Spatially resolved upwelling in the California Current System and its connections to climate variability

Abstract

A historical analysis of California Current System (CCS) circulation, performed using the Regional Ocean Modeling System with four‐dimensional variational data assimilation, was used to study upwelling variability during the 1988–2010 period. We examined upwelling directly from the vertical velocity field, which elucidates important temporal and spatial variability not captured by traditional coastal upwelling indices. Through much of the CCS, upwelling within 50 km of the coast has increased, as reported elsewhere. However, from 50 to 200 km offshore, upwelling trends are negative and interannual variability is 180° out of phase with the nearshore signal. This cross‐shore pattern shows up as the primary mode of variability in central and northern CCS vertical velocity anomalies, accounting for ∼40% of the total variance. Corresponding time series of the dominant modes in the central and northern CCS are strongly correlated with large‐scale climate indices, suggesting that climate fluctuations may alternately favor different biological communities.

Under Pressure: Climate Change, Upwelling, and Eastern Boundary Upwelling Ecosystems

“…Those containing seemingly contradictory results (Demarcq, 2009;Dewitte et al, 2012) add uncertainty, but do not refute the findings of the metaanalysis, as they focus on local regions, use short time series and do not add uncertainty. Despite the fact that the meta-analysis by Sydeman et al generally supports Bakun's proposition, we still cannot attribute coastal wind intensification in EBUS to global warming because we cannot discount the role of multi-decadal climate variability in the observed trends (Chhak and Di Lorenzo, 2007;Narayan et al, 2010;Pérez et al, 2010;Macias et al, 2012;Santos et al, 2012;Cropper et al, 2014;Jacox et al, 2014), nor is it a test of the Bakun hypothesis mechanism.…”

“…Importantly, there is stronger agreement that significant trends of upwelling intensification are evident at higher latitude for all EBUS. Among studies excluded from the meta-analysis, either because they did not meet the strict selection criteria or because they were published after the analysis was completed, most (Di Lorenzo et al, 2005;Alves and Miranda, 2013;Barton et al, 2013;Bylhouwer et al, 2013;Stocker et al, 2013;Cropper et al, 2014;deCastro et al, 2014;Jacox et al, 2014;Sydeman et al, 2014b;Varela et al, 2015) show results consistent with the findings of Sydeman et al (2014a). Those containing seemingly contradictory results (Demarcq, 2009;Dewitte et al, 2012) add uncertainty, but do not refute the findings of the metaanalysis, as they focus on local regions, use short time series and do not add uncertainty.…”

On the skill of seasonal sea surface temperature forecasts in the California Current System and its connection to ENSO variability

“…(1) a horizontal grid resolution of order 1° in the ocean is too coarse to resolve the cross-shore scales of coastal upwelling (Jacox et al 2014) and the temperature variability that comes with it (Fig. 1).…”

“…These dynamics are sensitive to temporal variability on scales from daily weather to multi-decadal and secular change (Checkley and Barth 2009). In particular, leading modes of basin-scale climate variability including the El Niño-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and the North Pacific Gyre Oscillation (NPGO) exert strong control over CCS upwelling (Di Lorenzo et al 2008;Jacox et al 2014Jacox et al , 2015b, generating pronounced interannual variability in the nearshore environment ( Fig. 1) and its biological communities.…”

Response of O<sub>2</sub> and pH to ENSO in the California Current System in a high-resolution global climate model

“…A handful of observational studies have investigated the impact of the 1982/1983 El Niño on the physical regime of the CalCS (e.g., Simpson, 1983;Huyer and Smith, 1985) and the effect of the 2002/2003 El Niño on the physics and biology (e.g., Murphree et al, 2003;Schwing et al, 2002a). Several regional modeling studies have shown the connection between ENSO and the vertical transport, water column density, origins, and properties of upwelled water (Jacox et al, 2014(Jacox et al, , 2015b, and demonstrated the relative importance of remote versus local forcing on both the physics and the biogeochemistry of the CalCS (Frischknecht et al, 2015;Jacox et al, 2015a;Frischknecht et al, 2017). During the 2010/2011 La Niña, Nam et al (2011) observed decreases in O 2 and pH in the upwelling region along the coast that were 2-3 times larger than expected solely due to the cross-shore shoaling of the isopycnal surfaces.…”