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AGU: Journal of Geophysical Research, Oceans

 

Keywords

  • climate variability
  • pycnocline depth
  • sea surface height

Index Terms

  • Oceanography: Physical: General circulation
  • Oceanography: Physical: Eddies and mesoscale processes
  • Oceanography: Physical: Western boundary currents
  • Oceanography: Physical: Planetary waves
Abstract
Cited By (0)
 

Abstract

Low-frequency variability in the Gulf of Alaska from coarse and eddy-permitting ocean models

Antonietta Capotondi

PSD, ESRL, NOAA, Boulder, Colorado, USA

University of Colorado, Boulder, Colorado, USA

CIRES, Boulder, Colorado, USA

Vincent Combes

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

Michael A. Alexander

PSD, ESRL, NOAA, Boulder, Colorado, USA

Emanuele Di Lorenzo

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

Arthur J. Miller

Scripps Institute of Oceanography, La Jolla, California, USA

An eddy-permitting ocean model of the northeast Pacific is used to examine the ocean adjustment to changing wind forcing in the Gulf of Alaska (GOA) at interannual-to-decadal timescales. It is found that the adjustment of the ocean model in the presence of mesoscale eddies is similar to that obtained with coarse-resolution models. Local Ekman pumping plays a key role in forcing pycnocline depth variability and, to a lesser degree, sea surface height (SSH) variability in the center of the Alaska gyre and in some areas of the eastern and northern GOA. Westward Rossby wave propagation is evident in the SSH field along some latitudes but is less noticeable in the pycnocline depth field. Differences between SSH and pycnocline depth are also found when considering their relationship with the local forcing and leading modes of climate variability in the northeast Pacific. In the central GOA pycnocline depth variations are more clearly related to changes in the local Ekman pumping than SSH. While SSH is marginally correlated with both Pacific Decadal Oscillation (PDO) and North Pacific Gyre Oscillation (NPGO) indices, the pycnocline depth evolution is primarily related to NPGO variability. The intensity of the mesoscale eddy field increases with increasing circulation strength. The eddy field is generally more energetic after the 1976–1977 climate regime shift, when the gyre circulation intensified. In the western basin, where eddies primarily originate from intrinsic instabilities of the flow, variations in eddy kinetic energy are statistically significant correlated with the PDO index, indicating that eddy statistics may be inferred, to some degree, from the characteristics of the large-scale flow.

Received 20 June 2008; accepted 24 October 2008; published 30 January 2009.

Citation: Capotondi, A., V. Combes, M. A. Alexander, E. Di Lorenzo, and A. J. Miller (2009), Low-frequency variability in the Gulf of Alaska from coarse and eddy-permitting ocean models, J. Geophys. Res., 114, C01017, doi:10.1029/2008JC004983.

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