scholarly journals “El Niño Like” Hydroclimate Responses to Last Millennium Volcanic Eruptions

2016 ◽  
Vol 29 (8) ◽  
pp. 2907-2921 ◽  
Author(s):  
Samantha Stevenson ◽  
Bette Otto-Bliesner ◽  
John Fasullo ◽  
Esther Brady
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Temporal Structure ◽  
Volcanic Eruptions ◽  
Teleconnection Pattern ◽  
Last Millennium ◽  
Surface Cooling ◽  
Proxy Reconstructions ◽  
Neutral Conditions

Abstract The hydroclimate response to volcanic eruptions depends both on volcanically induced changes to the hydrologic cycle and on teleconnections with the El Niño–Southern Oscillation (ENSO), complicating the interpretation of offsets between proxy reconstructions and model output. Here, these effects are separated, using the Community Earth System Model Last Millennium Ensemble (CESM-LME), by examination of ensemble realizations with distinct posteruption ENSO responses. Hydroclimate anomalies in monsoon Asia and the western United States resemble the El Niño teleconnection pattern after “Tropical” and “Northern” eruptions, even when ENSO-neutral conditions are present. This pattern results from Northern Hemisphere (NH) surface cooling, which shifts the intertropical convergence zone equatorward, intensifies the NH subtropical jet, and suppresses the Southeast Asian monsoon. El Niño events following an eruption can then intensify the ENSO-neutral hydroclimate signature, and El Niño probability is enhanced two boreal winters following all eruption types. Additionally, the eruption-year ENSO response to eruptions is hemispherically dependent: the winter following a Northern eruption tends toward El Niño, while Southern volcanoes enhance the probability of La Niña events and Tropical eruptions have a very slight cooling effect. Overall, eruption-year hydroclimate anomalies in CESM disagree with the proxy record in both Southeast Asia and North America, suggesting that model monsoon representation cannot be solely responsible. Possible explanations include issues with the model ENSO response, the spatial or temporal structure of volcanic aerosol distribution, or data uncertainties.

No consistent ENSO response to volcanic forcing over the last millennium

Science ◽  
2020 ◽  
Vol 367 (6485) ◽  
pp. 1477-1481 ◽  
Author(s):  
Sylvia G. Dee ◽  
Kim M. Cobb ◽  
Julien Emile-Geay ◽  
Toby R. Ault ◽  
R. Lawrence Edwards ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Global Climate ◽  
Volcanic Eruptions ◽  
Explosive Volcanism ◽  
Forced Response ◽  
Last Millennium ◽  
Superposed Epoch Analysis ◽  
Volcanic Forcing

The El Niño–Southern Oscillation (ENSO) shapes global climate patterns yet its sensitivity to external climate forcing remains uncertain. Modeling studies suggest that ENSO is sensitive to sulfate aerosol forcing associated with explosive volcanism but observational support for this effect remains ambiguous. Here, we used absolutely dated fossil corals from the central tropical Pacific to gauge ENSO’s response to large volcanic eruptions of the last millennium. Superposed epoch analysis reveals a weak tendency for an El Niño–like response in the year after an eruption, but this response is not statistically significant, nor does it appear after the outsized 1257 Samalas eruption. Our results suggest that those models showing a strong ENSO response to volcanic forcing may overestimate the size of the forced response relative to natural ENSO variability.

scholarly journals Role of eruption season in reconciling model and proxy responses to tropical volcanism

2017 ◽  
Vol 114 (8) ◽  
pp. 1822-1826 ◽  
Author(s):  
Samantha Stevenson ◽  
John T. Fasullo ◽  
Bette L. Otto-Bliesner ◽  
Robert A. Tomas ◽  
Chaochao Gao
Keyword(s):  
El Niño ◽  
Climate Models ◽  
El Nino ◽  
Southern Oscillation ◽  
Volcanic Eruptions ◽  
Initial Response ◽  
La Niña ◽  
La Nina ◽  
Proxy Responses ◽  
Proxy Reconstructions

