Chinese stalagmite δ18O controlled by changes in the Indian monsoon during a simulated Heinrich event

Indian monsoon variations during three contrasting climatic periods: The Holocene, Heinrich Stadial 2 and the last interglacial–glacial transition

“…In contrast, moderate iceberg discharges led to a less dry climate during the start of the last glaciation at the MIS 5/4 transition. In agreement with model predictions (Pausata et al, 2011;Gibbson et al, 2014), our study suggeststhat feedback mechanisms are determinant processes to explain the magnitude and distribution of monsoon rainfalls, especially at millennial times scales. Freshwater inputs in the North Atlantic Ocean, the ITCZ location and the Indian Ocean surface temperatures are some feedbacks that change the hydrological cycle in tropical areas and control rainfall distribution and intensity in Central India over geological time scales.…”

“…Southward shifts of the ITCZ are recorded in the Indian Ocean during other Heinrich events (Gibbons et al, 2014) and can explain the strong aridity during the HS 2. Modeling experiments by Pausata et al (2011) Ocean . If the ENSO-controlled Indian Ocean SST variations seem to affect theamount of moisture that the westerlies bring to the Indian monsoon system (Clement et al, 1999;Gibbson et al, 2014), our data suggest, in line with Prasad et al(2014), that Indian summer rainfall distribution is preferentially impacted by the ITCZ position (in link with insolation feedback mechanisms) than by ENSO at centennial, millennial and glacial/interglacial scales.…”

“…Identifying its natural rhythmicity, magnitude, and the physical processes involved is a challenge for present-day and future socio-economic policy predictions. Model studies (Broccoli et al, 2006;Chiang et Bits, 2005;Mohtadi et al, 2014;Pausata et al, 2011;Vernekar et al, 1995) and palaeoclimatic observations (Agnihotri et al, 2002;Fleitmann et al, 2007;Gupta et al, 2003;Hahn et al, 1976;Ponton et al, 2012;Sinha et al, 2007) suggest that abrupt changes of Indian monsoon are in phase with North Atlantic climate variations. These studies further show that changes in the Intertropical Convergence Zone (ITCZ), North Atlantic iceberg discharges, Indian Ocean sea surface temperature (SST) gradient and Himalayan snow cover can explain the rapid atmospheric reorganization between the North Atlantic and the Indian region.…”

Oxygen isotope geochemistry of Laurentide ice-sheet meltwater across Termination I

“…Isotope-enabled GCMs have been used to simulate the geographic distribution of oxygen isotope values in precipitation (Carlson et al, 2008a;LeGrande et al, 2006;Pausata et al, 2011;Risi et al, 2010;Ullman et al, 2014;Werner et al, 2011;Yoshimura et al, 2008). Paleohydrologic records and modeling studies of North America from the LGM show that westerly storm tracks were shifted southward and intensified during the LGM (Oster et al, 2015, and references therein), and d 18 O records also indicate that precipitation was up to 7‰ more negative during glacial intervals .…”

“…In addition, global circulation models (GCMs) that incorporate Rayleigh-type fractionation (Carlson et al, 2008a;LeGrande et al, 2006;Pausata et al, 2011;Risi et al, 2010;Ullman et al, 2014;Werner et al, 2011;Yoshimura et al, 2008) can estimate oxygen isotope heterogeneity in precipitation. These types of models offer an alternative approach to modeling ice-sheet heterogeneity, and recent efforts have begun to link modeled d 18 O w of Pleistocene precipitation with LIS-derived groundwater measurements (Ferguson and Jasechko, 2015).…”