Application of a data-assimilative regional ocean modeling system for assessing California Current System ocean conditions, krill, and juvenile rockfish interannual variability

2014 ◽  
Vol 41 (16) ◽  
pp. 5942-5950 ◽  
Author(s):  
Isaac D. Schroeder ◽  
Jarrod A. Santora ◽  
Andrew M. Moore ◽  
Christopher A. Edwards ◽  
Jerome Fiechter ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Current System ◽  
California Current ◽  
Ocean Modeling ◽  
Regional Ocean Modeling System ◽  
California Current System ◽  
Ocean Conditions

scholarly journals Permanent Meanders in the California Current System

2008 ◽  
Vol 38 (8) ◽  
pp. 1690-1710 ◽  
Author(s):  
L. R. Centurioni ◽  
J. C. Ohlmann ◽  
P. P. Niiler
Keyword(s):  
Sea Level ◽  
Current System ◽  
California Current ◽  
Ocean Model ◽  
Ocean Modeling ◽  
Surface Velocity ◽  
Regional Ocean Modeling System ◽  
Near Surface ◽  
Geostrophic Velocity ◽  
California Current System

Abstract Surface Velocity Program (SVP) drifter data from 1987 through 2005; Archiving, Validation, and Interpretation of Satellite Oceanographic data (AVISO) sea level anomalies; and NCEP reanalysis winds are used to assemble a time-averaged map of the 15-m-deep geostrophic velocity field in the California Current System seaward of about 50 km from the coast. The wind data are used to compute the Ekman currents, which are then subtracted from the drifter velocity measurements. The resulting proxy for geostrophic velocity anomalies computed from drifters and from satellite sea level measurements are combined to form an unbiased mean geostrophic circulation map. The result shows a California Current System that flows southward with four permanent meanders that can extend seaward for more than 800 km. Bands of alternating eastward and westward zonal currents are connected to the meanders and extend several thousand kilometers into the Pacific Ocean. This observed time-mean circulation and its associated eddy energy are compared to those produced by various high-resolution OGCM solutions: Regional Ocean Modeling System (ROMS; 5 km), Parallel Ocean Program model (POP; 1/10°), Hybrid Coordinate Ocean Model (HYCOM; 1/12°), and Naval Research Laboratory (NRL) Layered Ocean Model (NLOM; 1/32°). Simulations in closest agreement with observations come from ROMS, which also produces four meanders, geostrophic time-mean currents, and geostrophic eddy energy consistent with the observed values. The time-mean ageostrophic velocity in ROMS is strongest within the cyclonic part of the meanders and is similar to the ageostrophic velocity produced by nonlinear interaction of Ekman currents with the near-surface vorticity field.

Interannual variability in bottom-up processes in the upstream range of the California Current system: An isotopic approach

2012 ◽  
Vol 106 ◽  
pp. 16-27 ◽  
Author(s):  
Rana W. El-Sabaawi ◽  
Marc Trudel ◽  
David L. Mackas ◽  
John F. Dower ◽  
Asit Mazumder
Keyword(s):  
Interannual Variability ◽  
Current System ◽  
California Current ◽  
Bottom Up ◽  
California Current System

scholarly journals Annual and Interannual Variability in the California Current System: Comparison of an Ocean State Estimate with a Network of Underwater Gliders

2018 ◽  
Vol 48 (12) ◽  
pp. 2965-2988 ◽  
Author(s):  
Katherine D. Zaba ◽  
Daniel L. Rudnick ◽  
Bruce D. Cornuelle ◽  
Ganesh Gopalakrishnan ◽  
Matthew R. Mazloff
Keyword(s):  
Interannual Variability ◽  
Large Scale ◽  
Current System ◽  
Potential Temperature ◽  
California Current ◽  
Late Summer ◽  
Near Surface ◽  
State Estimate ◽  
California Current System ◽  
Annual Cycles

AbstractA data-constrained state estimate of the southern California Current System (CCS) is presented and compared with withheld California Cooperative Oceanic Fisheries Investigations (CalCOFI) data and assimilated glider data over 2007–17. The objective of this comparison is to assess the ability of the California State Estimate (CASE) to reproduce the key physical features of the CCS mean state, annual cycles, and interannual variability along the three sections of the California Underwater Glider Network (CUGN). The assessment focuses on several oceanic metrics deemed most important for characterizing physical variability in the CCS: 50-m potential temperature, 80-m salinity, and 26 kg m−3 isopycnal depth and salinity. In the time mean, the CASE reproduces large-scale thermohaline and circulation structures, including observed temperature gradients, shoaling isopycnals, and the locations and magnitudes of the equatorward California Current and poleward California Undercurrent. With respect to the annual cycle, the CASE captures the phase and, to a lesser extent, the magnitude of upper-ocean warming and stratification from late summer to early fall and of isopycnal heave during springtime upwelling. The CASE also realistically captures near-surface diapycnal mixing during upwelling season and the semiannual cycle of the California Undercurrent. In terms of interannual variability, the most pronounced signals are the persistent warming and downwelling anomalies of 2014–16 and a positive isopycnal salinity anomaly that peaked with the 2015–16 El Niño.

