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AGU: Geophysical Research Letters

 

Index Terms

  • Oceanography: General: Descriptive and regional oceanography
  • Oceanography: General: Climate and interannual variability
  • Oceanography: General: Diurnal, seasonal, and annual cycles
  • Oceanography: Physical: Fronts and jets
  • Oceanography: Biological and Chemical: General or miscellaneous

Abstract

On the seasonal and interannual migrations of the transition zone chlorophyll front

Steven J. Bograd

Pacific Fisheries Environmental Laboratory, NOAA National Marine Fisheries Service, Pacific Grove, California, USA

David G. Foley

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

Franklin B. Schwing

Pacific Fisheries Environmental Laboratory, NOAA National Marine Fisheries Service, Pacific Grove, California, USA

Cara Wilson

Pacific Fisheries Environmental Laboratory, NOAA National Marine Fisheries Service, Pacific Grove, California, USA

R. Michael Laurs

Pacific Fisheries Environmental Laboratory, NOAA National Marine Fisheries Service, Pacific Grove, California, USA

Jeffrey J. Polovina

Pacific Islands Fisheries Science Center, NOAA National Marine Fisheries Service, Honolulu, Hawaii, USA

Evan A. Howell

Pacific Islands Fisheries Science Center, NOAA National Marine Fisheries Service, Honolulu, Hawaii, USA

Russell E. Brainard

Pacific Islands Fisheries Science Center, NOAA National Marine Fisheries Service, Honolulu, Hawaii, USA

High-resolution satellite measurements of ocean color and surface winds, along with historical in situ data, are used to explore interannual variability in the annual migration of the transition zone chlorophyll front (TZCF) in the central North Pacific Ocean. Significant variations in frontal position and annual range were observed, including a significant southerly displacement during El Niño events. This displacement, apparently forced by enhanced surface convergence and vertical mixing in the transition zone, creates vast regions of anomalously high wintertime surface chlorophyll in the North Pacific Subtropical Gyre. A remarkably close correspondence between the positions of the TZCF and the 18°C surface isotherm over a portion of the central North Pacific allows historical temperature data to be used as a proxy for TZCF position. This surface temperature proxy has revealed decadal-scale variability in frontal position, with greater (lesser) annual range and southerly extent following the large-scale 1976–77 (1998–99) climate shifts. Interannual variations in TZCF position could have important implications for the distribution and survival of a number of apex predators that utilize the TZCF as a migratory and foraging habitat.

Received 31 May 2004; accepted 9 August 2004; published 2 September 2004.

Citation: Bograd, S. J., D. G. Foley, F. B. Schwing, C. Wilson, R. M. Laurs, J. J. Polovina, E. A. Howell, and R. E. Brainard (2004), On the seasonal and interannual migrations of the transition zone chlorophyll front, Geophys. Res. Lett., 31, L17204, doi:10.1029/2004GL020637.

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