Open AccessCoupled Ocean–Atmosphere Response to Idealized Freshwater Forcing over the Western Tropical Pacific
Author(s) -
Lixin Wu,
Yan Sun,
Jiaxu Zhang,
Liping Zhang,
Shoshiro Minobe
Publication year - 2010
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 - 10.1175/2009jcli3009.1
Subject(s) - climatology , teleconnection , extratropical cyclone , forcing (mathematics) , pacific decadal oscillation , advection , atmosphere (unit) , environmental science , sea surface temperature , tropics , geology , walker circulation , ocean current , tropical eastern pacific , thermohaline circulation , oceanography , pacific ocean , el niño southern oscillation , geography , meteorology , physics , fishery , biology , thermodynamics
The coupled ocean–atmosphere responses to idealized freshwater forcing in the western tropical Pacific are studied using a fully coupled climate model. The model explicitly demonstrates that freshwater forcing in the western tropical Pacific can lead to a basinwide response with the pattern resembling the Pacific decadal oscillation. In the tropics, a negative (positive) freshwater forcing over the western tropical Pacific decreases (increases) sea surface height locally, and sets up a positive (negative) zonal pressure gradient anomaly, which accelerates (decelerates) the meridional overturning circulation and equatorial surface westward flow. This leads to an intensification (reduction) of meridional heat divergence and vertical cold advection, and thus a development of La Niña (El Niño)–like responses in the tropics. The tropical responses are further substantiated by the positive Bjerknes feedback, and subsequently force significant changes in the extratropical North Pacific through atmospheric teleconnection. The local freshwater response also reinforces the imposed forcing, forming a positive feedback loop. Applications to Pacific climate changes are discussed.