A climatology of the California Current System from a network of underwater gliders

TitleA climatology of the California Current System from a network of underwater gliders
Publication TypeJournal Article
Year of Publication2017
AuthorsRudnick D.L, Zaba K.D, Todd R.E, Davis R.E
JournalProgress in Oceanography
Date Published2017/05
Type of ArticleArticle
ISBN Number0079-6611
Accession NumberWOS:000403135500005
Keywordscalifornia current system; Climatology; cycle; el-nino; flow patterns; ocean climatology; pacific; salinity; seasonal variability; temperature; total geostrophic circulation; tracers; transports; underwater gliders; velocity

Autonomous underwater gliders offer the possibility of sustained observation of the coastal ocean. Since 2006 Spray underwater gliders in the California Underwater Glider Network (CUGN) have surveyed along California Cooperative Oceanic Fisheries Investigations (CalCOFI) lines 66.7, 80.0, and 90.0, constituting the world's longest sustained glider network, to our knowledge. In this network, gliders dive between the surface and 500 m, completing a cycle in 3 h and covering 3 km in that time. Sections extend 350500 km offshore and take 2-3 weeks to occupy. Measured variables include pressure, temperature, salinity, and depth-average velocity. The CUGN has amassed over 10,000 glider-days, covering over 210,000 km with over 95,000 dives. These data are used to produce a climatology whose products are for each variable a mean field, an annual cycle, and the anomaly from the annual cycle. The analysis includes a weighted least-squares fit to derive the mean and annual cycle, and an objective map to produce the anomaly. The final results are variables on rectangular grids in depth, distance offshore, and time. The mean fields are finely resolved sections across the main flows in the California Current System, including the poleward California Undercurrent and the equatorward California Current. The annual cycle shows a phase change from the surface to the thermocline, reflecting the effects of air/sea fluxes at the surface and upwelling in the thermocline. The interannual anomalies are examined with an emphasis on climate events of the last ten years including the 2009-2010 El Nino, the 2010-2011 La Nina, the warm anomaly of 2014-2015, and the 2015-2016 El Nino. (C) 2017 Elsevier Ltd. All rights reserved.

Short TitleProg. Oceanogr.

Our intention with this work has been to produce a climatology for study of the regional effects on the southern CCS of interannual climate variability. Calculating the mean and annual cycle is an essential step towards the interannual anomalies, and these results have their own value. We hope this climatology will prove useful to anyone interested in the CCS, whether to examine the physical processes quantified by these observations of temperature, salinity and velocity, or to place in context other measurements in the region. For example, we are using the climatology to quantify the mass, heat, and salt budgets during the 2014–2015 warm anomaly and 2015–2016 El Niño (Zaba and Rudnick, unpublished manuscript). We also expect that the climatology will prove useful for validation of regional models of ocean circulation.

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