Quaternary Hydroclimate Evolution of the Indian Subcontinent: A Multi-Archive Framework for Interpreting Monsoon Variability and Proxy-System Behaviour

The Indian subcontinent preserves diverse Quaternary palaeoenvironmental archives that record Indian Summer Monsoon (ISM) variability across contrasting climatic and environmental settings. This review synthesizes speleothem, lacustrine, marine, fluvial, aeolian, cryospheric, ecological, and archaeological evidence within a multi-archive framework that explicitly considers proxy sensitivity, archive filtering, chronological uncertainty, and spatial heterogeneity. Multi-archive evidence indicates weakened monsoon circulation during the Last Glacial Maximum, rapid deglacial reorganization including the Younger Dryas, and widespread monsoon intensification during the early Holocene. The subsequent middle-tolate Holocene was characterized by generally declining monsoon strength superimposed by substantial centennial-scale variability. Hydroclimatic instability around 4.2 ka was regionally important but spatially heterogeneous and not uniformly expressed among archives, while the late Holocene and last millennium experienced recurrent drought–wet variability. A central outcome of this synthesis is that apparent disagreement among palaeoclimate records does not necessarily represent contradictory climate histories. Different archives record distinct components of hydroclimate and transform climatic forcing through seasonality, hydrological storage, sediment mixing, ecological response, temporal integration, and other archive-specific processes. Consequently, speleothem, lacustrine, marine, fluvial, and Himalayan records are most informative when interpreted as complementary constraints rather than directly interchangeable climate indicators. Future progress requires processbased and uncertainty-aware integration through proxy-system and isotope-enabled modelling, climate data assimilation, standardized multi-archive networks, and coordinated terrestrial–marine synthesis. This framework portrays the ISM as a spatially heterogeneous and dynamically coupled hydroclimatic system and provides a long-term context for evaluating contemporary hydroclimatic change across South Asia.