Journal of Oceanography

, Volume 68, Issue 1, pp 127–137

Response of the North Pacific subtropical countercurrent and its variability to global warming

  • Lixiao Xu
  • Shang-Ping Xie
  • Qinyu Liu
  • Fumiaki Kobashi
Special Section: Original Article New developments in mode-water research: Dynamic and climatic effects

Abstract

Response of the North Pacific subtropical countercurrent (STCC) and its variability to global warming is examined in a state-of-the-art coupled model that is forced by increasing greenhouse gas concentrations. Compared with the present climate, the upper ocean is more stratified, and the mixed layer depth (MLD) shoals in warmer climate. The maximum change of winter MLD appears in the Kuroshio–Oyashio extension (KOE) region, where the mean MLD is the deepest in the North Pacific. This weakens the MLD front and reduces lateral induction. As a result of the reduced subduction rate and a decrease in sea surface density in KOE, mode waters form on lighter isopycnals with reduced thickness. Advected southward, the weakened mode waters decelerate the STCC. On decadal timescales, the dominant mode of sea surface height in the central subtropical gyre represents STCC variability. This STCC mode decays as CO2 concentrations double in the twenty-first century, owing both to weakened mode waters in the mean state and to reduced variability in mode waters. The reduced mode-water variability can be traced upstream to reduced variations in winter MLD front and subduction in the KOE region where mode water forms.

Keywords

North Pacific subtropical countercurrent Global warming Decadal variability Mode waters Subduction rate Mixed layer depth 

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Copyright information

© The Oceanographic Society of Japan and Springer 2011

Authors and Affiliations

  • Lixiao Xu
    • 1
  • Shang-Ping Xie
    • 1
    • 2
  • Qinyu Liu
    • 1
  • Fumiaki Kobashi
    • 3
    • 4
  1. 1.Physical Oceanography Laboratory, and Ocean–Atmosphere Interaction and Climate LaboratoryQingdaoChina
  2. 2.Department of Meteorology, International Pacific Research CenterUniversity of Hawaii at ManoaHonoluluHawaii
  3. 3.Faculty of Marine TechnologyTokyo University of Marine Science and TechnologyTokyoJapan
  4. 4.Research Institute for Global ChangeJapan Agency for Marine-Earth Science and TechnologyYokosukaJapan

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