Modeling the Late Pliocene with AWI-CM3 as a contribution to PlioMIP3 core experiments

The Late Pliocene, particularly the Marine Isotope Stage KM5c (3.205 Ma BP) has been increasingly proposed as an analog to future climate change, especially considering changes in the hydrological cycle, monsoon systems, and atmospheric and ocean warming above Pre-Industrial (1850 CE) and historical levels. The Pliocene Modeling Intercomparison Project (PlioMIP), now in its third phase (PlioMIP3), seeks to explore climate of the Pliocene based on a combination of climate model simulations and proxy data reconstructions. One of its goals is also to assess the analogy between past and future climates and to quantify climate sensitivity to Pliocene boundary conditions. This work shall help to improve climate models and their application for both past and future warm climates and to provide a paleoclimate-informed assessment of uncertainties in modeled warm climates. With this manuscript we present the PlioMIP3 core simulations for the pre-industrial control (PI) and the Late Pliocene (LP) based on the AWI Climate Model, Version 3 (AWI-CM3). This represents the first application of AWI-CM3 at tectonic timescales which necessitates more extensive adjustment of model setups than the application for recent climate. We therefore take advantage of the opportunity to also document more generally the methods we devised to generate AWI-CM3 model setups for paleoclimate research under geographies that differ from the modern reference state. AWI-CM3 simulates a Late Pliocene climate that is about 4 °C warmer than the pre-industrial reference, with land warming exceeding ocean warming by a factor of 1.2. Polar amplification is particularly pronounced, with Antarctic surface air temperature anomalies exceeding 6 °C while Arctic anomalies reach 4 °C to 5 °C. In comparison to the previous PlioMIP2, this places AWI-CM3 among the warmer ensemble members, consistent with a relatively high equilibrium climate sensitivity of ∼ 4 °C. Our simulations also display an intensified hydrological cycle, with global mean precipitation increasing by 0.31 mm d −1 . The ocean surface warms globally to about 3.06 °C, accompanied by contrasting salinity trends, with salinization of the North Atlantic (+3 PSU) and freshening of the Arctic (–2.5 PSU) and Indian (–1 PSU) Oceans. Additionally, the meridional overturning circulation (MOC) reorganizes, with the Atlantic MOC strengthening by about 8 Sv, the Pacific MOC remaining inactive, and the global Antarctic Bottom Water cell being substantially reduced (11 Sv weaker relative to PI). We find reduced global sea-ice extent, that is halved with respect to PI in the Southern Hemisphere, and enhanced northward ocean heat transport in the North Atlantic. Overall, AWI-CM3 reproduces the large-scale climate features of the Late Pliocene inferred from proxy records and the PlioMIP2 ensemble, while highlighting key ocean–atmosphere feedbacks shaping this warm climate. • We describe the methodology to derive the PlioMIP3 core experiments with AWI-CM3. • We explore AWI-CM3 sensitivity to Pliocene boundary conditions based on literature. • We also present the large-scale patterns of our simulated Late Pliocene climate.