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Seasonal and interannual variability in along‐slope oceanic properties off the US W est C oast: Inferences from a high‐resolution regional model
Author(s) -
Kurapov A. L.,
Pelland N. A.,
Rudnick D. L.
Publication year - 2017
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2017jc012721
Subject(s) - downwelling , isopycnal , upwelling , geology , oceanography , annual cycle , climatology , seasonality , continental shelf , ocean current , boundary current , current (fluid) , statistics , mathematics
A 6 year, 2009–2014 simulation using a 2 km horizontal resolution ocean circulation model of the Northeast Pacific coast is analyzed with focus on seasonal and interannual variability in along‐slope subsurface oceanic properties. Specifically, the fields are sampled on the isopycnal surface σ = 26 . 5 kg m −3 that is found between depths of 150 and 300 m below the ocean surface over the continental slope. The fields analyzed include the depthz 26 . 5, temperatureT 26 . 5, along‐slope currentv 26 . 5, and the average potential vorticity PV between σ = 26.5 and 26.25 kg m −3 . Each field is averaged in the cross‐shore direction over the continental slope and presented as a function of the alongshore coordinate and time. The seasonal cycle inz 26 . 5shows a coherent upwelling‐downwelling pattern from Mexico to Canada propagating to the north with a speed of 0.5 m s −1 . The anomalously deep ( − 20 m)z 26 . 5displacement in spring‐summer 2014 is forced by the southern boundary condition at 24°N as a manifestation of an emerging strong El Niño. The seasonal cycle inT 26 . 5is most pronounced between 36°N and 53°N indicating that subarctic waters are replaced by warmer Californian waters in summer with the speed close 0.15 m s −1 , which is consistent with earlier estimates of the undercurrent speed and also presentv 26 . 5analyses. The seasonal patterns and anomalies inz 26 . 5andT 26 . 5find confirmation in available long‐term glider and shipborne observations. The PV seasonality over the slope is qualitatively different to the south and north of the southern edge of Heceta Bank (43.9°N).