The Recent Strengthening of Walker Circulation

Choi, Jae‐Kap; Kim, In-Gyum; Kim, Jeoung-Yun; Park, Cheol-Hong

doi:10.2151/sola.2016-022

Cited by 11 publications

(11 citation statements)

References 23 publications

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“…42 43 Keywords: Decadal climate variability, Pacific Ocean, global warming, ocean heat content, 44 air-sea interactions 45 low-frequency tail of ENSO variations is associated with decadal-scale SST anomalies in the 71 tropical Pacific, and the associated global SST pattern is called the Interdecadal Pacific 72Oscillation (IPO; Zhang et al, 1997; Power et al, 1999). 73The IPO shifted from a warm to a cold phase around 1998, yielding a cooling trend of 74 central and eastern Pacific SST, associated with an unprecedented intensification of the 75 Pacific Walker circulation (Kociuba and Power, 2015;Choi et al, 2016) and strengthening of 76 setup results in more realistic global SST patterns due to the remote impacts of Pacific SST 96 anomalies through teleconnections, and a reduced rate of global surface temperature warming 97 over the last two decades (e.g. Kosaka and Xie, 2013).…”

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confidence: 99%

“…The IPO shifted from a warm to a cold phase around 1998, yielding a cooling trend of 74 central and eastern Pacific SST, associated with an unprecedented intensification of the 75 Pacific Walker circulation (Kociuba and Power, 2015;Choi et al, 2016) and strengthening of 76 setup results in more realistic global SST patterns due to the remote impacts of Pacific SST 96 anomalies through teleconnections, and a reduced rate of global surface temperature warming 97 over the last two decades (e.g. Kosaka and Xie, 2013).…”

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Global ocean heat content redistribution during the 1998–2012 Interdecadal Pacific Oscillation negative phase

et al. 2018

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23Previous studies have linked the slowdown in global surface temperature warming 24 since 2000 to a negative Interdecadal Pacific Oscillation (IPO) phase. Here, we investigate the 25 changes in ocean heat content (OHC) during this period. We compare two ensembles of 26 coupled model experiments with either zero or observed prescribed tropical Pacific wind 27 stress interannual anomalies. This successfully constrains the global surface temperature, sea 28 level pressure and OHC patterns associated with the IPO phase transition around 1998. The 29 negative IPO phase (1998 to 2012) is associated with a global ocean heat redistribution. The 30 anomalously cold tropical Pacific Ocean leads to an increased oceanic uptake in this region, 31 and a global OHC increase of 4x10 22 J. The cold equatorial Pacific also forces mid-latitude 32 wind changes through atmospheric teleconnections, leading to an enhanced wind-driven heat 33 transport convergence at 40°N and 40°S. Enhanced Pacific easterlies also yield an enhanced 34 heat transport to the Indian Ocean via the Indonesian throughflow. As a result, the anomalous 35Pacific heat uptake is entirely exported towards the North Pacific (~50%), Indian (~30%) and 36 Southern (~20%) Oceans. A significant fraction of this heat is released back to the 37 atmosphere in the North Pacific and Indian basins, and transported across 31°S in the Indian 38Ocean. Overall, OHC increases most in the Southern Ocean (~60% of global changes) and 39 northern Pacific (~40%), with negligible changes in the Indian and Atlantic basins. These 40 results point to the major importance of oceanic circulation in re-distributing the Pacific heat 41 uptake globally during negative IPO phases. 42 43 Keywords: Decadal climate variability, Pacific Ocean, global warming, ocean heat content, 44 air-sea interactions 45 low-frequency tail of ENSO variations is associated with decadal-scale SST anomalies in the 71 tropical Pacific, and the associated global SST pattern is called the Interdecadal Pacific 72Oscillation (IPO; Zhang et al., 1997; Power et al., 1999). 73The IPO shifted from a warm to a cold phase around 1998, yielding a cooling trend of 74 central and eastern Pacific SST, associated with an unprecedented intensification of the 75 Pacific Walker circulation (Kociuba and Power, 2015;Choi et al., 2016) and strengthening of 76 setup results in more realistic global SST patterns due to the remote impacts of Pacific SST 96 anomalies through teleconnections, and a reduced rate of global surface temperature warming 97 over the last two decades (e.g. Kosaka and Xie, 2013). 98 A burning question is thus: where did the extra heat pumped into the Pacific during the 99 hiatus decade go? This question is not easy to tackle from observations alone. Deep ocean 100 observations are indeed too sparse to track the OHC changes, even with improved recent 101 estimates (Cheng et al., 2017). The deployment of Argo floats in the early 2000s greatly 102 improved the sampling (Lyman, 2012; Abraham et al., 2013), but the current ...

