scholarly journals How Do Volcanic Eruptions Influence Decadal Megadroughts over Eastern China?

2020 ◽  
Vol 33 (19) ◽  
pp. 8195-8207 ◽  
Author(s):  
Liang Ning ◽  
Kefan Chen ◽  
Jian Liu ◽  
Zhengyu Liu ◽  
Mi Yan ◽  
...  
Keyword(s):  
Asian Summer Monsoon ◽  
Eastern China ◽  
Volcanic Eruptions ◽  
Internal Variability ◽  
Last Millennium ◽  
Decadal Scale ◽  
Community Earth System Model ◽  
Sea Surface Temperature Anomalies ◽  
Asian Summer ◽  
The Western Pacific

AbstractThe influence and mechanism of volcanic eruptions on decadal megadroughts over eastern China during the last millennium were investigated using a control (CTRL) and five volcanic eruption sensitivity experiments (VOLC) from the Community Earth System Model (CESM) Last Millennium Ensemble (LME) archive. The decadal megadroughts associated with the failures of the East Asian summer monsoon (EASM) are associated with a meridional tripole of sea surface temperature anomalies (SSTAs) in the western Pacific from the equator to high latitudes, suggestive of a decadal-scale internal mode of variability that emerges from empirical orthogonal function (EOF) analysis. Composite analyses further showed that, on interannual time scales, within a decade after an eruption the megadrought was first enhanced but then weakened, due to the change from an El Niño state to a La Niña state. The impacts of volcanic eruptions on the magnitudes of megadroughts are superposed on internal variability. Therefore, the evolution of decadal megadroughts coinciding with strong volcanic eruptions demonstrate that the impacts of internal variability and external forcing can combine to influence hydroclimate.

scholarly journals Modeling of severe persistent droughts over eastern China during the last millennium

2014 ◽  
Vol 10 (3) ◽  
pp. 1079-1091 ◽  
Author(s):  
Y. Peng ◽  
C. Shen ◽  
H. Cheng ◽  
Y. Xu
Keyword(s):  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
Eastern China ◽  
Volcanic Eruptions ◽  
Internal Variability ◽  
Last Millennium ◽  
Proxy Data ◽  
Monsoon Variability ◽  
Primary Driver ◽  
Climate Forcings

Abstract. We use proxy data and modeled data from 1000 year model simulations with a variety of climate forcings to examine the occurrence of severe event of persistent drought over eastern China during the last millennium and diagnose the mechanisms. Results show that the model was able to roughly simulate most of these droughts over the study area during the last millennium such as those that occurred during the periods of 1123–1152, 1197–1223, 1353–1363, 1428–1449, 1479–1513, and 1632–1645. Our analyses suggest that these six well-captured droughts may caused by the East Asian summer monsoon (EASM) weakening. Study on the wavelet transform and spectral analysis reveals these events occurred all at the statistically significant 15–35-year timescale. A modeled data intercomparison suggests the possibility that solar activity may be the primary driver in the occurrence of the 1129–1144, 1354–1365, 1466–1491 and 1631–1648 droughts as identified by the model. However another possibility that these events may be related to internal variability cannot be excluded. Although the El Niño–Southern Oscillation (ENSO) plays an important role in monsoon variability, a temporally consistent relationship between the droughts and SST pattern in the Pacific Ocean could not be found either in the modeled or proxy data. Our analyses also indicate that large volcanic eruptions play a role as an amplifier in the drought of 1631–1648 and caused the droughts of 1830–1853 and 1958–1976, which was identified by the model.

scholarly journals Climate and carbon cycle dynamics in a CESM simulation from 850 to 2100 CE

2015 ◽  
Vol 6 (2) ◽  
pp. 411-434 ◽  
Author(s):  
F. Lehner ◽  
F. Joos ◽  
C. C. Raible ◽  
J. Mignot ◽  
A. Born ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Volcanic Eruptions ◽  
Internal Variability ◽  
Total Solar Irradiance ◽  
Last Millennium ◽  
Time Period ◽  
Decadal Scale ◽  
Current Century ◽  
Community Earth System Model ◽  
Ocean Carbon

Abstract. Under the protocols of phase 3 of the Paleoclimate Modelling Intercomparison Project, a number of simulations were produced that provide a range of potential climate evolutions from the last millennium to the end of the current century. Here, we present the first simulation with the Community Earth System Model (CESM), which includes an interactive carbon cycle, that covers the last millennium. The simulation is continued to the end of the twenty-first century. Besides state-of-the-art forcing reconstructions, we apply a modified reconstruction of total solar irradiance to shed light on the issue of forcing uncertainty in the context of the last millennium. Nevertheless, we find that structural uncertainties between different models can still dominate over forcing uncertainty for quantities such as hemispheric temperatures or the land and ocean carbon cycle response. Compared to other model simulations, we find forced decadal-scale variability to occur mainly after volcanic eruptions, while during other periods internal variability masks potentially forced signals and calls for larger ensembles in paleoclimate modeling studies. At the same time, we were not able to attribute millennial temperature trends to orbital forcing, as has been suggested recently. The climate–carbon-cycle sensitivity in CESM during the last millennium is estimated to be between 1.0 and 2.1 ppm °C−1. However, the dependence of this sensitivity on the exact time period and scale illustrates the prevailing challenge of deriving robust constraints on this quantity from paleoclimate proxies. In particular, the response of the land carbon cycle to volcanic forcing shows fundamental differences between different models. In CESM the tropical land dictates the response to volcanoes, with a distinct behavior for large and moderate eruptions. Under anthropogenic emissions, global land and ocean carbon uptake rates emerge from the envelope of interannual natural variability by about year 1947 and 1877, respectively, as simulated for the last millennium.

