Phenology of coastal upwelling in the California Current

Abstract

[1] Changes in the amplitude and phasing of seasonal events (phenology) can affect the functioning of marine ecosystems. Phenology plays a particularly critical role in eastern boundary ecosystems, which are driven largely by the seasonal cycle of coastal upwelling. Here we develop and describe a set of indicators that quantify the timing, evolution, intensity, and duration of coastal upwelling in the California Current large marine ecosystem (CCLME). There is significant interannual variability in upwelling characteristics during 1967-2007, with extended periods of high (1970s, 1998-2004) and low (1980 -1995) seasonallyintegrated upwelling and a trend towards a later and shorter upwelling season in the northern CCLME. El Niño years were characterized by delayed and weak upwelling in the central CCLME. Understanding the causes and ecosystem consequences of phenological changes in coastal upwelling is critical, as climate models project significant variability in the amplitude and phase of coastal upwelling under varying climate change scenarios.

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

“…This pattern, however, is not static. Over recent decades, the timing of upwelling has trended toward later and shorter upwelling seasons in the northern portion of the California System and longer upwelling seasons in the southern portion (Bograd et al, 2009;García-Reyes and Largier, 2010). In contrast, a modeling study on wind stress curl (Diffenbaugh et al, 2004) found increased (decreased) upwelling in the late season in the northern (southern) California System.…”

“…Moreover, most AOGCMs show poleward expansion of the OHPS in the future (Diffenbaugh, 2005;Lu et al, 2007;Garreaud and Falvey, 2009;Echevin et al, 2012;Belmadani et al, 2014) caused by poleward expansion of the Hadley Cells in both hemispheres (Lu et al, 2007;Seager et al, 2010), and intensification of the OHPS in the northern hemisphere (Li et al, 2012). While one study using reanalysis data shows no evidence of trends in the position of mid-latitude atmospheric pressure centers over the past decades (Stocker et al, 2013), the prominent natural variability in the position of these systems over decadal time scales might mask potential trends (Bograd et al, 2009;Gutiérrez et al, 2011;Santos et al, 2012;Stocker et al, 2013). Understanding and predicting the intensity and position of OHPS is of great importance to the ecology of EBUS (Schroeder et al, 2013(Schroeder et al, , 2014, making this area ripe for future analyses.…”

Δ14C and Δ13C of Seawater DIC as Tracers of Coastal Upwelling: A 5-Year Time Series from Southern California

“…This strong, seasonal upwelling is characteristic of the entire western coastline of North America and affects primary productivity by supplying cold, nutrient-rich water to the ocean surface close to the coastline. The timing and intensity of seasonal upwelling varies on decadal (Chhak and Di Lorenzo 2007) and shorter timescales (Legaard and Thomas 2007), and substantial changes (such as timing, intensity, or duration of upwelling) can interfere with the entire marine ecosystem in this region (Brodeur et al 2006;Bograd et al 2009). Recently, strong El Niño events have led to significantly decreased upwelling, decreased wind-driven mixing, and a weakening of the California Current (Lynn et al 1995;Bograd and Lynn 2001), in conjunction with increased rainfall in California and significant negative impacts on marine ecosystems (Chavez et al 2002).…”

Environmental conditions impacting juvenile Chinook salmon growth off central California: An ecosystem model analysis

“…In fact, the model results suggest that, based on alongshore wind properties directly offshore of the GOF, none of the standard metrics based on cumulative upwelling [Bograd et al, 2009] provides a useful proxy for distinguishing between favorable and unfavorable growth conditions.…”

“…Alongshore wind is a proxy for total upwelling intensity similar to that defined by Bograd et al [2009] and based on the Bakun upwelling index. Based on the model simulations, neither the date of the spring transition, length of the upwelling season, nor total cumulative upwelling emerged as reliable proxies for environmental conditions favoring juvenile salmon growth (Table 1).…”