Pilot Modeling, Summer 2000

1. Pilot simulation – Year 2000 Summer Period

The nested COAWST setup was configured to hindcast the period of June-July 2000. In planning the PSIEX pilot field program, many animations were created from these model results. These were the basis of many discussions between modeling and observational groups to identify interesting regions, flow features, and sampling strategies. The animations can be viewed at our Youtube Pt. Sal playlist. 

The output from this simulation was used to conduct a study on wind relaxation and a coastal buoyant plume north of Pt. Conception. During summer, under persistent upwelling-favorable winds, large thermal gradients develop between the shelf adjacent to the Santa Maria Basin and the Santa Barbara Channel (Figure 1). The modeled period simulates these conditions.

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Figure 1. Sea surface temperature (SST) snapshot on 11 June 2000 observed by the Advanced Very High Resolution Radiometer (AVHRR). Regional locations are labeled; Santa Maria Basin (SMB), Southern California Bight (SCB), Santa Barbara Channel (SBC), Pt. Sal and Pt. Conception. The dashed black–white contour is the 200 m isobath, denoting the continental shelf.

 

 

 

 

 

 

When upwelling-favorable winds relax, warm water within the Santa Barbara Channel flows northward as a buoyant plume similar to a river entering the coastal ocean (Figure 2).

 

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Figure 2. Three snapshots of modeled (a – c) SST and (d – f) cross-shore and vertical temperature transects at latitude of Pt. Purisma mooring (34.73oN, white dashed line in a – c). Bathymetry contours are in 50 m intervals, and the 15oC and 17oC isotherms are contoured black.

 

 

 

 

 

 

 

 

 

Model results compare well with historical moored datasets courtesy of the Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO) and the Minerals Management Service Santa Maria Basin-Santa Barbara Channel study (Figure 3). The base of the plume is approximately 30-m deep and impacts the entire inner-shelf water column. On the mid- and outer-shelves, the plume is a surface-trapped feature with little signature at depth.

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Figure 3. Observed (a) and modeled (b) temperature time series from three depths at the Pt. Purisma (PUR) mooring in 15-m water depth. The 5oC temperature increase associated with the arrival of SBC water extends throughout the water column.

 

 

 

 

 

 

 

 

This work was recently published in JGR Oceans. Please see link for more details:

Suanda, S.H., Kumar, N., Miller, A.J., Di Lorenzo, E., Haas, K., Cai, D., Edwards, C.A., Washburn, L., Fewings, M.R., Torres, R., Feddersen, F., 2016. Wind relaxation and a coastal buoyant plume north of Pt. Conception, CA: Observations, simulations, and scalings. J. Geophys. Res. Oceans 121, 7455–7475. doi:10.1002/2016JC011919 – [ online article ]