Proxy-Model Constraints on Holocene Indian Summer Monsoon Variability and Seasonality in Northwest India

The Indian Summer Monsoon (ISM) is a critical driver of global water availability, agriculture, and food security, yet future climate projections rely largely on instrumental records that are insufficient to capture its long-term, non-linear variability. The Holocene epoch (~11.7 ka to present) provides a crucial framework for resolving these dynamics and evaluating climate models under near-modern boundary conditions, as well as constraining nonlinear monsoon behaviour and large-scale teleconnections through the investigation of abrupt events. The margins of the Thar Desert represent a highly sensitive archive of ISM variability, where monsoon weakening and abrupt climatic events have been linked to the decline of the Bronze Age Indus Civilisation. Despite this significance, continuous high-resolution Holocene records and a clear understanding of seasonal precipitation dynamics remain absent from this region.

Here, we reconstruct Holocene ISM variability and its impacts along the margins of the Thar Desert using an integrated proxy-model approach. Multi-proxy lake sediment records are compared with Paleoclimate Modelling Intercomparison Project (PMIP) and transient TraCE-21ka climate simulations. Results indicate an early Holocene shift from arid to wetter conditions. PMIP results indicate significant mid-Holocene seasonality changes. Furthermore, lake water mass balance modelling is employed to quantify seasonal precipitation–evaporation dynamics during abrupt climatic events captured in proxy records. By resolving the mechanisms driving Holocene monsoon variability and non-linear responses, this work offers insights for refining regional climate projections and assessing future climate risks.