Impact of Multiscale Variability on Last 6,000 Years Indian and West African Monsoon Rain

Braconnot, Pascale; Crétat, Julien; Marti, Olivier; Balkanski, Yves; Caubel, Arnaud; Cozic, Anne; Foujols, Marie-Alice; Sanogo, Sidiki

doi:10.1029/2019gl084797

Cited by 25 publications

(26 citation statements)

References 34 publications

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“…x10 6 ability (see also Appendix B, Figure 13). This last result supports recent work showing that the internal variability of the climate system from the mid-Holocene to present times can mask any long-term trend for periods up to about 500 years (Braconnot et al, 2019a).…”

Section: The Indo-pacific As a High-dimensional Dynamical Systemsupporting

confidence: 90%

Climate change in the Indo-Pacific basin from mid- to late Holocene

Falasca

Crétat

Bracco

et al. 2021

Preprint

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Changes in climate mean state profoundly impact climate variability. Here, we quantify slow changes in the mean climate induced by the variations in the Earth’s orbit from mid- to late Holocene, and their feedback on the main modes of climate variability. We focus on the Indo-Pacific system and show that mid-Holocene conditions favored the dominance of an equatorial dipole mode in the Indian Ocean (IO), independent of the El Niño Southern Oscillation (ENSO) and different from the IO Dipole (IOD) observed today. Mean state changes induced a gradual shift to an IO basin mode that along with the IOD modulates most of the IO variance at present. The climate modes evolution and their connectivity changes are investigated over 6,000 years using a complex network methodology and principal component analysis. To characterize the nature of this transition, we explore the trajectory of the Indo-Pacific climate by accounting for its spatiotemporal and multivariable dependency. The full trajectory of the system is explored from a dynamical system perspective by constructing a state space representation. The manifold embedded in the 104 -dimensional state space provides a compact representation of the system evolution and points to a gradual shift of the basin of attractions in the tropics. This approach, together with a mean state analysis, reveals that a strengthening of the Walker circulation set the stage for a shift in modes in both basins.

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Section: The Indo-pacific As a High-dimensional Dynamical Systemsupporting

confidence: 90%

Climate change in the Indo-Pacific basin from mid- to late Holocene

Falasca

Crétat

Bracco

et al. 2021

Preprint

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show abstract

“…For example, transient simulations for part or the whole Holocene period using an intermediate ocean-atmosphere coupled model of the tropical Pacific climate forced by the orbital forcing (Clement et al, 2000), a fully coupled general circulation model with the time-varying climate forcing including orbital, greenhouse gas, meltwater flux, and continental ice sheets (Liu et al, 2014), and a hybrid-type simulation using a combination of the intermediate complexity of earth system model forced orbital forcing and intermediate coupled tropical pacific climate model with varying background state , all showed a significant reduction of ENSO intensity during mid-Holocene and its recovery to modern-day ENSO strength around the late Holocene. A study with another set of transient Holocene simulations with coupled climate models confirmed this result, but found that it was the result of chaotic processes (Braconnot et al, 2019).…”

Section: Introductionmentioning

confidence: 79%

“…shallower and stronger thermocline in the equatorial Pacific (An et al, 2008), which enhances the ocean-atmosphere coupling and amplifies the ENSO variability (Zhang et al, 2008). A gradually intensified ENSO from mid-to late Holocene also appears in a long-transient simulation since the last 21,000 years (Liu et al, 2014) and of the last 6000 years (Braconnot et al, 2019). For the equilibrium response to global warming, the subsurface ocean will eventually warm up and reduce the vertical temperature gradient and weaken the ENSO variability.…”

Section: Mechanisms and Discussionmentioning

confidence: 99%

Comparison of past and future simulations of ENSO in CMIP5/PMIP3 and CMIP6/PMIP4 models

