
Spatial Structuring

scholarly journals Surface Stress and Atmospheric Boundary Layer Response to Mesoscale SST Structure in Coupled Simulations of the Northern California Current System

2019 ◽  
Vol 148 (1) ◽  
pp. 259-287
Author(s):  
R. M. Samelson ◽  
L. W. O’Neill ◽  
D. B. Chelton ◽  
E. D. Skyllingstad ◽  
P. L. Barbour ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Stress ◽  
Current System ◽  
California Current ◽  
Heat Fluxes ◽  
Neutral Stability ◽  
Northern California ◽  
Coupling Coefficients ◽  
California Current System ◽  
Northern California Current

Abstract The influence of mesoscale sea surface temperature (SST) variations on wind stress and boundary layer winds is examined from coupled ocean–atmosphere numerical simulations and satellite observations of the northern California Current System. Model coupling coefficients relating the divergence and curl of wind stress and wind to downwind and crosswind SST gradients are generally smaller than observed values and vary by a factor of 2 depending on planetary boundary layer (PBL) scheme, with values larger for smoothed fields on the 0.25° observational grid than for unsmoothed fields on the 12-km model grid. Divergence coefficients are larger than curl coefficients on the 0.25° grid but not on the model grid, consistent with stronger scale dependence for the divergence response than for curl in a spatial cross-spectral analysis. Coupling coefficients for 10-m equivalent neutral stability winds are 30%–50% larger than those for 10-m wind, implying a correlated effect of surface-layer stability variations. Crosswind surface air temperature and SST gradients are more strongly coupled than downwind gradients, while the opposite is true for downwind and crosswind heat flux and SST gradients. Midlevel boundary layer wind coupling coefficients show a reversed response relative to the surface that is predicted by an analytical model; a predicted second reversal with height is not seen in the simulations. The relative values of coupling coefficients are consistent with previous results for the same PBL schemes in the Agulhas Return Current region, but their magnitudes are smaller, likely because of the effect of mean wind on perturbation heat fluxes.

scholarly journals Remote forcing of subsurface currents and temperatures near the northern limit of the California Current System

2016 ◽  
Vol 121 (10) ◽  
pp. 7244-7262 ◽  
Author(s):  
Zelalem Engida ◽  
Adam Monahan ◽  
Debby Ianson ◽  
Richard E. Thomson
Keyword(s):  
Current System ◽  
California Current ◽  
Northern Limit ◽  
California Current System ◽  
Remote Forcing
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