Late Quaternary paleoclimate reconstructions in Bhutanese Himalaya based on glacial modelling

Paleoclimate change can be quantified by modelling the paleoglacier extents at well-dated moraines. However, previous studies typically use paleo-precipitation changes derived from climate proxies in other locations to constrain paleo-temperature changes. This approach may lead to significant uncertainties due to the lack of a physical basis and spatial-temporal representativeness. To address this issue, we developed a two-step approach to better constrain the paleo-temperature and precipitation changes. The first step is to identify all potential scenarios for temperature-precipitation changes using a coupled glacial-mass-balance and ice-flow model. In the second step, we incorporate a physics-based parameter k, reflecting the sensitivity of precipitation and temperature change, to determine the most probable temperature-precipitation change. We demonstrate our new approach by reconstructing paleoclimate changes of two valley glaciers in the Bhutanese Himalaya (BH). This approach derives a set of temperature reductions of −4.14 °C, −4.08 °C, −0.93 °C, −0.33 ∼ −0.57 °C, and − 0.31 ∼ −0.52 °C, with their corresponding precipitation decreases of 21.4%, 21.0%, 5.2%, 1.7–3.3%, and 1.6–3.0% relative to the present, during the Last Glacial Maximum, Heinrich event 1, Younger Dryas, Neoglacial, and Little Ice Age in BH, respectively. The reconstructed cold and dry climates in BH are consistent with the paleoclimate reconstructions across the Tibetan Plateau, but our approach improved the accuracy of regional paleoclimate reconstructions. These results suggest that temperature change dominates the glacial fluctuations in BH, with additional influences from solar insolation, oceanic and atmospheric circulation changes, and volcanic eruptions.