Special Section: Original Article New developments in mode-water research: Dynamic and climatic effects

Journal of Oceanography

, Volume 68, Issue 1, pp 93-111

First online:

Interannual variations of the Hawaiian Lee Countercurrent induced by potential vorticity variability in the subsurface

  • Hideharu SasakiAffiliated withEarth Simulator Center, JAMSTEC Email author 
  • , Shang-Ping XieAffiliated withInternational Pacific Research Center and Department of Meteorology, University of Hawaii at Manoa
  • , Bunmei TaguchiAffiliated withEarth Simulator Center, JAMSTEC
  • , Masami NonakaAffiliated withResearch Institute for Global Change, JAMSTEC
  • , Shigeki HosodaAffiliated withResearch Institute for Global Change, JAMSTEC
  • , Yukio MasumotoAffiliated withResearch Institute for Global Change, JAMSTEC

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Interannual variations of the Hawaiian Lee Countercurrent (HLCC) in the 2000s were investigated using satellite and Argo profiling float observations. The satellite-observed sea surface height shows that the geostrophic eastward current was anomalously strong to the west away from Hawaii in 2003 and 2005. However, the trade winds and the orographic wind curl dipole in the lee of Hawaii that drives the climatological mean HLCC were not particularly strong in these years, suggesting that the accelerations of the HLCC were not caused by the wind stress curl forcing around Hawaii and subsequent Rossby wave propagation. Using Argo observations, we found negative potential vorticity (PV) anomalies in the subsurface north of the HLCC in these 2 years. The pycnocline is lifted northward as low PV waters of different densities stack up in the vertical, and the HLCC is then accelerated via the thermal wind. The intensification and/or southward intrusion of the eastern subtropical mode water and subtropical mode water seem to have induced negative PV anomalies in 2003 and 2005, respectively. Using high-resolution ocean simulations, we confirmed the migrations of PV anomalies and their contributions to the HLCC accelerations. Although the HLCC is located away from the cores of major mode waters, our results suggest that interannual variations of the HLCC are affected by those of mode waters.


Hawaiian Lee Countercurrent Low potential vorticity water Interannual variations High-resolution ocean simulation