Suanda, S., N. Kumar, A. J. Miller, E.
Di Lorenzo, K. Haas, D. Cai, C. A. Edwards, L.
Washburn, M. Fewings, R. Torres and F. Feddersen, 2016:
Wind relaxation and a coastal buoyant plume north
of Pt. Conception, CA: Observations, simulations,
and scalings
Journal of Geophysical Research-Oceans, 121,
7455-7475.
Abstract.
In upwelling regions, wind relaxations lead to poleward
propagating warm water plumes that are important to coastal ecosystems. The
coastal ocean response to wind relaxation around Pt. Conception, CA is
simulated with a Regional Ocean Model (ROMS) forced by realistic surface and
lateral boundary conditions including tidal processes. The model reproduces
well the statistics of observed subtidal water column temperature and
velocity at both outer- and inner-shelf mooring locations throughout the study.
A poleward-propagating plume of Southern California Bight water that
increases shelf water temperatures by ~5C is also reproduced. Modeled plume
propagation speed, spatial scales, and
flow structure are consistent with a
theoretical scaling for coastal buoyant plumes with both surface-trapped and
slope-controlled dynamics. Plume momentum balances are distinct between
the offshore (> 30-m depth) region where the plume is surface-trapped, and
onshore of the 30-m isobath (within 5 km from shore) where the plume
water mass extends to the bottom and is slope-controlled. In the onshore
region, bottom stress is important in the alongshore momentum equation and
generates vertical vorticity that is an order of magnitude larger than the
vorticity in the plume core. Numerical experiments without tidal forcing show
that modeled surface temperatures are biased 0.5C high, potentially
affecting plume propagation distance and persistence.
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