Chemical weathering and the ensuing atmospheric carbon dioxide consumption has long been considered to work on geological time periods until recently when some modelling and natural records have shown that the weathering-related CO2 consumption can change at century to glacial-interglacial time scale. Last glacial to interglacial transition period is a best test case to understand the interplay between Pco2-temperature-chemical weathering when a pulse of rapid chemical weathering was initiated. Here we show, from a high resolution 54 ka record from the Andaman Sea in the northern Indian Ocean, that the chemical weathering responds to deglacial to mid-Holocene summer monsoon intensification in the Myanmar watersheds. The multi-proxy data (Al/K, CIA, Rb/Sr, 87Sr/86Sr for degree of weathering and 143Nd/144Nd for provenance) reveal an increase in silicate weathering with initiation of interglacial warm climate at ~17.7 ka followed by a major change at 15.5 ka. Inferred changes in chemical weathering have varied in tandem with the regional monsoonal proxies (δ18Osw-salinity changes of Northern Indian Ocean, effective Asian moisture content and δ18O records of Chinese caves) and are synchronous with changes in summer insolation at 30°N and δ18O of GISP2 implying that chemical weathering was not a later amplifier but worked in tandem with global climate change.

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We present a record of glacial to Holocene 230Thxs normalized sediment mass fluxes for a site located on the eastern flank of the Carlsberg Ridge, Arabian Sea to evaluate carbonate burial, preservation and surface ocean changes spanning the last 38 ka. Sediment fluxes (0.81–3.70 g cm−2 ka−1) indicate dominant carbonate rain (0.44–1.83 g cm−2 ka−1), followed by 232Th‐based lithogenic flux (0.36–1.42 g cm−2 ka−1), with higher fluxes during the Holocene and the late Marine Isotope Stage (MIS) 3 and extremely low fluxes during MIS 2. Despite large variations in sediment mass fluxes, the average flux of 230Thxs scavenged over the last 38 ka remained nearly constant. In contrast, the large variations in the initial 230Thxs activity display the effect of variable dilution by the carbonate flux. Analysis of 232Th‐based lithogenic flux documents a dominant fluvial source and links its variability to changing SW monsoon precipitation in the Indus source region. Comparison of the last 38 ka carbonate flux record with the present‐day carbonate flux intercepted at the closest mooring at 3915 m depth demonstrates burial efficiency of 80 to 99% to the seabed during the Holocene and late MIS 3 and 53% for the MIS 2. Calculated carbonate preservation efficiency relative to the trapped upper ocean carbonate flux provides evidence for a productivity control of the preserved carbonate flux, which indicates high preservation during the Holocene (63±10%), and MIS 3 (77±24%) and low during MIS 2 (41±15%). Our results suggest that the eastern flank of Carlsberg Ridge experienced enhanced carbonate production during the Holocene and MIS 3 compared to MIS 2. We suggest that changing oceanographic conditions in near‐surface waters have changed the carbonate supply to the sea floor accounting for the glacial to Holocene pattern with increased supply due to the intensified SW monsoon and reduced input associated with the weakened SW monsoon.

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