The influence of variable slope‐water characteristics on dissolved oxygen levels in the northern <scp>C</scp>alifornia <scp>C</scp>urrent <scp>S</scp>ystem

Durski, S. M.; Barth, John A.; McWilliams, James C.; Frenzel, Hartmut; Deutsch, Curtis

doi:10.1002/2017jc013089

Cited by 13 publications

(15 citation statements)

References 33 publications

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“…Distributions of hydrographic variables such as temperature and O 2 over the CCS were reconstructed from Regional Ocean Modeling System (ROMS) simulations that were validated with historical hydrographic observations [ fig. S2 and Supplementary Materials; (15)(16)(17)(18)].…”

Section: Study Approachmentioning

confidence: 99%

“…We used a regional model of the CCS circulation (ROMS) with a Biogeochemical Elemental Cycling model to hindcast physical and biogeochemical variables over the years 1995-2010 (15)(16)(17)(18). The hydrographic variability was extended further back in time by combining high-resolution model fields with long-term, lowerresolution hydrographic observations starting in 1956.…”

Section: Anchovy Observational Datamentioning

confidence: 99%

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Climate-driven aerobic habitat loss in the California Current System

et al. 2020

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Climate warming is expected to intensify hypoxia in the California Current System (CCS), threatening its diverse and productive marine ecosystem. We analyzed past regional variability and future changes in the Metabolic Index (Φ), a species-specific measure of the environment’s capacity to meet temperature-dependent organismal oxygen demand. Across the traits of diverse animals, Φ exhibits strong seasonal to interdecadal variations throughout the CCS, implying that resident species already experience large fluctuations in available aerobic habitat. For a key CCS species, northern anchovy, the long-term biogeographic distribution and decadal fluctuations in abundance are both highly coherent with aerobic habitat volume. Ocean warming and oxygen loss by 2100 are projected to decrease Φ below critical levels in 30 to 50% of anchovies’ present range, including complete loss of aerobic habitat—and thus likely extirpation—from the southern CCS. Aerobic habitat loss will vary widely across the traits of CCS taxa, disrupting ecological interactions throughout the region.

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Section: Study Approachmentioning

confidence: 99%

Section: Anchovy Observational Datamentioning

confidence: 99%

Climate-driven aerobic habitat loss in the California Current System

et al. 2020

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“…The values of Ω A are calculated from model dissolved inorganic carbon (DIC) and total alkalinity (Alk) using carbonate system equilibrium equations (CO 2 SY S) (van Heuven et al, 2011). The variability of O 2 has been analyzed in greater detail using previous simulations of this model with different atmospheric and physical boundary conditions (Durski et al, 2017).…”

Section: Thermoclinementioning

confidence: 99%

Biogeochemical variability in the California Current System

Deutsch

Frenzel

McWilliams

et al. 2020

Preprint

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The biological productivity and diversity of the California Current System (CCS) is at the leading edge of major emerging climate trends, including hypoxia and acidification. We present results from a hindcast simulation (reanalysis) of an eddy-resolving oceanic physicalbiogeochemical model of the CCS, to characterize its mean state and its patterns and drivers of variability in marine biogeochemical and ecosystem processes from 1995-2010. This is a companion paper to a physical analysis in Renault et al. (2019). The model reproduces longterm mean distributions of key ecosystem metrics, including surface nutrients and productivity and subsurface O 2 and carbonate undersaturation. The spatial patterns of Net Primary Productivity (NPP) are broadly consistent with measured and remotely sensed rates, and they reflect a predominant limitation by nitrogen, with seasonal and episodic limitation by F e nearshore in the central CCS, and in the open ocean northern CCS. The vertical distribution of NPP is governed by the trade-off between nutrient and light limitation, a balance that reproduces and explains the observed spatial variations in the depth of the deep Chl maximum. The seasonal to interannual variability of biogeochemical properties and rates is also well captured by model simulations. Because of the prevailing nutrient limitation, fluctuations in the depth of the pycnocline and associated nutricline are the leading single factor explaining interannual variability in the interior biogeochemical state, and the relationships between density and biogeochemical rates and tracers are consistent between model and observations. The magnitude and relationship between density structure and biogeochemical processes is illustrated by the 1997-98 El Niño event, which faithfully reproduces the single largest deviation from the mean state in the simulated period. A slower decadal shoaling of the pycnocline also accounts for the concomitant trends in hypoxic and corrosive conditions on the shelf. The resulting variability is key to understanding the vulnerability of marine species to oceanic change, and to the detection of such changes, soon projected to exceed the range of conditions in the past century.

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“…To better understand the pathways and fluxes of O 2 to the ODZ, we use an eddy-permitting ROMS (Shchepetkin & McWilliams, 2005) with an embedded ecosystem model (Biogeochemical Elemental Cycling, Moore et al, 2004). The model has been extensively validated against numerous observations in the eastern North Pacific (Durski et al, 2017;Renault et al, 2016). The model domain covers the whole Pacific north of~40°S, with a horizontal resolution of 25 km and 32 vertical sigma levels.…”

Section: Ocean Modelmentioning

confidence: 99%

Ventilation Pathways for the North Pacific Oxygen Deficient Zone

Margolskee

Frenzel

Emerson

et al. 2019

Global Biogeochemical Cycles

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Oxygen deficient zones (ODZs) in the tropical ocean exert a profound influence on global biogeochemical cycles, but the factors that regulate their long‐term structure and sensitivity to oceanic change remain poorly understood. We analyzed hydrographic observations and a high‐resolution physical/biogeochemical model to diagnose the primary pathways that ventilate the tropical Pacific ODZs. Historical and recent autonomous observations reveal pronounced and widespread O2 peaks, termed secondary oxygen maxima (SOMs), within the depths of the broader O2 minimum layer, especially at the equatorward edge of both northern and southern ODZs. In the northern ODZ, Lagrangian particle tracking in an eddy‐permitting numerical model simulation attributes these features to intrusions of the Northern Subsurface Countercurrent along the equatorial edge of the ODZ. Zonal subsurface jets also ventilate the poleward edge of the northern ODZ but induce a smaller O2 flux and do not yield detectable SOMs. Along the ODZ's eastern boundary, oxygenation is achieved by the seasonal cycle of upwelling of low‐O2 water onto the continental shelf, followed by downwelling of O2‐replenished near‐surface waters back into the ODZ. Waters entering the northern Pacific ODZ originate from the extratropics in both hemispheres, but two thirds are from the Southern Hemisphere and arrive later and with a wider range of transit times. These results suggest that predicting future changes in the large Pacific ODZs will require a better understanding of the climate sensitivity of the narrow zonal jets and seasonal dynamics of coastal upwelling that supply their O2.

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The influence of variable slope‐water characteristics on dissolved oxygen levels in the northern California Current System

Cited by 13 publications

References 33 publications

Climate-driven aerobic habitat loss in the California Current System

Climate-driven aerobic habitat loss in the California Current System

Biogeochemical variability in the California Current System

Ventilation Pathways for the North Pacific Oxygen Deficient Zone

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