Stable isotope record of middle Eocene summer monsoon and its instability in eastern China

Ma, Yiquan; Fan, Majie; Lu, Yongchao; Liu, Huimin; Zhang, Shoupeng; Liu, Xiaofeng

doi:10.1016/j.gloplacha.2019.02.007

Cited by 22 publications

(7 citation statements)

References 51 publications

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“…IPSL-CM5A2 (Sepulchre et al, 2019) is composed of the atmospheric LMDZ5 model (Hourdin et al, 2013), the land surface ORCHIDEE model (Krinner et al, 2005) and the NEMO model including oceanic, biogeochemical and seaice components (Madec, 2016). The atmospheric grid has a resolution of 3.75 • (longitude) by 1.89 • (latitude) and 39 vertical layers from the surface up to 40 km high, and the tripolar oceanic grid has a resolution varying between 0.5 • and 2 • and 30 vertical layers.…”

Section: Model Description and Validationmentioning

confidence: 99%

The origin of Asian monsoons: a modelling perspective

et al. 2020

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Abstract. The Cenozoic inception and development of the Asian monsoons remain unclear and have generated much debate, as several hypotheses regarding circulation patterns at work in Asia during the Eocene have been proposed in the few last decades. These include (a) the existence of modern-like monsoons since the early Eocene; (b) that of a weak South Asian monsoon (SAM) and little to no East Asian monsoon (EAM); or (c) a prevalence of the Intertropical Convergence Zone (ITCZ) migrations, also referred to as Indonesian–Australian monsoon (I-AM). As SAM and EAM are supposed to have been triggered or enhanced primarily by Asian palaeogeographic changes, their possible inception in the very dynamic Eocene palaeogeographic context remains an open question, both in the modelling and field-based communities. We investigate here Eocene Asian climate conditions using the IPSL-CM5A2 (Sepulchre et al., 2019) earth system model and revised palaeogeographies. Our Eocene climate simulation yields atmospheric circulation patterns in Asia substantially different from modern conditions. A large high-pressure area is simulated over the Tethys ocean, which generates intense low tropospheric winds blowing southward along the western flank of the proto-Himalayan–Tibetan plateau (HTP) system. This low-level wind system blocks, to latitudes lower than 10∘ N, the migration of humid and warm air masses coming from the Indian Ocean. This strongly contrasts with the modern SAM, during which equatorial air masses reach a latitude of 20–25∘ N over India and southeastern China. Another specific feature of our Eocene simulation is the widespread subsidence taking place over northern India in the midtroposphere (around 5000 m), preventing deep convective updraught that would transport water vapour up to the condensation level. Both processes lead to the onset of a broad arid region located over northern India and over the HTP. More humid regions of high seasonality in precipitation encircle this arid area, due to the prevalence of the Intertropical Convergence Zone (ITCZ) migrations (or Indonesian–Australian monsoon, I-AM) rather than monsoons. Although the existence of this central arid region may partly result from the specifics of our simulation (model dependence and palaeogeographic uncertainties) and has yet to be confirmed by proxy records, most of the observational evidence for Eocene monsoons are located in the highly seasonal transition zone between the arid area and the more humid surroundings. We thus suggest that a zonal arid climate prevailed over Asia before the initiation of monsoons that most likely occurred following Eocene palaeogeographic changes. Our results also show that precipitation seasonality should be used with caution to infer the presence of a monsoonal circulation and that the collection of new data in this arid area is of paramount importance to allow the debate to move forward.

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Section: Model Description and Validationmentioning

confidence: 99%

The origin of Asian monsoons: a modelling perspective

et al. 2020

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“…The results show that the East Asian summer monsoon is significantly sensitive to the moist soil in the Yangtze River Delta ( Zuo and Zhang et al, 2016). Moreover, in the 21st century, there is an East Asian summer monsoon in eastern China, and the climate is unstable (Ma et al, 2019). But basically, the distribution of drought and flood in the south of China is opposite to that in other regions.…”

Section: Introductionmentioning

confidence: 99%

Distribution Pattern of Soil Organic Carbon and Its Regional Humification Constant in the Coastal Monsoon Region of Eastern China

