Inner Shelf Diurnal Temperature Variability Hot Spot

Matt Gough1, Jamie MacMahan2, Michael Kovatch3, Falk Feddersen4, John Colosi1, Jack A Barth5, James A Lerczak6, Amy Frances Waterhouse7, Jennifer A MacKinnon8 and Joe Calantoni9, (1)Naval Postgraduate School, Monterey, CA, United States, (2)Naval Postgraduate School, Oceanography, Monterey, United States, (3)Scripps Institution of Oceanography, La Jolla, CA, United States, (4)University of California San Diego, Scripps Institution of Oceanography, La Jolla, United States, (5)Oregon State University, Marine Studies Initiative, Corvallis, OR, United States, (6)Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, OR, United States, (7)Scripps Institution of Oceanography, La Jolla, United States, (8)UC San Diego, Scripps Institution of Oceanography, La Jolla, United States, (9)U.S. Naval Research Laboratory, Stennis Space Center, DC, United States
Abstract:
Measures of temperature over the vertical were obtained at 93 moorings located along a 60 km stretch of coastline in central California at water depths d = 100 m to 9 m between August-October 2017 as part of the ONR Inner Shelf DRI. The coastline is interrupted by three coastal promontories: Pt. San Luis, Pt. Sal, and Pt. Purisima. Vertical and spatial diurnal temperature (TDU(z) and TDU(x,y)) variability are investigated by employing empirical orthogonal analysis (EOF) techniques on diurnal band-passed temperature observations. The TDU mode 1 vertical EOF (φDU(z)1) accounted for more than 65% of the TDU(z) variability at 86 of the moorings and averaged 81%. The remaining 7 moorings, which account for less than 65% of the TDU(z) variability, are discarded from further analysis. Three primary patterns in the φDU(z)1 profiles are exhibited: A baroclinic pattern with middle water column TDU(z) variance maxima which occurred at moorings in d > 20m, a nearly depth-uniform TDU(z) variance pattern which occurred at moorings in d < 20m, and surface TDU(z) variance maxima which typically occurred south of coastal promontories. For spatial complex EOF analyses performed on moorings with nearly depth uniform φDU(z)1, the mode 1 diurnal spatial complex EOF (φDU(x,y)1) accounts for 80% of the total TDU(x,y) variability, and exhibits an equatorward TDU(z) signal propagation ranging between 1-2 m/s that initiates south of coastal promontories. For spatial complex EOF analyses performed on moorings with a baroclinic φDU(z)1 profile, the φDU(x,y)1 accounts for 75% of the total TDU(x,y) variability. The φDU(x,y)1 also reveals a hot spot in TDU(x,y) variability that occurs directly north of Pt. Sal where the magnitude of φDU(x,y)1 increases. Additionally, the TDU(x,y) signal propagates towards this hot spot from all directions.
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