scholarly journals Climate and carbon cycle dynamics in a CESM simulation from 850–2100 CE

2015 ◽  
Vol 6 (1) ◽  
pp. 351-406 ◽  
Author(s):  
F. Lehner ◽  
F. Joos ◽  
C. C. Raible ◽  
J. Mignot ◽  
A. Born ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Volcanic Eruptions ◽  
Internal Variability ◽  
Total Solar Irradiance ◽  
Historical Period ◽  
Last Millennium ◽  
Coupled Modelling ◽  
Decadal Scale ◽  
Current Century ◽  
Ocean Carbon

Abstract. Under the protocols of the Paleoclimate and Coupled Modelling Intercomparison Projects a number of simulations were produced that provide a range of potential climate evolutions from the last millennium to the end of the current century. Here, we present the first simulation with the Community Earth System Model (CESM), which includes an interactive carbon cycle, that continuously covers the last millennium, the historical period, and the twenty-first century. Besides state-of-the-art forcing reconstructions, we apply a modified reconstruction of total solar irradiance to shed light on the issue of forcing uncertainty in the context of the last millennium. Nevertheless, we find that structural uncertainties between different models can still dominate over forcing uncertainty for quantities such as hemispheric temperatures or the land and ocean carbon cycle response. Comparing with other model simulations we find forced decadal-scale variability to occur mainly after volcanic eruptions, while during other periods internal variability masks potentially forced signals and calls for larger ensembles in paleoclimate modeling studies. At the same time, we fail to attribute millennial temperature trends to orbital forcing, as has been suggested recently. The climate-carbon cycle sensitivity in CESM during the last millennium is estimated to be about 1.3 ppm °C−1. However, the dependence of this sensitivity on the exact time period and scale illustrates the prevailing challenge of deriving robust constrains on this quantity from paleoclimate proxies. In particular, the response of the land carbon cycle to volcanic forcing shows fundamental differences between different models. In CESM the tropical land dictates the response to volcanoes with a distinct behavior for large and moderate eruptions. Under anthropogenic emissions, global land and ocean carbon uptake rates emerge from the envelope of interannual natural variability as simulated for the last millennium by about year 1947 and 1877, respectively.

scholarly journals Timescale-dependence of the relationship between the East Asian summer monsoon strength and precipitation over eastern China in the last millennium

2017 ◽  
Author(s):  
Jian Shi ◽  
Qing Yan ◽  
Huijun Wang
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Eastern China ◽  
Summer Precipitation ◽  
Ice Age ◽  
Last Millennium ◽  
Decadal Timescale ◽  
Asian Summer

Abstract. Precipitation/humidity proxies are widely used to reconstruct the historical East Asian summer monsoon (EASM) variation based on the assumption that summer precipitation over eastern China is closely and stably linked to the strength of EASM. However, whether the observed EASM-precipitation relationship (e.g., increased precipitation with a stronger EASM) was stable throughout the past time remains unclear. In this study, we used model outputs from the Paleoclimate Modelling Intercomparison Project Phase Ⅲ and Community Earth System Model to investigate the stability of the EASM-precipitation relationship over the last millennium on different timescales. The model results indicate that the EASM strength (defined as the regionally averaged meridional wind) enhanced in the Medieval Climate Anomaly (MCA; ~ 950–1250 A.D.), during which there was increased precipitation over eastern China, and weakened during the Little Ice Age (LIA; ~ 1500‒1800 A.D.), during which there was decreased precipitation, consistent with precipitation/humidity proxies. However, the simulated EASM-precipitation relationship is only stable on a centennial and longer timescale and is unstable on a multi-decadal timescale. The nonstationary multi-decadal EASM-precipitation relationship broadly exhibits a quasi-60-year period, which may be attributed to the internal variability of the climate system and have no significant correlation to external forcings. Our results have implications for understanding the discrepancy among various EASM proxies on a multi-decadal timescale and highlight the need to rethink reconstructed decadal EASM variations based on precipitation/humidity proxies.

scholarly journals Assessment of time of emergence of anthropogenic deoxygenation and warming: insights from a CESM simulation from 850 to 2100 CE

2019 ◽  
Author(s):  
Angélique Hameau ◽  
Juliette Mignot ◽  
Fortunat Joos
Keyword(s):  
Volcanic Eruptions ◽  
Internal Variability ◽  
Marine Ecosystems ◽  
Natural Variability ◽  
Last Millennium ◽  
Anthropogenic Change ◽  
Methodological Choices ◽  
Deep Waters ◽  
Short Period ◽  
Community Earth System Model

