South Asian summer monsoon variability during the last ∼54 kyrs inferred from surface water salinity and river runoff proxies

BAYSPLINE: A New Calibration for the Alkenone Paleothermometer

“…BAYSPLINE's treatment of the slope attenuation is critical for the interpretation of U K ′ 37 data from tropical locations, where traditional linear calibrations will underestimate the magnitude of SST change. To illustrate this, we investigate the magnitude of cooling during the LGM in the Indo-Pacific Warm Pool (IPWP), using multiple SST proxies from 77 sites (data from Bard et al, 1997;Budziak, 2001;Dahl & Oppo, 2006;de Garidel-Thoron et al, 2007;Gebregiorgis et al, 2016;Gibbons et al, 2014;Huguet et al, 2006;Kudrass et al, 2001;Mohtadi et al, 2010Mohtadi et al, , 2014Palmer & Pearson, 2003;Pelejero et al, 1999;Rippert et al, 2015;Romahn et al, 2014;Saraswat et al, 2013;Schulte & Müller, 2001;Shintani et al, 2008Shintani et al, , 2011Sonzogni et al, 1998;Stott et al, 2007;Tierney et al, 2016;Waelbroeck et al, 2009;Xu et al, 2008Xu et al, , 2010Yamamoto et al, 2013). See the supporting information for details concerning the data compilation, which uses methodology from Bemis et al (1998), Bronk Ramsey (1995, 2008, Tierney et al (2016), Holloway et al (2016, Khider et al (2015), Regenberg et al (2014), Reimer et al (2013), Tierney and Tingley (2015).…”

Enhanced Himalayan Glacial Melting During YD and H1 Recorded in the Northern Bay of Bengal

“…These two events occurred within well‐known episodes of weak northern hemisphere monsoon systems, as indicated by strong δ 18 O enrichment in Indian and Chinese stalagmite records (Cai et al, ; Dutt et al, ; Kathayat et al, ; Sinha et al, ; Wang et al, ). The weakening of the ISM during the YD and H1 is also manifested by relatively heavy δ 18 O (enriched in 18 O) values in numerous BoB core sediments (Figures and S1; Gebregiorgis et al, ; Govil & Naidu, ; Kudrass et al, ; Marzin et al, ; Rashid et al, ; Sijinkumar et al, ]. We compare our δ 18 O G. ruber record with that of SO93‐126KL, which is located 42 km southeast of our site (Figures and b; Kudrass et al, ].…”

“…If the δ 18 O decrease were solely caused by SST changes, it would require a centennial scale mixed layer warming by 2 and 3.5°C during YD and H1, respectively. The resolution of available temperature reconstructions of the BoB mixed layer is insufficient to unravel centennial‐scale changes in SST (Figure S2; Gebregiorgis et al, ; Govil & Naidu, ; Kudrass et al, ; Saraswat et al, ). The δ 18 O record of SO93‐126KL does not support a warming of 3.5 and 2°C during YD and H1, respectively.…”

“…Extrapolating catchment-scale Himalayan glacier reconstructions to a regional scale is, however, compounded by valley hypsometry-and longitude-dependent disparate responses of Himalayan glaciers (Amidon et al, 2013, Finkel et al, 2003, Pratt-Sitaula et al, 2011. Glacial-interglacial-and stadialinterstadial-scale reconstructions of changes in Ganges-Brahmaputra river (GBR) and Irrawaddy runoff extracted from BoB sediment sequences provide spatially integrated insights into ISM variability (Gebregiorgis et al, 2016;Govil & Naidu, 2011;Kudrass et al, 2001;Marzin et al, 2013;Rashid et al, 2011;Saraswat et al, 2013;Sijinkumar et al, 2016). However, relative to the GBR mouth, the core location of available records is likely not close enough to fully capture meltwater signatures and disentangle them from monsoonal imprints.…”

Evolution of the Indian summer monsoon during the interval 32.7–11.4cal. ka BP: Evidence from the Baoxiu peat, Yunnan, southwest China

“…TOC records (Schulz et al, 1998) and total reflectance (L ⁄ ) data (Deplazes et al, 2013) from the Arabian Sea provide additional evidence for a weak ISM during 23-19 ka BP. Seawater d 18 O and Ba/Ca records from sediment core SK 168/GC-1 in the Andaman Sea suggest that the climate during 23-19 ka BP was characterized by a extremely weak ISM circulation and strongly reduced runoff (Gebregiorgis et al, 2016) A positive excursion from the same interval in stalagmite d 18 O records from Sanxing also suggests a weakened ISM (Jiang et al, 2014). K/Rb ratios from Baoxiu peat in this study are also significantly lower between 23 and 19 ka BP, indicating very dry climatic conditions resulting from a weak ISM.…”