Purpose: Gulf of California: The California Undercurrent (CU) is a poorly-described eastern boundary countercurrent which originates in the eastern tropical Pacific (ETP) warm pool and flows northward along the continental slope and shelf of North America, transporting water and organisms to Monterey Bay and beyond. Off Monterey Bay the CU has maximum velocity near 10 cm/s at 100 but reaches to at least 1000 m (mean core velocity, 4.2 cm/s). Its waters are deficient in oxygen but may be enriched in iron. Off central California the CU is typically weak and subsurface during the first half of the year but strengthens and shoals during the latter half of the year. Because the CU provides source waters for coastal upwelling, its biogeochemistry and chemical evolution has significant consequences for the overall biological productivity of the California Current System. The Western Flyer transit south to the Gulf of California (GOCSB 2012) provides an ideal vehicle for tracing the evolution these waters as they flow from the ETP to central California. We propose to make CTD and underway measurements from Monterey Bay to a pCO2 mooring off Manzanillo, time permitting. This transit will occur during late winter. As time permits we will continue to occupy stations south, past Cabo San Lucas, and into the ETP. This section will be a repeat of a similar one made almost 10 years prior in 2003. Since then the concentration of oxygen has decreased and the concentration of inorganic carbon has increased systematically. This repeat cruise will allow us to document these changes over large spatial scales and is the primary focus of this expedition. We will describe the hydrography, nutrient chemistry, and phytoplankton of the CU and overlying waters. We will trace the CU along a >1000 mile length of coast off western North America, providing descriptions of (1) chemical development of upwelling source waters as they flow north from the ETP, and (2) alongshore chemical and biological variability in coastal upwelling ecosystems. Results will be disseminated through posters, lectures, and publications.
Chief scientist: Francisco Chavez
Scheduled start time: 2/4/2012 3:00:00 PM UTC
[2/4/2012 7:00:00 AM Pacific]
Scheduled end time: 2/14/2012 12:30:00 AM UTC
[2/13/2012 4:30:00 PM Pacific]
Equipment: Sampling will be based on 1000 m near-bottom CTD casts. At all stations a CTD cast will be made to near the bottom at 1000 m. At mid-day stations optics (HyperPro) casts will be made by hand. Underway measurements will be made for the full duration of both legs, and include CTD, fish finder, ADCP, pCO2 (Friederich), FRRF (Chavez), etc. CTD rosette Optical profiler (Hyperpro) Underway CTD Fast Repetition Rate Fluorometer Underway pCO2 (Friederich) pH