The response of the El Niño/Southern Oscillation (ENSO) to tropical volcanic eruptions has important worldwide implications, but remains poorly constrained. Paleoclimate records suggest an “El Niño-like” warming 1 year following major eruptions [Adams JB, Mann ME, Ammann CM (2003)Nature426:274–278] and “La Niña-like” cooling within the eruption year [Li J, et al. (2013)Nat Clim Chang3:822–826]. However, climate models currently cannot capture all these responses. Many eruption characteristics are poorly constrained, which may contribute to uncertainties in model solutions—for example, the season of eruption occurrence is often unknown and assigned arbitrarily. Here we isolate the effect of eruption season using experiments with the Community Earth System Model (CESM), varying the starting month of two large tropical eruptions. The eruption-year atmospheric circulation response is strongly seasonally dependent, with effects on European winter warming, the Intertropical Convergence Zone, and the southeast Asian monsoon. This creates substantial variations in eruption-year hydroclimate patterns, which do sometimes exhibit La Niña-like features as in the proxy record. However, eruption-year equatorial Pacific cooling is not driven by La Niña dynamics, but strictly by transient radiative cooling. In contrast, equatorial warming the following year occurs for all starting months and operates dynamically like El Niño. Proxy reconstructions confirm these results: eruption-year cooling is insignificant, whereas warming in the following year is more robust. This implies that accounting for the event season may be necessary to describe the initial response to volcanic eruptions and that climate models may be more accurately simulating volcanic influences than previously thought.

scholarly journals Assessing the impact of large volcanic eruptions of the Last Millennium on Australian rainfall regimes

2017 ◽  
Author(s):  
Stephanie Blake ◽  
Sophie C. Lewis ◽  
Allegra N. LeGrande
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Climate ◽  
Volcanic Eruptions ◽  
Explosive Volcanism ◽  
Climate Forcing ◽  
Last Millennium ◽  
Precipitation Anomalies ◽  
The Impact

Abstract. Explosive volcanism is an important natural climate forcing, impacting global surface temperatures and regional precipitation. Although previous studies have investigated aspects of the impact of tropical volcanism on various ocean-atmosphere systems and regional climate regimes, volcanic eruptions remain a poorly understood climate forcing and climatic responses are not well constrained. In this study, volcanic eruptions are explored in particular reference to Australian precipitation, and both the Indian Ocean Dipole (IOD) and El Nino-Southern Oscillation (ENSO). Using nine realisations of the Last Millennium (LM) with different time-evolving forcing combinations, from the NASA GISS ModelE2-R, the impact of the 6 largest tropical volcanic eruptions of this period are investigated. Overall, we find that volcanic aerosol forcing increased the likelihood of El Nino and positive IOD conditions for up to four years following an eruption, and resulted in positive precipitation anomalies over northwest (NW) and southeast (SE) Australia. Larger atmospheric sulfate loading coincides with more persistent positive IOD and El Nino conditions, enhanced positive precipitation anomalies over NW Australia, and dampened precipitation anomalies over SE Australia.

scholarly journals Response to Comment on “No consistent ENSO response to volcanic forcing over the last millennium”

Science ◽  
2020 ◽  
Vol 369 (6509) ◽  
pp. eabc1733
Author(s):  
Sylvia G. Dee ◽  
Kim M. Cobb ◽  
Julien Emile-Geay ◽  
Toby R. Ault ◽  
R. Lawrence Edwards ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Volcanic Eruptions ◽  
Dynamical Response ◽  
Last Millennium ◽  
Surface Cooling ◽  
Central Pacific ◽  
Volcanic Forcing ◽  
Large Volcanic Eruptions

