scholarly journals Decreasing Indian summer monsoon on the northern Indian sub-continent during the last 180 years: evidence from five tree-ring cellulose oxygen isotope chronologies

2018 ◽  
Vol 14 (5) ◽  
pp. 653-664 ◽  
Author(s):  
Chenxi Xu ◽  
Masaki Sano ◽  
Ashok Priyadarshan Dimri ◽  
Rengaswamy Ramesh ◽  
Takeshi Nakatsuka ◽  
...  
Keyword(s):  
High Resolution ◽  
Oxygen Isotope ◽  
Tree Ring ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Southern Oscillation ◽  
Oxygen Isotope Fractionation ◽  
Northern India ◽  
Tree Ring Cellulose

Abstract. We have constructed a regional tree-ring cellulose oxygen isotope (δ18O) record for the northern Indian sub-continent based on two new records from northern India and central Nepal and three published records from northwestern India, western Nepal and Bhutan. The record spans the common interval from 1743 to 2008 CE. Correlation analysis reveals that the record is significantly and negatively correlated with the three regional climatic indices: all India rainfall (AIR; r  =  −0.5, p  <  0.001, n  =  138), Indian monsoon index (IMI; r  =  −0.45, p  <  0.001, n  =  51) and the intensity of monsoonal circulation (r  =  −0.42, p  <  0.001, n  =  51). The close relationship between tree-ring cellulose δ18O and the Indian summer monsoon (ISM) can be explained by oxygen isotope fractionation mechanisms. Our results indicate that the regional tree-ring cellulose δ18O record is suitable for reconstructing high-resolution changes in the ISM. The record exhibits significant interannual and long-term variations. Interannual changes are closely related to the El Niño–Southern Oscillation (ENSO), which indicates that the ISM was affected by ENSO in the past. However, the ISM–ENSO relationship was not consistent over time, and it may be partly modulated by Indian Ocean sea surface temperature (SST). Long-term changes in the regional tree-ring δ18O record indicate a possible trend of weakened ISM intensity since 1820. Decreasing ISM activity is also observed in various high-resolution ISM records from southwest China and Southeast Asia, and may be the result of reduced land–ocean thermal contrasts since 1820 CE.

scholarly journals Tree-ring-inferred glacier mass balance variation in southeastern Tibetan Plateau and its linkage with climate variability

2013 ◽  
Vol 9 (6) ◽  
pp. 2451-2458 ◽  
Author(s):  
J. Duan ◽  
L. Wang ◽  
L. Li ◽  
Y. Sun
Keyword(s):  
Tibetan Plateau ◽  
Climate Variability ◽  
Mass Balance ◽  
Tree Ring ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Dominant Factor ◽  
Glacier Mass Balance ◽  
Monsoon Precipitation

Abstract. A large number of glaciers in the Tibetan Plateau (TP) have experienced wastage in recent decades. And the wastage is different from region to region, even from glacier to glacier. A better understanding of long-term glacier variations and their linkage with climate variability requires extending the presently observed records. Here we present the first tree-ring-based glacier mass balance (MB) reconstruction in the TP, performed at the Hailuogou Glacier in southeastern TP during 1868–2007. The reconstructed MB is characterized mainly by ablation over the past 140 yr, and typical melting periods occurred in 1910s–1920s, 1930s–1960s, 1970s–1980s, and the last 20 yr. After the 1900s, only a few short periods (i.e., 1920s–1930s, the 1960s and the late 1980s) were characterized by accumulation. These variations can be validated by the terminus retreat velocity of Hailuogou Glacier and the ice-core accumulation rate in Guliya and respond well to regional and Northern Hemisphere temperature anomaly. In addition, the reconstructed MB is significantly and negatively correlated with August–September all-India monsoon rainfall (AIR) (r1871-2008 = −0.342, p < 0.0001). These results suggest that temperature variability is the dominant factor for the long-term MB variation at the Hailuogou Glacier. Indian summer monsoon precipitation does not affect the MB variation, yet the significant negative correlation between the MB and the AIR implies the positive effect of summer heating of the TP on Indian summer monsoon precipitation.

scholarly journals Decreasing Indian summer monsoon in northern Indian sub-continent during the last 180 years: evidence from five tree cellulose oxygen isotope chronologies

2017 ◽  
Author(s):  
Chenxi Xu ◽  
Masaki Sano ◽  
Ashok Dimri ◽  
Rengaswamy Ramesh ◽  
Takeshi Nakatsuka ◽  
...  
Keyword(s):  
Correlation Analysis ◽  
Oxygen Isotope ◽  
Tree Ring ◽  
Indian Summer Monsoon ◽  
New Records ◽  
North India ◽  
Climatic Indices ◽  
Central Nepal ◽  
Northwest India ◽  
Tree Ring Cellulose

Abstract. We have constructed a regional tree ring cellulose oxygen isotope (δ18O) record for the northern Indian sub-continent based on two new records from north India and central Nepal and three published records from Northwest India, western Nepal and Bhutan. The record spans the interval from 1743–2008 CE. Correlation analysis reveals that the record is significantly negatively correlated with the three regional climatic indices: All India Rainfall (r = −0.5, p 

scholarly journals Evaluating the timing and structure of the 4.2 ka event in the Indian summer monsoon domain from an annually resolved speleothem record from Northeast India

2018 ◽  
Vol 14 (12) ◽  
pp. 1869-1879 ◽  
Author(s):  
Gayatri Kathayat ◽  
Hai Cheng ◽  
Ashish Sinha ◽  
Max Berkelhammer ◽  
Haiwei Zhang ◽  
...  
Keyword(s):  
Climate Change ◽  
High Resolution ◽  
Oxygen Isotope ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Northeast India ◽  
Large Array ◽  
Long Period ◽  
Proxy Records ◽  
Proxy Reconstructions

