Open AccessKuroshio Extension Bimodality and the North Pacific Oscillation: A Case of Intrinsic Variability Paced by External Forcing
Author(s) -
Stefano Pierini
Publication year - 2014
Publication title -
journal of climate
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.315
H-Index - 287
eISSN - 1520-0442
pISSN - 0894-8755
DOI - 10.1175/jcli-d-13-00306.1
Subject(s) - forcing (mathematics) , climatology , rossby wave , bimodality , geology , amplitude , teleconnection , oscillation (cell signaling) , ocean general circulation model , physics , general circulation model , el niño southern oscillation , oceanography , climate change , quantum mechanics , galaxy , biology , genetics
A previous North Pacific Ocean circulation model forced by climatological winds is extended here to include\uda time-dependent North Pacific Oscillation (NPO) forcing. The Kuroshio Extension (KE) decadal\udbimodal cycle (which is a self-sustained intrinsic relaxation oscillation in the climatologically forced case) is\udnow excited by the NPO forcing. Both the timing of the cycles and the Rossby wave teleconnection mechanism\udthat is found to govern the synchronization from 1993 to 2012 are in good agreement with altimeter\udobservations. Sensitivity numerical experiments are carried out by varying the zonal location and amplitude\udof the NPO forcing, and the lateral eddy viscosity. The emergence of the KE bimodality with a correct timing\udis found to be extremely sensitive to changes in the dissipative parameterization; the implications of such\udsensitivity for deficiencies found in more realistic North Pacific Ocean general circulation models are discussed.\udThe dynamical mechanism that emerges from this study is explained as a case of intrinsic variability in\udan excitable dynamical system triggered, and therefore paced, by an external forcing