Liu

Xie

Wang

et al. 2021

Preprint

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Soils are an important pool for storing organic carbon. Soil organic carbon (SOC) content is generally considered as an important indicator to evaluate farmland soil quality. The loss of SOC causes soil degradation and reduces the sustainability of farmland. In order to reveal the distribution pattern of SOC in the coastal monsoon area of eastern China, and to clarify the macro dominant factors of SOC accumulation caused by temperature and precipitation, this paper analyzed the distribution pattern of SOC in the coastal monsoon area of eastern China by using the SOC data collected from the national soil testing and formula fertilization data set, and discussed the effects of temperature and precipitation on SOC content. According to the provincial administrative divisions, the distribution of SOC in the coastal monsoon areas of eastern China from Heilongjiang Province to Hainan Province was calculated. According to the annual average temperature < 10.18℃, 10.18 ℃ ~ 20.95℃, > 20.95℃, annual average precipitation 0 ~ 400 mm, 400 ~ 800 mm, > 800 mm, the study area was divided into different regions, and the effects of annual average temperature and annual average precipitation on SOC content were studied. In the region with annual average temperature less than 10.18℃, the temperature had a negative correlation with the accumulation of organic carbon, and the ratio of precipitation and temperature had a positive correlation with the accumulation of SOC; In the region of 10.18℃~20.95℃, the annual average temperature and annual average precipitation had a significant positive correlation, and the ratio of precipitation and temperature had a positive correlation with the accumulation of SOC; In the region > 20.95℃, the temperature had a negative correlation with the accumulation of organic carbon, and the ratio of precipitation and temperature was not related to the accumulation of SOC. In the range of 0 ~ 400 mm of annual average precipitation, the temperature had a positive correlation with the accumulation of SOC, and the ratio of precipitation and temperature had a negative correlation with the accumulation of SOC; In the range of 400 ~ 800 mm of annual average precipitation, the temperature had a negative correlation with the accumulation of SOC, and the ratio of precipitation and temperature had a positive correlation with the accumulation of SOC; In the region > 800 mm of annual average precipitation, the temperature had a positive correlation with the accumulation of organic carbon before the annual average temperature of 20.95℃, and after the annual average temperature of 20.95℃, the temperature had a negative correlation with the accumulation of organic carbon, and the ratio of precipitation and temperature had no significant effect on the accumulation of SOC. On the macro scale, the annual average temperature and precipitation had significant effects on the distribution pattern of SOC in the coastal monsoon area of eastern China. According to the influence of annual average temperature and annual average precipitation on SOC accumulation, a comprehensive model based on the annual average temperature and annual average precipitation on SOC accumulation is established. Through regression verification of the model, the correlation coefficient, r = 0.9998**, the cubic curve equation could better simulated the relationship between the predicted value and the real value of SOC, r = 0.7048**,the model can reflect the cumulative effect of annual average temperature and annual average precipitation on SOC accumulation Combined with the impact.

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“…Similar to Lunt et al (2012), Lunt et al (2021) only focused on temperature and CO 2 -based metrics. The majority of recent studies looking at Eocene hydroclimate have focused on reconstructing evidence for the Asian monsoon (e.g., Farnsworth et al, 2019;Licht et al, 2014;Ma et al, 2019;Quan et al, 2012;Xie et al, 2019). There are very few studies, and in particular modeling studies, focusing on Africa.…”

Section: Introductionmentioning

confidence: 99%

African Hydroclimate During the Early Eocene From the DeepMIP Simulations

Williams

Lunt

Salzmann

et al. 2022

Paleoceanog and Paleoclimatol

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The early Eocene (∼56–48 Myr ago) is characterized by high CO2 estimates (1,200–2,500 ppmv) and elevated global temperatures (∼10°C–16°C higher than modern). However, the response of the hydrological cycle during the early Eocene is poorly constrained, especially in regions with sparse data coverage (e.g., Africa). Here, we present a study of African hydroclimate during the early Eocene, as simulated by an ensemble of state‐of‐the‐art climate models in the Deep‐time Model Intercomparison Project (DeepMIP). A comparison between the DeepMIP pre‐industrial simulations and modern observations suggests that model biases are model‐ and geographically dependent, however, these biases are reduced in the model ensemble mean. A comparison between the Eocene simulations and the pre‐industrial suggests that there is no obvious wetting or drying trend as the CO2 increases. The results suggest that changes to the land sea mask (relative to modern) in the models may be responsible for the simulated increases in precipitation to the north of Eocene Africa. There is an increase in precipitation over equatorial and West Africa and associated drying over northern Africa as CO2 rises. There are also important dynamical changes, with evidence that anticyclonic low‐level circulation is replaced by increased south‐westerly flow at high CO2 levels. Lastly, a model‐data comparison using newly compiled quantitative climate estimates from paleobotanical proxy data suggests a marginally better fit with the reconstructions at lower levels of CO2.

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Stable isotope record of middle Eocene summer monsoon and its instability in eastern China

Cited by 22 publications

References 51 publications

The origin of Asian monsoons: a modelling perspective

The origin of Asian monsoons: a modelling perspective

Distribution Pattern of Soil Organic Carbon and Its Regional Humification Constant in the Coastal Monsoon Region of Eastern China

African Hydroclimate During the Early Eocene From the DeepMIP Simulations

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