|Title||Annual and interannual variability in the California Current System: Comparison of an ocean state estimate with a network of underwater gliders|
|Publication Type||Journal Article|
|Year of Publication||2018|
|Authors||Zaba K, Rudnick DL, Cornuelle B, Gopalakrishnan G, Mazloff M|
|Journal||Journal of Physical Oceanography|
A data-constrained state estimate of the southern California Current System (CCS) is presented and compared against withheld CalCOFI data and assimilated glider data over the years 2007-2017. 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/m3 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 in late summer to early fall and of isopycnal heave due to 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 2014-2016 and a positive isopycnal salinity anomaly that peaked with the 2015-2016 El Niño.