Central and Northeast India 1000 Year Stalagmite Oxygen Isotope Data Sinha, A.; Berkelhammer, M.B.; Stott, L.D.; Mudelsee, M.; Cheng, H.; Biswas, J. Sinha, A. Berkelhammer, M.B. Stott, L.D. Mudelsee, M. Cheng, H. Biswas, J. Monsoon earth science/paleoclimate/speleothems (delta 18O,calcium carbonate,null,per mil VPDB,null,speleothems,raw,isotope ratio mass spectrometry,N,null) earth science/paleoclimate/speleothems (age,null,null,year Common Era,null,speleothems,null,null,N,null) earth science/paleoclimate/speleothems (Wah Shikar Cave>LATITUDE 25.25>LONGITUDE 91.8667) (Jhumar Cave>LATITUDE 18.8667>LONGITUDE 81.8667) The "internally" generated intraseasonal variability of the Indian Summer Monsoon is characterized by intermittent periods of enhanced ("active") and deficient ("break") precipitation, which produce a quasi east-west precipitation dipole over the Indian subcontinent. Here we present multicentennial-length and near annually-resolved reconstructions of monsoon precipitation, inferred from absolute-dated and instrumentally calibrated speleothem oxygen isotope records from regions (central and northeast India) that have diametric responses to active-break monsoon circulation patterns. On centennial timescales (AD 1400-2008), precipitation variability from these two regions exhibit opposing behavior, oscillating between periods with a persistently "active-dominated" (AD ~1700 to 2007) and a "break- dominated" (AD 1400 to ~1700) regime. The switch between these regimes occurs abruptly (within decades) at a time (AD ~1650-1700) when a proxy record of upwelling intensity from the Arabian Sea suggest an abrupt increase in the monsoon winds. On the basis of these observations, we hypothesize that the frequency distribution of active-break periods varies on centennial timescales, implying a leading role of internal dynamics in governing the ISM response to slowly-evolving changes in the external boundary conditions. STUDY NOTES: Stalagmite oxygen isotope (d18O) data from two caves located in central and northeast India, plus a composite Core Monsoon Zone stalagmite d18O record, composed of Jhumar Cave d18O data combined with previously published Dandak Cave d18O data. The instrumentally calibrated stalagmite oxygen isotope record (JHU-1) from Jhumar Cave in Central India provides a millennial length (AD 1075 to 2007) history of monsoon rainfall variations over the core monsoon zone of India (CMZ). The record contains 642 oxygen isotope measurements with an average temporal resolution of 1.45 years and its chronology is established by counting annual growth layers. A maximum uncertainty of ~10 years at the bottom of the stalagmite is inferred from multiple counts of growth laminae. A suite of 230Th dates were also obtained to test the annual nature of the laminations (Table S2). While all 230Th ages fall on or near the slope that describe the laminae-based age model, we did not use 230Th dates in constructing the age model because of high detrital thorium of JHU-1 stalagmite, which produced substantially large error in 230Th dates (2 sigma > 200 years). The multicentennial-length (AD 1399 to 2007) speleothem d18O record (WS-B) from Wah Shikar Cave in northeast India is established by 625 d18O measurements with an average temporal resolution of 0.97 years (Table S1). The record provides a history of monsoon rainfall variations over northeast India (NEI). The age model for the WS-B stalagmite is developed from seven 230Th dates, which are in correct stratigraphic order, with 2 sigma error ranging from 28 to 70 years (Table S2). Four additional 230Th dates produced unreasonably high error (> 100 years) and were subsequently discarded. The age model is developed by linearly interpolating between individual dates except for the segment between the bottom two dates where we calculated the age at the bottom of the stalagmite by extrapolating the age-depth curve from two prior better-constrained dates. The Jhumar Cave stalagmite d18O data provides a history of monsoon rainfall variations over the core monsoon zone of India (CMZ). The record complements our previously reported millennial-length (AD 625 to 1562), absolute-dated oxygen isotope record (DAN-D) from Dandak Cave (Berkelhammer et al., 2009; Sinha et al, 2007), which is located ~20 km west of Jhumar Cave. Both oxygen isotope time series were linearly interpolated to an annual timescale and averaged (over the period of overlap) to produce a composite oxygen isotope record that provides a continuous history of the CMZ's monsoon rainfall variations over the past ~1400 years (AD 2007-625) (Table S1). The composite record captures nearly every major drought during the instrumental period as well as historic failures of monsoon, including extended intervals of substantially weaker monsoon during the 14th and 17th century. The latter are independently corroborated by historical accounts and other regional proxy records. Site Locations: Jhumar Cave, Central India: 18°52'N, 81°52'E, 600 masl Wah Shikar Cave, Northeast India: 25°15'N, 91°52'E, 1290 masl Dandak Cave: 19°N, 82°E, 400 masl NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Sinha, A. Investigator : Berkelhammer, M.B. Investigator : Stott, L.D. Investigator : Mudelsee, M. Investigator : Cheng, H. Investigator : Biswas, J. 2011-08-07 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/11937 https://www1.ncdc.noaa.gov/pub/data/paleo/speleothem/asia/india/jhumar-wah-shikar2011.txt https://www1.ncdc.noaa.gov/pub/data/paleo/speleothem/asia/india/jhumar-wah-shikar2011.xls https://www1.ncdc.noaa.gov/pub/data/paleo/speleothem/asia/india/jhumar-wah-shikar2011.txt https://www1.ncdc.noaa.gov/pub/data/paleo/speleothem/asia/india/jhumar-wah-shikar2011.xls English https://www.ncdc.noaa.gov/paleo/study/11937 https://www1.ncdc.noaa.gov/pub/data/paleo/speleothem/asia/india/jhumar-wah-shikar2011.txt https://www1.ncdc.noaa.gov/pub/data/paleo/speleothem/asia/india/jhumar-wah-shikar2011.xls Sinha, A., M. Berkelhammer, L. Stott, M. Mudelsee, H. Cheng, and J. Biswas. 2011. The leading mode of Indian Summer Monsoon precipitation variability during the last millennium. Geophysical Research Letters, Vol. 38, L15703, doi:10.1029/2011GL047713 START YEAR: 1075 AD * END YEAR: 2008 AD 81.8667 18.8667 91.8667 25.25