Impact of freshening over the Southern Ocean on <scp>ENSO</scp>

Ma, Hao; Wu, Lixin; Li, Zhengquan

doi:10.1002/asl2.410

Cited by 8 publications

(9 citation statements)

References 30 publications

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“…These studies have demonstrated that FWF and its related salinity fields first affect the oceanic density gradients and stratification, and then have the ability to maintain the mean climate and its variability (e.g., Maes, 2000;Lagerloef, 2002;Curry et al, 2003;Boyer et al, 2005;Levitus et al, 2005;Ballabrera-Poy et al, 2007;Cravatte et al, 2009;Collins et al, 2010). For instance, sensitivity analyses following an introduction of FWF perturbation have revealed obvious effects on SSTs (Levitus, 1989;Delcroix and Hénin, 1991;Manabe and Stouffer, 1995;Béthoux et al, 1998;Maes, 1998;Wong et al, 1999Wong et al, , 2001Dickson et al, 2002;Jacobs et al, 2002;Fedorov et al, 2004;Ma et al, 2013). In considering the coupling between the ocean and atmosphere, some additional processes start to act because the FWF forcing-induced changes in SSTs can produce additional feedback to the atmosphere.…”

Section: Introductionmentioning

confidence: 97%

Quantitative analysis of the feedback induced by the freshwater flux in the tropical Pacific using CMIP5

2015

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Freshwater flux (FWF) directly affects sea surface salinity (SSS) and hence modulates sea surface temperature (SST) in the tropical Pacific. This paper quantifies a positive correlation between FWF and SST using observations and simulations of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) to analyze the interannual variability in the tropical Pacific. Comparisons among the displacements of FWF, SSS and SST interannual variabilities illustrate that a large FWF variability is located in the west-central equatorial Pacific, covarying with a large SSS variability, whereas a large SST variability is located in the eastern equatorial Pacific. Most CMIP5 models can reproduce the fact that FWF leads to positive feedback to SST through an SSS anomaly as observed. However, the difference in each model's performance results from different simulation capabilities of the CMIP5 models in the magnitudes and positions of the interannual variabilities, including the mixed layer depth and the buoyancy flux in the equatorial Pacific. SSS anomalies simulated from the CMIP5 multi-model are sensitive to FWF interannual anomalies, which can lead to differences in feedback to interannual SST variabilities. The relationships among the FWF, SSS and SST interannual variabilities can be derived using linear quantitative measures from observations and the CMIP5 multi-model simulations. A 1 mm d −1 FWF anomaly corresponds to an SSS anomaly of nearly 0.12 psu in the western tropical Pacific and a 0.11 • C SST anomaly in the eastern tropical Pacific.

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Section: Introductionmentioning

confidence: 97%

Quantitative analysis of the feedback induced by the freshwater flux in the tropical Pacific using CMIP5

2015

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“…Today, it is poised at shallow depths. As a consequence, small changes in its depth through east-west tilting regulated by short-term climate phenomena such as the El Niño-Southern Oscillation can affect surface-water properties and ocean-atmosphere exchange processes (Fedorov et al, 2004;Ma et al, 2013). In general, proxy records and modeling results consistently document a long-term shoaling of the thermocline in the EEP and other (sub-)tropical upwelling regions throughout the Plio-Pleistocene (Wara et al, 2005;Fedorov et al, 2006;Steph et al, 2006aSteph et al, , 2010Dekens et al, 2007;Ford et al, 2012).…”