Robock claims that our analysis fails to acknowledge that pan-tropical surface cooling caused by large volcanic eruptions may mask El Niño warming at our central Pacific site, potentially obscuring a volcano–El Niño connection suggested in previous studies. Although observational support for a dynamical response linking volcanic cooling to El Niño remains ambiguous, Robock raises some important questions about our study that we address here.

scholarly journals Assessing the impact of large volcanic eruptions of the last millennium (850–1850 CE) on Australian rainfall regimes

2018 ◽  
Vol 14 (6) ◽  
pp. 811-824 ◽  
Author(s):  
Stephanie A. P. Blake ◽  
Sophie C. Lewis ◽  
Allegra N. LeGrande ◽  
Ron L. Miller
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Volcanic Eruptions ◽  
Explosive Volcanism ◽  
Climate Forcing ◽  
Last Millennium ◽  
North West ◽  
Precipitation Anomalies ◽  
The Impact

Abstract. Explosive volcanism is an important natural climate forcing, impacting global surface temperatures and regional precipitation. Although previous studies have investigated aspects of the impact of tropical volcanism on various ocean–atmosphere systems and regional climate regimes, volcanic eruptions remain a poorly understood climate forcing and climatic responses are not well constrained. In this study, volcanic eruptions are explored in particular reference to Australian precipitation, and both the Indian Ocean Dipole (IOD) and El Niño–Southern Oscillation (ENSO). Using nine realisations of the last millennium (LM) (850–1850 CE) with different time-evolving forcing combinations, from the NASA GISS ModelE2-R, the impact of the six largest tropical volcanic eruptions of this period are investigated. Overall, we find that volcanic aerosol forcing increased the likelihood of El Niño and positive IOD conditions for up to four years following an eruption, and resulted in positive precipitation anomalies over north-west (NW) and south-east (SE) Australia. Larger atmospheric sulfate loading during larger volcanic eruptions coincided with more persistent positive IOD and El Niño conditions, enhanced positive precipitation anomalies over NW Australia, and dampened precipitation anomalies over SE Australia.

scholarly journals Impact of Strong Tropical Volcanic Eruptions on ENSO Simulated in a Coupled GCM

2013 ◽  
Vol 26 (14) ◽  
pp. 5169-5182 ◽  
Author(s):  
Masamichi Ohba ◽  
Hideo Shiogama ◽  
Tokuta Yokohata ◽  
Masahiro Watanabe
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Volcanic Eruptions ◽  
La Niña ◽  
Subsurface Water ◽  
Surface Cooling ◽  
La Nina ◽  
The Impact

Abstract The impact of strong tropical volcanic eruptions (SVEs) on the El Niño–Southern Oscillation (ENSO) and its phase dependency is investigated using a coupled general circulation model (CGCM). This paper investigates the response of ENSO to an idealized SVE forcing, producing a peak perturbation of global-mean surface shortwave radiation larger than −6.5 W m−2. Radiative forcing due to volcanic aerosols injected into the stratosphere induces tropical surface cooling around the volcanic forcing peak. Identical-twin forecast experiments of an ENSO-neutral year in response to an SVE forcing show an El Niño–like warming lagging one year behind the peak forcing. In addition to a reduced role of the mean subsurface water upwelling (known as the dynamical thermostat mechanism), the rapid land surface cooling around the Maritime Continent weakens the equatorial Walker circulation, contributing to the positive zonal gradient of sea surface temperature (SST) and precipitation anomalies over the equatorial Pacific. Since the warm and cold phases of ENSO exhibit significant asymmetry in their transition and duration, the impact of a SVE forcing on El Niño and La Niña is also investigated. In the warm phase of ENSO, the prediction skill of the SVE-forced experiments rapidly drops approximately six months after the volcanic peak. Since the SVE significantly facilitates the duration of El Niño, the following transition from warm to cold ENSO is disrupted. The impact of SVE forcing on La Niña is, however, relatively weak. These results imply that the intensity of a dynamical thermostat-like response to a SVE could be dependent on the phase of ENSO.

