A Subsurface Indian Ocean Dipole Response to Tropical Volcanic Eruptions

Izumo, Takeshi; Khodri, Myriam; Lengaigne, Matthieu; Suresh, Iyyappan

doi:10.1029/2018gl078515

Cited by 11 publications

(10 citation statements)

References 59 publications

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“…A different possibility is that Africa cools more than the Indian Ocean which intensifies westerlies across the basin and strengthens the zonal SST gradient. Over interannual timescales, Plinean eruptions are capable of altering the Indian Ocean Walker circulation and zonal SST gradient by changing land‐sea temperature gradients between Africa and the Indian Ocean, resulting in an nIOD‐like state in simulations (Izumo et al., 2018). This leads to reduced rainfall over tropical East Africa similar to what is reconstructed through HS‐1.…”

Section: Discussionmentioning

confidence: 99%

Zonal Indian Ocean Variability Drives Millennial‐Scale Precipitation Changes in Northern Madagascar

Tiger,

Burns,

Dawson

et al. 2023

Paleoceanog and Paleoclimatol

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The low latitude Indian Ocean is warming faster than other tropical basins, and its interannual climate variability is projected to become more extreme under future emissions scenarios with substantial impacts on developing Indian Ocean rim countries. Therefore, it has become increasingly important to understand the drivers of regional precipitation in a changing climate. Here we present a new speleothem record from Anjohibe, a cave in northwest (NW) Madagascar well situated to record past changes in the Intertropical Convergence Zone (ITCZ). U‐Th ages date speleothem growth from 27 to 14 ka. δ18O, δ13C, and trace metal proxies reconstruct drier conditions during Heinrich Stadials 1 and 2, and wetter conditions during the Last Glacial Maximum and Bølling–Allerød. This is surprising considering hypotheses arguing for southward (northward) ITCZ shifts during North Atlantic cooling (warming) events, which would be expected to result in wetter (drier) conditions at Anjohibe in the Southern Hemisphere tropics. The reconstructed Indian Ocean zonal (west‐east) sea surface temperature (SST) gradient is in close agreement with hydroclimate proxies in NW Madagascar, with periods of increased precipitation correlating with relatively warmer conditions in the western Indian Ocean and cooler conditions in the eastern Indian Ocean. Such gradients could drive long‐term shifts in the strength of the Walker circulation with widespread effects on hydroclimate across East Africa. These results suggest that during abrupt millennial‐scale climate changes, it is not meridional ITCZ shifts, but the tropical Indian Ocean SST gradient and Walker circulation driving East African hydroclimate variability.

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Section: Discussionmentioning

confidence: 99%

Zonal Indian Ocean Variability Drives Millennial‐Scale Precipitation Changes in Northern Madagascar

Tiger,

Burns,

Dawson

et al. 2023

Paleoceanog and Paleoclimatol

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“…Figure 8 shows the response of the DMI to large volcanic eruptions and shows that periods in which large volcanic eruptions occur (denoted by grey bars) normally coincide with local maximum or minimum DMI values. Previous studies show that volcanic eruptions increase the likelihood of positive IOD events occurring in the following year (Maher et al, 2015) and that tropical volcanic eruptions can induce a negative IOD in the year of an eruption (Izumo et al, 2018). However, Figure 8 shows that phase responses of the IOD following large volcanic eruptions remain unclear even from models showing significant connections between VRF and the DMI.…”

Section: Resultsmentioning

confidence: 99%

“…Few efforts (e.g. Izumo et al, 2018; Maher et al, 2015; Zheng et al, 2013) have been made to quantify the IOD responses to external forcings. Studies have used select model and CMIP5 historical simulations (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Studies have used select model and CMIP5 historical simulations (i.e. 1850–2005) to show that volcanic forcing increases the likelihood of a positive IOD emerging from eruptions of the following year (Maher et al, 2015) while tropical volcanic eruptions create a subsurface ocean response similar to a negative IOD in the year of an eruption (Izumo et al, 2018). Increase in concentrations GHGs induces an IOD-like warming pattern in the tropical Indian Ocean but does not alter the interannual variance of the IOD (Zheng et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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The Indian Ocean Dipole response to external forcing in the coupled model intercomparison project phase 5 simulations of the last millennium