Section: Introductionmentioning

confidence: 86%

Thermocline state change in the eastern equatorial Pacific during the late Pliocene/early Pleistocene intensification of Northern Hemisphere glaciation

et al. 2018

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Abstract. The late Pliocene/early Pleistocene intensification of Northern Hemisphere glaciation (iNHG) ∼ 2.5 million years ago (marine isotope stages, MIS, 100-96) stands out as an important tipping point in Earth's climate history, which strongly influenced oceanographic and climatic patterns including trade wind and upwelling strength in the eastern equatorial Pacific (EEP). The thermocline depth in the EEP, in turn, plays a pivotal role in the Earth's climate system: small changes in its depth associated with short-term climate phenomena such as the El Niño-Southern Oscillation can affect surface-water properties and the ocean-atmosphere exchange. However, thermocline dynamics in the EEP during the iNHG still remain unclear. While numerous studies have suggested a link between a thermocline shoaling in the EEP and Northern Hemisphere ice growth, other studies have indicated a stable thermocline depth during the iNHG; consequently, a causal relationship between thermocline dynamics and ice-sheet growth has been excluded. In light of these contradictory views, we have generated geochemical (planktic foraminiferal δ 18 O, δ 13 C and Mg / Ca), sedimentological (sand accumulation rates) and faunal (abundance data of thermocline-dwelling foraminifera) records for Ocean Drilling Program Site 849 located in the central region of the EEP. Our records span the interval from ∼ 2.75 to 2.4 Ma (MIS G7-95), which is critical for understanding thermocline dynamics during the final phase of the iNHG. Our new records document a thermocline shoaling from ∼ 2.64 to 2.55 Ma (MIS G2-101) and a relatively shallow thermocline from ∼ 2.55 Ma onwards . This indicates a state change in thermocline depth at Site 849 shortly before the final phase of the iNHG. Ultimately, our data support the hypothesis that (sub-)tropical thermocline shoaling may have contributed to the development of large Northern Hemisphere ice sheets.

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“…Here we extend on previous work (e.g., Ma et al, 2013) by employing a state-of-the-science coupled climate model at relatively high spatial resolution and test a range of meltwater fluxes that are realistic in light of estimated past and future changes in the AIS. We focus specifically on the simulated changes at low latitudes resulting from the meltwater-induced changes in SH high-latitude surface conditions and the relationship between the magnitude of the meltwater-induced temperature anomalies and the resulting climatic change in the low latitudes.…”

Section: Introductionmentioning

confidence: 97%

“…Because of the lack or highly simplified nature of atmospheric dynamics, the first two types of models do not allow to investigate the impact of Southern Ocean cooling on the ITCZ. The studies using coupled general circulation models did indeed find an impact of Southern Ocean cooling on low latitude climates (Ma & Wu, ) as well as changes in the characteristics of ENSO (Ma et al, ), but did not analyze the impact on the general atmospheric circulation in the tropics.…”

Section: Introductionmentioning

confidence: 99%

Response of the Intertropical Convergence Zone to Antarctic Ice Sheet Melt

Bakker

Prange

2018

Geophysical Research Letters

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Past cooling events in the Northern Hemisphere have been shown to impact the location of the intertropical convergence zone (ITCZ) and therewith induce a southward shift of tropical precipitation. Here we use high resolution coupled ocean‐atmosphere simulations to show that reasonable past melt rates of the Antarctic Ice Sheet can similarly have led to shifts of the ITCZ, albeit in opposite direction, through large‐scale surface air temperature changes over the Southern Ocean. Through sensitivity experiments employing slightly negative to large positive meltwater fluxes, we deduce that meridional shifts of the Hadley cell and therewith the ITCZ are, to a first order, a linear response to Southern Hemisphere high‐latitude surface air temperature changes and Antarctic Ice Sheet melt rates. This highlights the possibility to use past episodes of anomalous melt rates to better constrain a possible future response of low latitude precipitation to continued global warming and a shrinking Antarctic Ice Sheet.

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Impact of freshening over the Southern Ocean on ENSO

Cited by 8 publications

References 30 publications

Quantitative analysis of the feedback induced by the freshwater flux in the tropical Pacific using CMIP5

Quantitative analysis of the feedback induced by the freshwater flux in the tropical Pacific using CMIP5

Thermocline state change in the eastern equatorial Pacific during the late Pliocene/early Pleistocene intensification of Northern Hemisphere glaciation

Response of the Intertropical Convergence Zone to Antarctic Ice Sheet Melt

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