An Adjoint Sensitivity Analysis of the Southern California Current Circulation and Ecosystem

2009 ◽  
Vol 39 (3) ◽  
pp. 702-720 ◽  
Author(s):  
Andrew M. Moore ◽  
Hernan G. Arango ◽  
Emanuele Di Lorenzo ◽  
Arthur J. Miller ◽  
Bruce D. Cornuelle
Keyword(s):  
Sensitivity Analysis ◽  
Kinetic Energy ◽  
Wind Stress ◽  
Current System ◽  
Baroclinic Instability ◽  
California Current ◽  
Eddy Kinetic Energy ◽  
Ocean Modeling ◽  
Complex Flow ◽  
California Current System

Abstract Adjoint methods of sensitivity analysis were applied to the California Current using the Regional Ocean Modeling Systems (ROMS) with medium resolution, aimed at diagnosing the circulation sensitivity to variations in surface forcing. The sensitivities of coastal variations in SST, eddy kinetic energy, and baroclinic instability of complex time-evolving flows were quantified. Each aspect of the circulation exhibits significant interannual and seasonal variations in sensitivity controlled by mesoscale circulation features. Central California SST is equally sensitive to wind stress and surface heat flux, but less so to wind stress curl, displaying the greatest sensitivity when upwelling-favorable winds are relaxing and the least sensitivity during the peak of upwelling. SST sensitivity is typically 2–4 times larger during summer than during spring, although larger variations occur during some years. The sensitivity of central coast eddy kinetic energy to surface forcing is constant on average throughout the year. Perturbations in the wind that align with mesoscale eddies to enhance the strength of the circulation by local Ekman pumping yield the greatest sensitivities. The sensitivity of the potential for baroclinic instability is greatest when nearshore horizontal temperature gradients are largest, and it is associated with variations in wind stress concentrated along the core of the California Current. The sensitivity varies by a factor of ∼1.5 throughout the year. A new and important aspect of this work is identification of the complex flow dependence and seasonal dependence of the sensitivity of the ROMS California Current System (CCS) circulation to variations in surface forcing that was hitherto not previously appreciated.

scholarly journals What controls biological productivity in coastal upwelling systems? Insights from a comparative modeling study

2011 ◽  
Vol 8 (3) ◽  
pp. 5617-5652 ◽  
Author(s):  
Z. Lachkar ◽  
N. Gruber
Keyword(s):  
Coastal Upwelling ◽  
Current System ◽  
Nutrient Recycling ◽  
Comparative Modeling ◽  
Ocean Modeling ◽  
Residence Times ◽  
Biological Productivity ◽  
Regional Ocean Modeling System ◽  
California Current System ◽  
Modeling Study

Abstract. The magnitude of the biological productivity in Eastern Boundary Upwelling Systems (EBUS) is traditionally viewed as directly reflecting the upwelling intensity. Yet, different EBUS show different sensitivities of productivity to upwelling-favorable winds (Carr and Kearns, 2003). Here, using a comparative modeling study of the California Current System (California CS) and Canary Current System (Canary CS), we show how physical and environmental factors, such as light, temperature and cross-shore circulation modulate the response of biological productivity to upwelling strength. To this end, we made a series of eddy-resolving simulations of the California CS and Canary CS using the Regional Ocean Modeling System (ROMS), coupled to a nitrogen based Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) ecosystem model. We find the nutrient content of the euphotic zone to be 20 % smaller in the Canary CS relative to the California CS. Yet, the biological productivity is 50 % smaller in the latter. This is due to: (1) a faster nutrient-replete growth in the Canary CS relative to the California CS, related to a more favorable light and temperature conditions in the Canary CS, and (2) the longer nearshore water residence times in the Canary CS which lead to larger buildup of biomass in the upwelling zone, thereby enhancing the productivity. The longer residence times in the Canary CS appear to be associated with the wider continental shelves and the lower eddy activity characterizing this upwelling system. This results in a weaker offshore export of nutrients and organic matter, thereby increasing local nutrient recycling and enhancing the coupling between new and export production in the Northwest African system. Our results suggest that climate change induced perturbations such as upwelling favorable wind intensification might lead to contrasting biological responses in the California CS and the Canary CS, with major implications for the biogeochemical cycles and fisheries in these two ecosystems.

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