Bae

2021

The Holocene

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The Indian Ocean Dipole (IOD) is a major mode of interannual climate variability, but its response to external climate forcings (i.e. solar forcing, volcanic radiative forcing (VRF) and greenhouse gas (GHG) radiative forcing) remains elusive. To improve our understanding of the variability of the IOD, it is necessary to investigate the IOD’s response to external forcings through multi-model simulations. Here a Granger causality test is used to examine the impact of external forcings on the IOD from past 1000 years simulations (850–1850 Common Era) derived from Coupled Model Intercomparison Project Phase 5 (CMIP5) models. The results show significant causal effects of VRF on the IOD in preindustrial times of the past 1000 years from the MPI-ESM-P, MRI-CGCM3, GISS-E2-R and CCSM4 models and uncertainties in the IOD’s responses to volcanic eruptions from other six models. Additionally, the phase responses (i.e. positive or negative) of the IOD to large volcanic eruptions remain unclear even from models showing significant causal impacts of VRF on the IOD. This result shows that the IOD exhibits a more complex response to volcanic forcing than the El Niño-Southern Oscillation. The causal impact of solar forcing on the IOD is more likely to be weak in most models. The IOD’s response to GHG variations is not significant across all the models due to minor fluctuations in GHGs occurring during preindustrial times of the past 1000 years. Further analyses based on new, improved and higher resolution models might further our understanding of the IOD’s responses to external forcing.

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“…RSST has to date mostly been used in the global warming context, for instance, to understand the spatial patterns of changes in tropical cyclones (as aforementioned), in the hydrological cycle (e.g., Xie et al, ), and to define ENSO events (Williams & Patricola, ) and their convective signature (Johnson & Kosaka, ) in a warming world. RSST also allows isolating the ENSO and IOD signals in the context of global cooling induced by tropical explosive volcanic eruptions (Izumo et al, ; Khodri et al, ). RSST is finally useful for characterizing the influence of the equatorial Pacific bias in climate models on the Walker circulation and on ENSO (Bayr et al, , , b).…”

Section: Introductionmentioning

confidence: 99%

Relevance of Relative Sea Surface Temperature for Tropical Rainfall Interannual Variability

Izumo

Vialard

Lengaigne

et al. 2020

Geophysical Research Letters

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The coupling between sea surface temperature (SST) anomalies and rainfall is an important driver of tropical climate variability. Observations however reveal inconsistencies, such as decreased convective rainfall in regions with positive SST anomalies in the tropical Indian and Atlantic Oceans during and after El Niño–Southern Oscillation (ENSO) events. The upper troposphere warms during El Niño events, stabilizing the atmosphere. SST anomalies only account for the influence of the surface. Using theoretical arguments, we show that relative SST (RSST; defined as SST minus its tropical mean) anomalies, by also accounting for the influence of upper tropospheric temperature anomalies on gross moist stability, explain tropical convection interannual variations better than SST anomalies in observations and climate models. This relation further improves when RSST anomalies are weighted by the precipitation climatology to account for low and high‐precipitation regimes. Using RSST is thus essential to understand El Niño–Southern Oscillation teleconnections and interactions between modes of tropical climate variability.

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A Subsurface Indian Ocean Dipole Response to Tropical Volcanic Eruptions

Cited by 11 publications

References 59 publications

Zonal Indian Ocean Variability Drives Millennial‐Scale Precipitation Changes in Northern Madagascar

Zonal Indian Ocean Variability Drives Millennial‐Scale Precipitation Changes in Northern Madagascar

The Indian Ocean Dipole response to external forcing in the coupled model intercomparison project phase 5 simulations of the last millennium

Relevance of Relative Sea Surface Temperature for Tropical Rainfall Interannual Variability

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