Deglacial trends in Indo-Pacific warm pool hydroclimate in an isotope-enabled Earth system model and implications for isotope-based paleoclimate reconstructions

Abstract The Indo-Pacific Warm Pool (IPWP) is the largest source of atmospheric heating and moisture on Earth, energizing the global moisture and energy budgets and controlling global ocean-atmosphere circulation. However, the mechanisms driving orbital-scale changes in hydroclimate and proxy records of precipitation isotopic composition remain poorly known. Here, we use the isotope-enabled Transient Climate Evolution (iTRACE) experiment to investigate long-term hydroclimate and precipitation isotope changes in the IPWP during the last deglaciation, and their response to different climate forcings (sea level and ice sheet, greenhouse gases, orbital forcing, and meltwater flux). The simulations suggest land-sea configuration as the main factor driving long-term hydroclimate and precipitation isotope changes. The exposure of NW Australian shelf (before 14 ka) excited Bjerknes feedbacks across the equatorial Indian Ocean (IO), leading to a warm/wet western IO and cool/dry eastern IO dipole pattern, with overall drying and more enriched precipitation isotopic compositions over the Maritime Continent. However, the exposed Sunda Shelf and the main body of Sahul Shelf (before 12 ka) experienced locally dry conditions but more depleted precipitation isotopic compositions. Greenhouse gases and orbital forcing contribute to a weaker hydroclimate dipole pattern that opposes the effects of NW Australian shelf exposure. Different regions within the IPWP have different simulated sensitivities to these forcings. The heterogeneous responses of precipitation to different forcings across the Maritime Continent and location-dependent relationships between precipitation and its isotopic composition result from a variety of regional climatological processes and may explain the heterogeneity of isotopic records of hydroclimate around the IPWP.