Oxygen in the Southern California Bight: Multidecadal trends and implications for demersal fisheries

McClatchie, Sam; Goericke, Ralf; Cosgrove, Ronán; Auad, Guillermo; Vetter, Russell D.

doi:10.1029/2010gl044497

Cited by 122 publications

(113 citation statements)

References 15 publications

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“…For example, a time series of upwelling favorable winds and sea surface T suggests that a strengthening of large-scale pressure gradient fields led to increased and protracted upwelling in parts of the central CCS (García-Reyes and Largier, 2010), which in turn would lead to lower surface pH and arag , further exacerbating the effects of increasing pCO 2 on the CCS. In addition to increased aragonite undersaturation, shoaling of low oxygen waters further minimizes habitats of sensitive organisms (Bograd et al, 2008;McClatchie et al, 2010). Oxygen declines in the CCS result from decreasing concentrations of oxygen in the Equatorial and Eastern Pacific (Stramma et al, 2008(Stramma et al, , 2010Bograd et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

Spatiotemporal variability and long-term trends of ocean acidification in the California Current System

et al. 2013

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Abstract. Due to seasonal upwelling, the upper ocean waters of the California Current System (CCS) have a naturally low pH and aragonite saturation state ( arag ), making this region particularly prone to the effects of ocean acidification. Here, we use the Regional Oceanic Modeling System (ROMS) to conduct preindustrial and transient simulations of ocean biogeochemistry in the CCS. The transient simulations were forced with increasing atmospheric pCO 2 and increasing oceanic dissolved inorganic carbon concentrations at the lateral boundaries, as projected by the NCAR CSM 1.4 model for the IPCC SRES A2 scenario. Our results show a large seasonal variability in pH (range of ∼ 0.14) and arag (∼ 0.2) for the nearshore areas (50 km from shore). This variability is created by the interplay of physical and biogeochemical processes. Despite this large variability, we find that present-day pH and arag have already moved outside of their simulated preindustrial variability envelopes (defined by ±1 temporal standard deviation) due to the rapidly increasing concentrations of atmospheric CO 2 . The nearshore surface pH of the northern and central CCS are simulated to move outside of their present-day variability envelopes by the mid-2040s and late 2030s, respectively. This transition may occur even earlier for nearshore surface arag , which is projected to depart from its present-day variability envelope by the early-to mid-2030s. The aragonite saturation horizon of the central CCS is projected to shoal into the upper 75 m within the next 25 yr, causing near-permanent undersaturation in subsurface waters. Due to the model's overestimation of arag , this transition may occur even earlier than simulated by the model. Overall, our study shows that the CCS joins the Arctic and Southern oceans as one of only a few known ocean regions presently approaching the dual threshold of widespread and near-permanent undersaturation with respect to aragonite and a departure from its variability envelope. In these regions, organisms may be forced to rapidly adjust to conditions that are both inherently chemically challenging and also substantially different from past conditions.

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Section: Discussionmentioning

confidence: 99%

Spatiotemporal variability and long-term trends of ocean acidification in the California Current System

et al. 2013

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“…Here, decreased pH of shelf waters has been associated with strong upwelling at interannual scales (Feely et al, 2008), though longer-term data are generally not available. Over longer periods, decadal-scale changes in ventilation and source-water properties have likely resulted in decreased oxygen concentrations and shoaling of the oxygen minimum layer in the California (Bograd et al, 2008;McClatchie et al, 2010) and Benguela Systems (Monteiro et al, 2008;Salvanes et al, 2015). Such changes, however, have also been associated with known modes of decadal variability in oceanatmosphere processes (Deutsch et al, 2005;Chhak and Di Lorenzo, 2007).…”

Section: Upwelling Stratification and Biogeochemistrymentioning

confidence: 99%

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

et al. 2015

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The IPCC AR5 provided an overview of the likely effects of climate change on Eastern Boundary Upwelling Systems (EBUS), stimulating increased interest in research examining the issue. We use these recent studies to develop a new synthesis describing climate change impacts on EBUS. We find that model and observational data suggest coastal upwelling-favorable winds in poleward portions of EBUS have intensified and will continue to do so in the future. Although evidence is weak in data that are presently available, future projections show that this pattern might be driven by changes in the positioning of the oceanic high-pressure systems rather than by deepening of the continental low-pressure systems, as previously proposed. There is low confidence regarding the future effects of climate change on coastal temperatures and biogeochemistry due to uncertainty in the countervailing responses to increasing upwelling and coastal warming, the latter of which could increase thermal stratification and render upwelling less effective in lifting nutrient-rich deep waters into the photic zone. Although predictions of ecosystem responses are uncertain, EBUS experience considerable natural variability and may be inherently resilient. However, multi-trophic level, end-to-end (i.e., "winds to whales") studies are needed to resolve the resilience of EBUS to climate change, especially their response to long-term trends or extremes that exceed pre-industrial ranges.

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“…The 26.44 isopycnal was chosen from the average density (26.44 6 0.12) of the salinity-based upwelling depths. The 150 m depth stratum was chosen to coincide with historic estimates of the deepest depth for upwelled water (Huyer 1983) and to maintain consistency with similar studies conducted in other regions of the California Current (McClatchie et al 2010).…”

Section: Methodsmentioning

confidence: 99%

Seasonal and interannual variation in the extent of hypoxia in the northern California Current from 1998–2012

Peterson

Morgan

Peterson

et al. 2013

Limnology & Oceanography

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This study addresses the occurrence, severity, and extent of hypoxia over the continental shelf of the northern California Current (40-48.5uN latitude) from 1998 to 2012. Clear seasonal trends exist in the timing and duration of hypoxia. The highest bottom-water dissolved oxygen concentrations occurred from November to March, and levels below the 1.4 mL L 21 hypoxia threshold were detected during the upwelling season (May through October). Regions of hypoxia tended to occur north of 42uN latitude and were most severe over the widest areas of the continental shelf. Hypoxic waters covered up to 62% (15,600 km 2 ) of the continental shelf during some years

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Oxygen in the Southern California Bight: Multidecadal trends and implications for demersal fisheries

Cited by 122 publications

References 15 publications

Spatiotemporal variability and long-term trends of ocean acidification in the California Current System

Spatiotemporal variability and long-term trends of ocean acidification in the California Current System

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

Seasonal and interannual variation in the extent of hypoxia in the northern California Current from 1998–2012

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