scholarly journals Tropical Temperature and Precipitation Responses to Large Volcanic Eruptions: Observations and AMIP5 Simulations

2016 ◽  
Vol 29 (4) ◽  
pp. 1325-1338 ◽  
Author(s):  
A. Meyer ◽  
D. Folini ◽  
U. Lohmann ◽  
T. Peter
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Surface Air Temperature ◽  
Volcanic Eruptions ◽  
Phase Correlation ◽  
Temperature And Precipitation ◽  
Precipitation Decrease ◽  
El Chichón ◽  
El Chichon

Abstract Tropical land mean surface air temperature and precipitation responses to the eruptions of El Chichón in 1982 and Pinatubo in 1991, as simulated by the atmosphere-only GCMs (AMIP) in phase 5 of the Coupled Model Intercomparison Project (CMIP5), are examined and compared to three observational datasets. The El Niño–Southern Oscillation (ENSO) signal was statistically separated from the volcanic signal in all time series. Focusing on the ENSO signal, it was found that the 17 investigated AMIP models successfully simulate the observed 4-month delay in the temperature responses to the ENSO phase but simulate somewhat too-fast precipitation responses during the El Niño onset stage. The observed correlation between temperature and ENSO phase (correlation coefficient of 0.75) is generally captured well by the models (simulated correlation of 0.71 and ensemble means of 0.61–0.83). For precipitation, mean correlations with the ENSO phase are −0.59 for observations and −0.53 for the models, with individual ensemble members having correlations as low as −0.26. Observed, ENSO-removed tropical land temperature and precipitation decrease by about 0.35 K and 0.25 mm day−1 after the Pinatubo eruption, while no significant decrease in either variable was observed after El Chichón. The AMIP models generally capture this behavior despite a tendency to overestimate the precipitation response to El Chichón. Scatter is substantial, both across models and across ensemble members of individual models. Natural variability thus may still play a prominent role despite the strong volcanic forcing.

scholarly journals Simulated enhancement of ENSO-related rainfall variability due to Australian dust

2011 ◽  
Vol 11 (1) ◽  
pp. 1595-1639 ◽  
Author(s):  
L. D. Rotstayn ◽  
M. A. Collier ◽  
R. M. Mitchell ◽  
Y. Qin ◽  
S. K. Campbell
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
La Niña ◽  
Climate Feedback ◽  
Surface Cooling ◽  
Atmospheric Heating ◽  
La Nina ◽  
Eastern Australia

Abstract. Average dust emissions from Australia are small compared to those from the major sources in the Northern Hemisphere. However, they are highly episodic, and this may increase the importance of Australian dust as a climate feedback agent. We compare two 160-year coupled atmosphere-ocean simulations of modern-day climate using the CSIRO Mark 3.6 global climate model (GCM). The first run (DUST) includes an interactive treatment of mineral dust and its direct radiative effects. The second run (NODUST) is otherwise identical, but has the Australian dust source set to zero. We focus on the austral spring season, when the correlation between rainfall and the El Niño Southern Oscillation (ENSO) is strongest over Australia. We find that the ENSO-rainfall relationship over eastern Australia is stronger in the DUST run: dry (El Niño) years tend to be drier, and wet (La Niña) years wetter. The ENSO-rainfall relationship is also weaker over north-western Australia in the DUST run. The amplification of ENSO-related rainfall variability over eastern Australia and the weaker ENSO-rainfall relationship over the north-west both represent an improvement relative to observations. The suggested mechanism over eastern Australia involves stabilisation of the surface layer due to enhanced atmospheric heating and surface cooling in El Niño years, and enhanced ascent and moisture convergence driven by atmospheric heating in La Niña years. The results suggest that (1) a realistic treatment of Australian dust may be necessary for accurate simulation of the ENSO-rainfall relationship over Australia, and (2) radiative feedbacks involving dust may be important for understanding natural rainfall variability over Australia.

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