Recurrent frontal slicks of a coastal ocean upwelling shadow

Abstract

[1] Marine ecosystems are greatly influenced by the structure and dynamics of fronts. In coastal upwelling systems, frontogenesis occurs frequently by upwelling and transport of cold water and warming in sheltered "upwelling shadow" retention sites. Monterey Bay, in the California Current upwelling system, hosts a dynamic upwelling shadow environment. Using a decade of satellite synthetic aperture radar (SAR) observations with ancillary remote sensing and in situ data, we describe recurrent surface slicks that develop along the seaward periphery of the Monterey Bay upwelling shadow, and we examine their relationships with fronts. Slick median dimensions, 17.5 km long and 0.8 km wide, describe their elongated structure. Although the typical pattern is a single slick, multiple slicks may concurrently develop in association with different types of fronts. Repeated volume surveys through a front, underlying a slick, revealed lateral mixing and interleaving of regional water types. Velocity fields from coastal HF radar show that slicks may coincide with a variety of surface circulation patterns, that they may extend contiguously across regions having very different surface velocity, and that they may be separated from the shear front of upwelling filaments by 5-10 km. Slicks occur in all seasons and may coincide with both upwelling and downwelling wind forcing. Surfactant accumulation in small-scale convergence zones is indicated as the primary mechanism of slick formation, not ocean current shear or small-scale air-sea coupling. The results of this study emphasize the role of upwelling system fronts in creating small-scale structure and dynamics that influence plankton ecology.

Application of the Hyperspectral Imager for the Coastal Ocean to Phytoplankton Ecology Studies in Monterey Bay, CA, USA

“…To examine regional sea surface temperature (SST) patterns, we used data from the Advanced Very High Resolution Radiometer (AVHRR) constellation of sensors. The AVHRR processing methods applied in this study are documented elsewhere [25].…”

Shoreward swimming boosts modeled nearshore larval supply and pelagic connectivity in a coastal upwelling region

“…Fronts are associated with phytoplankton blooms and aggregate phytoplankton and larvae, and these phenomena are well-documented in central California (Bjorkstedt et al, 2002;Graham et al, 1992;Ryan et al, 2010Ryan et al, , 2014Traganza and Conrad, 1981;Woodson et al, 2009). Fronts are common and persistent in the CCS (Castelao et al, 2006;Shanks et al, 2003a), and are spatially correlated with higher recruitment of both intertidal and subtidal species .…”

Plankton distribution and ocean dispersal

“…Results from two decades of research reveal that thin plankton layers are a crucial component of marine ecosystem dynamics. Far from being unusual or rare, thin layers of plankton are common features and can be found in a wide variety of environments (Bjornsen and Nielsen, 1991;Donaghay et al, 1992;Cowles and Desiderio, 1993;Dekshenieks et al, 2001;Cowles, 2003;McManus et al, 2003;McManus et al, 2005;Cheriton et al, 2007;McManus et al, 2008;Ryan et al, 2008;Cheriton et al, 2009;Ryan et al, 2010). Thin plankton layers have been shown to contain up to 75% of the total biomass in the water column (Holliday et al, 2010;Sullivan et al, 2010b).…”