Abstract. Marine deoxygenation and anthropogenic ocean warming are observed and projected to aggravate under continued greenhouse gas emissions. These changes potentially adversely affect the functioning and services of marine ecosystems. A key question is whether marine ecosystems are already or will soon be exposed to environmental conditions not experienced during the last millennium. We find that anthropogenic deoxygenation and warming in the thermocline have today already left the bounds of natural variability in respectively 60 % and 90 % of total ocean area in a forced simulation with the Community Earth System Model (CESM) over the period 850 to 2100. Natural variability is assessed from last millennium (850–1800) results considering forcing from explosive volcanic eruptions, solar irradiance, and greenhouse gases in addition to internal, chaotic variability. Control simulations are typically used to estimate variability. However, natural variability in oxygen (O2) and temperature (T) are systematically larger than internal variability (e.g. the latter amounts to 20 % for T and 60 % for O2 in the thermocline), rendering such estimates of natural variability to be biased low. Results suggest that anthropogenic change in apparent oxygen utilisation (AOU) and in O2 solubility (O2,sol) are earlier detectable by measurements than in O2 in the tropical thermocline, where biological and solubility-driven O2 changes counteract each other. Both natural variability and change in AOU are predominantly driven by variations in circulation with a smaller role for productivity. Ventilation becomes more vigorous in the tropical thermocline by the end of the 21st century, whereas ideal age in deep waters increases by more than 200 years until 2100. Different methodological choices are compared and the time for an anthropogenic signal to emergence (ToE) is earlier in many thermocline regions when using variability from a short period, the control, or estimates from the industrial period instead variability from the last millennium. Our results highlight that published methods lead to deviations in ToE estimates, calling for a careful quantification of variability and that realised anthropogenic change exceeds natural variations in many regions.

scholarly journals Tropical volcanism enhanced the East Asian summer monsoon during the last millennium

2021 ◽  
Author(s):  
Fei Liu ◽  
Chaochao Gao ◽  
Jing Chai ◽  
Alan Robock ◽  
Bin Wang ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
El Niño ◽  
East Asian Summer Monsoon ◽  
Volcanic Eruption ◽  
El Nino ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Volcanic Eruptions ◽  
Last Millennium ◽  
Asian Summer

Abstract Extreme East Asian summer monsoon (EASM) rainfall frequently induces floods that pose threats to millions of people across East Asia. The intensified EASM rainfall has been generally attributed to internal modes of climate variability, while external volcanic forcing has been suggested to suppress the EASM. In contrast to the hydrological weakening theory of volcanic eruptions, we present convergent empirical and modeling evidence for significant intensification of EASM rainfall in response to strong tropical volcanic eruptions. Our paleoclimate proxy analyses show a significantly increased EASM in the first summer after large tropical eruptions from 1470 AD to the present. The multi-proxy ensemble mean demonstrates that the occurrence of an El Niño in the first boreal winter after a volcanic eruption is necessary for the enhanced EASM. The results from the last-millennium climate model simulations show that a volcano-induced El Niño and the associated warm pool air-sea interaction intensify EASM precipitation, overwhelming volcanic-induced moisture deficiency. This work offers a new perspective on the intertwined relationship between external forcing and internal variability in the complex climate system and potential flood disasters resulting from tropical volcanic eruption.

scholarly journals Timescale dependence of the relationship between the East Asian summer monsoon strength and precipitation over eastern China in the last millennium

2018 ◽  
Vol 14 (4) ◽  
pp. 577-591 ◽  
Author(s):  
Jian Shi ◽  
Qing Yan ◽  
Huijun Wang
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Eastern China ◽  
Summer Precipitation ◽  
Ice Age ◽  
Phase Iii ◽  
Last Millennium ◽  
Asian Summer

Abstract. Precipitation/humidity proxies are widely used to reconstruct the historical East Asian summer monsoon (EASM) variations based on the assumption that summer precipitation over eastern China is closely and stably linked to the strength of EASM. However, whether the observed EASM–precipitation relationship (e.g., increased precipitation with a stronger EASM) was stable throughout the past remains unclear. In this study, we used model outputs from the Paleoclimate Modelling Intercomparison Project Phase III and Community Earth System Model to investigate the stability of the EASM–precipitation relationship over the last millennium on different timescales. The model results indicate that the EASM strength (defined as the regionally averaged meridional wind) was enhanced in the Medieval Climate Anomaly (MCA; ∼ 950–1250 AD), during which there was increased precipitation over eastern China, and weakened during the Little Ice Age (LIA; ∼ 1500–1800 AD), during which there was decreased precipitation, consistent with precipitation/humidity proxies. However, the simulated EASM–precipitation relationship is only stable on a centennial and longer timescale and is unstable on a shorter timescale. The nonstationary short-timescale EASM–precipitation relationship broadly exhibits a multi-decadal periodicity, which may be attributed to the internal variability of the climate system and has no significant correlation to external forcings. Our results have implications for understanding the discrepancy among various EASM proxies on a multi-decadal timescale and highlight the need to rethink reconstructed decadal EASM variations based on precipitation/humidity proxies.

Sign in / Sign up

Export Citation Format

Share Document