Brown¹,

Brierley²,

An³

et al. 2020

Preprint

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Abstract. El Niño-Southern Oscillation (ENSO) is the strongest mode of interannual climate variability in the current climate, influencing ecosystems, agriculture and weather systems across the globe, but future projections of ENSO frequency and amplitude remain highly uncertain. A comparison of changes in ENSO in a range of past and future climate simulations can provide insights into the sensitivity of ENSO to changes in the mean state, including changes in the seasonality of incoming solar radiation, global average temperatures and spatial patterns of sea surface temperatures. As a comprehensive set of coupled model simulations are now available for both palaeoclimate time-slices (the Last Glacial Maximum, mid-Holocene and Last Interglacial) and idealised future warming scenarios (one percent per year CO2 increase, abrupt four times CO2 increase), this allows a detailed evaluation of ENSO changes in this wide range of climates. Such a comparison can assist in constraining uncertainty in future projections, providing insights into model agreement and the sensitivity of ENSO to a range of factors. The majority of models simulate a consistent weakening of ENSO activity in the Last Interglacial and mid-Holocene experiments, and there is an ensemble mean reduction of variability in the western equatorial Pacific in the Last Glacial Maximum experiments. Changes in global temperature produce a weaker precipitation response to ENSO in the cold Last Glacial Maximum experiments, and an enhanced precipitation response to ENSO in the warm increased CO2 experiments. No consistent relationship between changes in ENSO amplitude and annual cycle was identified across experiments.

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“…For example, transient simulations for part of or the whole Holocene period using an intermediate oceanatmosphere coupled model of the tropical Pacific climate forced by the orbital forcing (Clement et al, 2000), a fully coupled general circulation model with the time-varying climate forcing including orbital, greenhouse gas, meltwater flux, and continental ice sheets (Liu et al, 2014), and a hybrid-type simulation using a combination of the intermediate complexity of Earth-system-model-forced orbital forcing and intermediate coupled tropical Pacific climate model with varying background state all showed a significant reduction of ENSO intensity during mid-Holocene and its recovery to modern-day ENSO strength around the late Holocene. A study with another set of transient Holocene simulations with coupled climate models confirmed this result but found that it was the result of chaotic processes (Braconnot et al, 2019).…”

Section: Introductionmentioning

confidence: 82%

“…During the transient period of global warming, the tropical SSTs warm much faster than the subsurface ocean and leads to a shallower and stronger thermocline in the equatorial Pacific (An et al, 2008), which enhances the ocean-atmosphere coupling and amplifies the ENSO variability (Zhang et al, 2008). A gradually intensified ENSO from the mid-Holocene to late Holocene also appears in a long-transient simulation since the last 21 000 years (Liu et al, 2014) and of the last 6000 years (Braconnot et al, 2019). For the equilibrium response to global warming, the subsurface ocean will eventually warm up and reduce the vertical temperature gradient and weaken the ENSO variability.…”

Section: Mechanisms and Discussionmentioning

confidence: 99%

Comparison of past and future simulations of ENSO in CMIP5/PMIP3 and CMIP6/PMIP4 models

Brown

Brierley

et al. 2020

Clim. Past

View full text Add to dashboard Cite

Abstract. El Niño–Southern Oscillation (ENSO) is the strongest mode of interannual climate variability in the current climate, influencing ecosystems, agriculture, and weather systems across the globe, but future projections of ENSO frequency and amplitude remain highly uncertain. A comparison of changes in ENSO in a range of past and future climate simulations can provide insights into the sensitivity of ENSO to changes in the mean state, including changes in the seasonality of incoming solar radiation, global average temperatures, and spatial patterns of sea surface temperatures. As a comprehensive set of coupled model simulations is now available for both palaeoclimate time slices (the Last Glacial Maximum, mid-Holocene, and last interglacial) and idealised future warming scenarios (1 % per year CO2 increase, abrupt four-time CO2 increase), this allows a detailed evaluation of ENSO changes in this wide range of climates. Such a comparison can assist in constraining uncertainty in future projections, providing insights into model agreement and the sensitivity of ENSO to a range of factors. The majority of models simulate a consistent weakening of ENSO activity in the last interglacial and mid-Holocene experiments, and there is an ensemble mean reduction of variability in the western equatorial Pacific in the Last Glacial Maximum experiments. Changes in global temperature produce a weaker precipitation response to ENSO in the cold Last Glacial Maximum experiments and an enhanced precipitation response to ENSO in the warm increased CO2 experiments. No consistent relationship between changes in ENSO amplitude and annual cycle was identified across experiments.

show abstract

Impact of Multiscale Variability on Last 6,000 Years Indian and West African Monsoon Rain

Cited by 25 publications

References 34 publications

Climate change in the Indo-Pacific basin from mid- to late Holocene

Climate change in the Indo-Pacific basin from mid- to late Holocene

Comparison of past and future simulations of ENSO in CMIP5/PMIP3 and CMIP6/PMIP4 models

Comparison of past and future simulations of ENSO in CMIP5/PMIP3 and CMIP6/PMIP4 models

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