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AGU: Geophysical Research Letters

 

Keywords

  • California Current System
  • CalCOFI
  • dissolved oxygen
  • oxygen minimum layer
  • hypoxia

Index Terms

  • Oceanography: Biological and Chemical: Hypoxic environments
  • Oceanography: Physical: Eastern boundary currents
  • Oceanography: General: Coastal processes
  • Oceanography: General: Physical and biogeochemical interactions
  • Oceanography: General: Climate and interannual variability

Abstract

Oxygen declines and the shoaling of the hypoxic boundary in the California Current

Steven J. Bograd

Environmental Research Division, Southwest Fisheries Science Center, NOAA, Pacific Grove, California, USA

Carmen G. Castro

Instituto de Investigaciones Marinas, Consejo Superior de Investigaciones Científicas, Vigo, Spain

Emanuele Di Lorenzo

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA

Daniel M. Palacios

Environmental Research Division, Southwest Fisheries Science Center, NOAA, Pacific Grove, California, USA

Joint Institute for Marine and Atmospheric Research, University of Hawaii at Manoa, Honolulu, Hawaii, USA

Helen Bailey

Environmental Research Division, Southwest Fisheries Science Center, NOAA, Pacific Grove, California, USA

William Gilly

Hopkins Marine Station, Stanford University, Pacific Grove, California, USA

Francisco P. Chavez

Monterey Bay Aquarium Research Institute, Moss Landing, California, USA

We use hydrographic data from the California Cooperative Oceanic Fisheries Investigations program to explore the spatial and temporal variability of dissolved oxygen (DO) in the southern California Current System (CCS) over the period 1984–2006. Large declines in DO (up to 2.1 μmol/kg/y) have been observed throughout the domain, with the largest relative DO declines occurring below the thermocline (mean decrease of 21% at 300 m). Linear trends were significant (p < 0.05) at the majority of stations down to 500 m. The hypoxic boundary (∼60 μmol/kg) has shoaled by up to 90 m within portions of the southern CCS. The observed trends are consistent with advection of low-DO waters into the region, as well as decreased vertical oxygen transport following near-surface warming and increased stratification. Expansion of the oxygen minimum layer could lead to cascading effects on benthic and pelagic ecosystems, including habitat compression and community reorganization.

Received 31 March 2008; accepted 30 April 2008; published 28 June 2008.

Citation: Bograd, S. J., C. G. Castro, E. Di Lorenzo, D. M. Palacios, H. Bailey, W. Gilly, and F. P. Chavez (2008), Oxygen declines and the shoaling of the hypoxic boundary in the California Current, Geophys. Res. Lett., 35, L12607, doi:10.1029/2008GL034185.

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