Pacific subtropical‐tropical thermocline water exchange in the National Centers for Environmental Prediction ocean model

Huang, Boyin; Liu, Zhengyu

doi:10.1029/1999jc900024

Cited by 52 publications

(52 citation statements)

References 29 publications

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“…The two selected domains ( Fig. 2) are in the regions of subduction windows (Liu et al 1994;Gu and Philander 1997;Huang and Liu 1999). In selecting the size of the forcing domains, the relative coarse horizontal resolution of the coupled model was also taken into consideration.…”

Section: Model and Experimental Setupmentioning

confidence: 99%

Subtropical Forcing of Tropical Pacific Climate and Decadal ENSO Modulation

et al. 2008

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The relative impact of the subtropical North and South Pacific Oceans on the tropical Pacific climate mean state and variability is estimated using an ocean-atmosphere-sea ice coupled general circulation model. Tailored experiments are performed in which the model is forced by idealized sea surface temperature anomalies (SSTAs) in the subtropics of both hemispheres. The main results of this study suggest that subtropical South Pacific climate variations play a dominant role in tropical Pacific decadal variability and in the decadal modulation of El Niño-Southern Oscillation (ENSO).In response to a 2°C warming in the subtropical South Pacific, the equatorial Pacific SST increases by about 0.6°C, approximately 65% larger than the change in the North Pacific experiment. The subtropics affect equatorial SST mainly through atmosphere-mixed layer interactions in the South Pacific experiments; the response is mostly accomplished within a decade. The "oceanic tunnel" dominates in the North Pacific experiments; the response takes at least 100 yr to be accomplished. Similar sensitivity experiments conducted with the stand-alone atmosphere model showed that both air-sea interactions and ocean dynamics are crucial in shaping the tropical climate response.The statistics of ENSO exhibit significant changes in amplitude and frequency in response to a warming/ cooling of the subtropical South Pacific: a 2°C warming (cooling) of subtropical South Pacific SST reduces (increases) the interannual standard deviation by about 30% (20%) and shortens (lengthens) the ENSO period. The simulated changes in the equatorial zonal SST gradient are the main contributor to the modulation of ENSO variability. The simulated intensification (weakening) of the annual cycle in response to an enhanced warming (cooling) in subtropical South Pacific partly explains the shifts in frequency, but may also lead to a weaker (stronger) ENSO. The subtropical North Pacific thermal forcing did not change the statistical properties of ENSO as strongly.

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Section: Model and Experimental Setupmentioning

confidence: 99%

Subtropical Forcing of Tropical Pacific Climate and Decadal ENSO Modulation

et al. 2008

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“…Johnson and McPhaden (1999) used historical CTD data to analyze IPs. Results from data-assimilated OGCM were discussed by Huang and Liu (1999). These studies reveal important dynamical aspects of these pathways, but many questions remain unanswered.…”

Section: Introductionmentioning

confidence: 99%

“…Despite different times used in the calculations, these results are consistent. The NCEP data used by Huang and Liu (1999) From Fig. 5 we can also see that windIPTs in both hemispheres increase equatorward.…”

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confidence: 99%

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Decadal Variability of Pycnocline Flows from the Subtropical to the Equatorial Pacific*

Wang

Huang

2005

Journal of Physical Oceanography

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A method based on isopycnal trajectory analysis is proposed to quantify the pathways from the subtropics to the Tropics. For a continuous stratified ocean a virtual streamfunction is defined, which can be used to characterize these pathways. This method is applied to the climatological dataset produced from a dataassimilated model. Analysis indicates that in each layer contours of the virtual streamfunction are a good approximation for streamlines, even if there is a cross-isopycnal mass flux. The zonal-integrated meridional transport per unit layer thickness through each pathway varies in proportion to 1/sin, where is latitude. The vertical-integrated total transport through pathways behaves similarly. Transport through pathways has a prominent decadal variability. Results suggest that in decadal time scales the interior pathway transport (IPT) anomaly may be mainly caused by the wind stress anomaly at low latitude. The western boundary pathway transport (WBPT) anomaly often has a sign opposite to the IPT anomaly, reflecting compensation between the IPT and the WBPT. However, more often than not the wind stress anomaly within tropical latitudes can also be used to explain the WBPT anomaly.

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“…This can be understood as ventilation of the warmer SST signal from extratropical Southern Pacific in austral winter at perihelion (when 30 precession index reaches a minimum) (Liu et al, 2014). The less important role of mean stratification in Ekman pumping feedback may therefore be caused by the acceleration technique: in real time, it takes decades for the subtropical Pacific Ocean to affect the equatorial temperature through the subduction process (Huang and Liu, 1999); in the accelerated time, Clim. Past Discuss., doi :10.5194/cp-2016-128, 2017 Manuscript under review for journal Clim.…”

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confidence: 99%

Evolution and forcing mechanisms of ENSO over the last 300,000 years in CCSM3

Liu

Chen

et al. 2017

Preprint

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Abstract. The responses of El Niño-Southern Oscillation (ENSO) and the equatorial Pacific annual cycle to external forcing changes are studied in three 3,000-year-long NCAR-CCSM3 model simulations. The simulations represent the period from 300 thousand years before present (ka BP) to present day. The first idealized simulation is forced only with accelerated 10 orbital variations, and the rest are conducted more realistically by further adding on the time-varying boundary conditions of greenhouse gases (GHGs) and continental ice sheets.It is found that orbital forcing dominates slow ENSO evolution, while the effects of GHGs and ice-sheet forcing tend to compensate each other. On the orbital time scales, ENSO variability and annual cycle amplitude change in-phase and both 15 have pronounced precessional cycles (~21,000 years) modulated by variations of eccentricity. Orbital forced ENSO intensity is dominated linearly by the change of the coupled ocean-atmosphere instability, notably the Ekman upwelling feedback and the thermocline feedback; and is also possibly affected during ENSO intrinsic developing season by the remote (or extratropical) influences of the short-scale stochastic weather noises. The acceleration technique is found to dampen the precessional signal in ENSO intensity. 20In glacial-interglacial cycles, additionally, the weakening/strengthening of ENSO owning to a more concentrated/depleted GHGs level leaves little net signal as compensated by the effect coherent change of decaying/expanding ice sheets. They influence the ENSO variability through changes in annual cycle amplitude via a common nonlinear frequency entrainment mechanism while the GHGs effect might has an additional linear part. 25Clim. Past Discuss.,

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Pacific subtropical‐tropical thermocline water exchange in the National Centers for Environmental Prediction ocean model

Cited by 52 publications

References 29 publications

Subtropical Forcing of Tropical Pacific Climate and Decadal ENSO Modulation

Subtropical Forcing of Tropical Pacific Climate and Decadal ENSO Modulation

Decadal Variability of Pycnocline Flows from the Subtropical to the Equatorial Pacific*

Evolution and forcing mechanisms of ENSO over the last 300,000 years in CCSM3

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