South Asian Summer Monsoon precipitation variability during late Pliocene: Role of Indonesian Throughflow

South Asian Monsoon Variability and Arctic Sea Ice Extent Linkages During the Late Pliocene

“…Observations suggest that the SoAM intensified during intervals III (MPWP; 3.22-3.06 Ma) and I (2.93-2.68 Ma) and weakened during intervals IV (3.39-3.22 Ma) and II (3.06-2.93 Ma). These results are consistent with previous eastern Arabian Sea (Sarathchandraprasad et al, 2021;Tripathi et al, 2017) and South China Sea (Zhang et al, 2009) studies, which suggest an intensification of SoAM during the MPWP. Cai et al, 2019 also observes from the eastern Arabian Sea (IODP 355, Site U1456) using silicate weathering that the SoAM was weak from 3.8 to 3.3 Ma and from 2.7 to 1.2 Ma.…”

“…Thus, reduced surface productivity and denitrification during these two intervals (intervals IV and II) suggest weakened SoAM compared to other two intervals. Weakened SoAM during these intervals is also supported by reduced chemical weathering as shown by low K/Al ratio during these periods (Figure 2d; Sarathchandraprasad et al, 2021). In contrast, during Interval III and I, relatively high δ 15 N values indicate enhanced denitrification (Figure 2a).…”

“…This is likely because the model is not able to capture boundary conditions, as noted in the recent The Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) ensemble (Han et al., 2021). For example, tectonically induced changes in Indonesian Throughflow and/or South African plateaus may have resulted in SoAM intensification at 2.95 Ma (e.g., Sarathchandraprasad et al., 2021; Zhang & Liu, 2010).…”

“…The SoAM variability, in the present study, is reconstructed using multiple proxies of denitrification (δ 15 N) and surface water productivity (TOC and TN) from the eastern Arabian Sea supported by a chemical weathering proxy (K/Al; Sarathchandraprasad et al., 2021) and model‐data hybrid analysis. Denitrification is the process in which nitrate is used as an oxidizing agent for respiration of the organic matter when the oxygen level falls below 1 μM (Altabet et al., 1995; Bange et al., 2001).…”

“…Increased Arctic SIE should have weakened the SoAM; however, SoAM strengthened despite adverse thermodynamical and dynamical effects. This strengthening has been attributed to the tectonically induced reorganization of Indonesian Throughflow (Sarathchandraprasad et al, 2021). The northward movement of the Australian Plate during mid-Piacenzian may have changed the source of Indonesian Throughflow water from the South to North Pacific Ocean, which may have caused 4°C cooling of the southern tropical Indian Ocean subsurface and surface waters at 2.95 Ma (Cane & Molnar, 2001;Karas et al, 2009Karas et al, , 2011.…”