Abstract. A large array of proxy records suggests that the “4.2 ka event” marks an approximately 300-year long period (∼3.9 to 4.2 ka) of major climate change across the globe. However, the climatic manifestation of this event, including its onset, duration, and termination, remains less clear in the Indian summer monsoon (ISM) domain. Here, we present new oxygen isotope (δ18O) data from a pair of speleothems (ML.1 and ML.2) from Mawmluh Cave, Meghalaya, India, that provide a high-resolution record of ISM variability during a period (∼3.78 and 4.44 ka) that fully encompasses the 4.2 ka event. The sub-annually to annually resolved ML.1 δ18O record is constrained by 18 230Th dates with an average dating error of ±13 years (2σ) and a resolution of ∼40 years, which allows us to characterize the ISM variability with unprecedented detail. The inferred pattern of ISM variability during the period contemporaneous with the 4.2 ka event shares broad similarities and key differences with the previous reconstructions of ISM from the Mawmluh Cave and other proxy records from the region. Our data suggest that the ISM intensity, in the context of the length of our record, abruptly decreased at ∼4.0 ka (∼±13 years), marking the onset of a multi-centennial period of relatively reduced ISM, which was punctuated by at least two multi-decadal droughts between ∼3.9 and 4.0 ka. The latter stands out in contrast with some previous proxy reconstructions of the ISM, in which the 4.2 ka event has been depicted as a singular multi-centennial drought.

scholarly journals Tree-ring inferred glacier mass balance variation in southeastern Tibetan Plateau and its linkage with climate variability

2013 ◽  
Vol 9 (4) ◽  
pp. 3663-3680
Author(s):  
J. Duan ◽  
L. Wang ◽  
L. Li ◽  
Y. Sun
Keyword(s):  
Tibetan Plateau ◽  
Climate Variability ◽  
Mass Balance ◽  
Tree Ring ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Dominant Factor ◽  
Glacier Mass Balance ◽  
Monsoon Precipitation

Abstract. A large number of glaciers in the Tibetan Plateau (TP) have experienced wastage in recent decades. And the wastage is different from region to region, even from glacier to glacier. A better understanding of long-term glacier variations and their linkage with climate variability requires extending the presently observed records. Here we present the first tree-ring-based glacier mass balance (MB) reconstruction in the TP, performed at the Hailuogou Glacier in southeastern TP during 1865–2007. The reconstructed MB is characterized mainly by ablation over the past 143 yr, and typical melting periods occurs in 1910s–1920s, 1930s–1960s, 1970s–1980s, and the last 20 yr. After the 1900s, only a few short periods (i.e., 1920s–1930s, the 1960s and the late 1980s) is characterized by accumulation. These variations can be validated by the terminus retreat velocity of the Hailuogou Glacier and the ice-core accumulation rate in Guliya and respond well to regional and Northern Hemisphere temperature anomaly. In addition, the reconstructed MB is significantly and negatively correlated with August-September all-Indian monsoon precipitation (AIR) (r1871–2008= −0.342, p < 0.0001). These results suggest that temperature variability is the dominant factor for the long-term MB variation at the Hailuogou Glacier. Indian summer monsoon precipitation doesn't affect the MB variation, yet the significant negative correlation between the MB and the AIR implies the positive effect of summer heating of the TP on Indian summer monsoon precipitation.

scholarly journals Climate Precursors of Satellite Water Marker Index for Spring Cholera Outbreak in Northern Bay of Bengal Coastal Regions

2021 ◽  
Vol 18 (19) ◽  
pp. 10201
Author(s):  
Tomomichi Ogata ◽  
Marie-Fanny Racault ◽  
Masami Nonaka ◽  
Swadhin Behera
Keyword(s):  
Climate Variability ◽  
Summer Monsoon ◽  
Disease Transmission ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
Summer Monsoon Rainfall ◽  
South Asian Summer Monsoon ◽  
Public Health Response ◽  
Bengal Delta ◽  
Northern India

Cholera is a water-borne infectious disease that affects 1.3 to 4 million people, with 21,000 to 143,000 reported fatalities each year worldwide. Outbreaks are devastating to affected communities and their prospects for development. The key to support preparedness and public health response is the ability to forecast cholera outbreaks with sufficient lead time. How Vibrio cholerae survives in the environment outside a human host is an important route of disease transmission (see a review of Racault et al. 2019). Thus, identifying the environmental and climate drivers of these pathogens is highly desirable. Here, we elucidate for the first time a mechanistic link between climate variability and cholera (Satellite Water Marker; SWM) index in the Bengal Delta, which allows us to predict cholera outbreaks up to two seasons earlier. High values of the SWM index in fall were associated with above-normal summer monsoon rainfalls over northern India. In turn, these correlated with the La Niña climate pattern that was traced back to the summer monsoon and previous spring seasons. We present a new multi-linear regression model that can explain 50% of the SWM variability over the Bengal Delta based on the relationship with climatic indices of the El Niño Southern Oscillation, Indian Ocean Dipole, and summer monsoon rainfall during the decades 1997–2016. Interestingly, we further found that these relationships were non-stationary over the multi-decadal period 1948–2018. These results bear novel implications for developing outbreak-risk forecasts, demonstrating a crucial need to account for multi-decadal variations in climate interactions and underscoring to better understand how the south Asian summer monsoon responds to climate variability.

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