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Global ocean heat content redistribution during the 1998–2012 Interdecadal Pacific Oscillation negative phase

et al. 2018

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“…Different from the traditional El Niño that is strongly associated with thermocline variations, the CP El Niño appears more related to zonal advection and atmospheric forcing (3,(8)(9)(10)(11). Particularly, along with the increasing occurrence of the CP El Niño since the 1990s, a recent multidecadal acceleration of easterly trade winds has been observed (12)(13)(14), which is linked to the strengthening of the Walker circulation (15)(16)(17). In addition to the distinct climate patterns in the equatorial Pacific region, the ENSO diversity also has strong impact on global climate and seasonal prediction through teleconnections (4,18) and is suggested as a possible link to climate change (19).…”

Section: Then a Three-state Stochastic Markov Jump Process Is Used Tomentioning

confidence: 99%

Simple stochastic dynamical models capturing the statistical diversity of El Niño Southern Oscillation

Chen

Majda

2017

Proc. Natl. Acad. Sci. U.S.A.

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The El Niño Southern Oscillation (ENSO) has significant impact on global climate and seasonal prediction. A simple modeling framework is developed here that automatically captures the statistical diversity of ENSO. First, a stochastic parameterization of the wind bursts including both westerly and easterly winds is coupled to a simple ocean-atmosphere model that is otherwise deterministic, linear, and stable. Second, a simple nonlinear zonal advection with no ad hoc parameterization of the background sea-surface temperature (SST) gradient and a mean easterly trade wind anomaly representing the multidecadal acceleration of the trade wind are both incorporated into the coupled model that enables anomalous warm SST in the central Pacific. Then a three-state stochastic Markov jump process is used to drive the wind burst activity that depends on the strength of the western Pacific warm pool in a simple and effective fashion. It allows the coupled model to simulate the quasi-regular moderate traditional El Niño, the super El Niño, and the central Pacific (CP) El Niño as well as the La Niña with realistic features. In addition to the anomalous SST, the Walker circulation anomalies at different ENSO phases all resemble those in nature. In particular, the coupled model succeeds in reproducing the observed episode during the 1990s, where a series of 5-y CP El Niños is followed by a super El Niño and then a La Niña. Importantly, both the variance and the non-Gaussian statistical features in different Niño regions spanning from the western to the eastern Pacific are captured by the coupled model.

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“…1c), associated with an intensification of Pacific trade winds and with a shoaling of the thermocline in the Eastern Equatorial Pacific (e.g. Balmaseda et al 2013;de Boisséson et al 2014;England et al 2014; Kociuba and Power 2015;Choi et al 2016;Gastineau et al, 2018). Poleward propagating coastal waves and a shoaling of the nearshore thermocline may also play a key role in modulating SST at decadal time scales off-Chile (e.g.…”

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Contributions of Internal Variability and External Forcing to the Recent Trends in the Southeastern Pacific and Peru–Chile Upwelling System

et al. 2020

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In a warming world context, Sea Surface Temperature (SST) off central-south Peru, northern Chile and further offshore increases at a slower rate than the global average since several decades, i.e. cools, relative to the global average. This tendency is synchronous with an Interdecadal Pacific Oscillation (IPO) negative trend since ∼1980, which has a cooling signature in the southeastern Pacific. Here, we use a large ensemble of historical coupled model simulations to investigate the relative roles of internal variability (and in particular the IPO) and external forcing in driving this relative regional cooling, and the associated mechanisms. The ensemble-mean reproduces the relative cooling, in response to an externally-forced southerly wind anomaly, which strengthens the upwelling off Chile in recent decades. This southerly wind anomaly results from the poleward expansion of the Southern Hemisphere Hadley Cell. Attribution experiments reveal that this poleward expansion and the resulting enhanced upwelling mostly occur in response to increasing greenhouse gases and stratospheric ozone depletion since ∼1980. An oceanic heat budget confirms that the wind-forced upwelling enhancement dominates the relative cooling near the coast. In contrast, a wind-forced deepening of the mixed layer drives the offshore cooling. While internal variability contributes to the spread of tendencies, the ensemble-mean relative cooling in the southeastern Pacific is consistent with observations and occurs irrespectively of the IPO phase, hence indicating the preeminent role of external forcing.

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The Recent Strengthening of Walker Circulation

Abstract: This study calculated the Walker circulation index and then discovered strengthening of the circulation

Cited by 11 publications

References 23 publications

Global ocean heat content redistribution during the 1998–2012 Interdecadal Pacific Oscillation negative phase

Global ocean heat content redistribution during the 1998–2012 Interdecadal Pacific Oscillation negative phase

Simple stochastic dynamical models capturing the statistical diversity of El Niño Southern Oscillation

Contributions of Internal Variability and External Forcing to the Recent Trends in the Southeastern Pacific and Peru–Chile Upwelling System

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