Evaluating the large-scale hydrological cycle response within the PlioMIP2 ensemble

Abstract

Abstract. The mid-Pliocene (~ 3 million years ago) is one of the most recent warm periods with high CO2 concentrations in the atmosphere and resulting high temperatures and is often cited as an analog for near-term future climate change. Here, we apply a moisture budget analysis to investigate the response of the large-scale hydrological cycle at low latitudes within a 13-model ensemble from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). The results show that increased atmospheric moisture content within the mid-Pliocene ensemble (the thermodynamic effect) results in wetter conditions over the deep tropics, i.e., the Pacific intertropical convergence zone (ITCZ) and the Maritime Continent, and drier conditions over the subtropics. The thermodynamic effect is to some extent offset by a dynamic effect involving a northward shift of the Hadley circulation that dries the deep tropics and moistens the subtropics in the Northern Hemisphere (i.e., the subtropical Pacific). From the perspective of Earth’s energy budget, the enhanced southward cross-equatorial atmospheric transport (0.22 PW), induced by the hemispheric asymmetries of the atmospheric energy, favors an approximately 1° northward shift of the ITCZ. The shift of the ITCZ reorganizes atmospheric circulation, favoring a northward shift of the Hadley circulation. In addition, the Walker circulation consistently shifts westward within PlioMIP2 models, leading to wetter conditions over the northern Indian Ocean. The PlioMIP2 ensemble highlights that an imbalance of interhemispheric atmospheric energy during the mid-Pliocene could have led to changes in the dynamic effect, offsetting the thermodynamic effect and hence altering mid-Pliocene hydroclimate cycling.

The Yorktown Formation: Improved Stratigraphy, Chronology, and Paleoclimate Interpretations from the U.S. Mid-Atlantic Coastal Plain

“…With this updated age model, aside from improved control on SST data, it may be possible to obtain mollusks from within the KM5c interval for sclerochronological analyses. These analyses could shed light on seasonality and productivity from the MACP that can be integrated with a global network of existing paleoenvironmental data [5,18,[70][71][72] as well as results from seventeen PlioMIP2 paleoclimate experiments [7,[73][74][75][76][77][78][79][80][81][82][83][84][85][86][87]. [41].…”

South Asian Monsoon Variability and Arctic Sea Ice Extent Linkages During the Late Pliocene

“…While the proxy transitions during intervals IV, III, and II are captured in the composite precipitation difference, the third proxy transition between interval II and interval I is not captured in the precipitation composite difference (Figure 4c). This is likely because the model is not able to capture boundary conditions, as noted in the recent The Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) ensemble (Han et al., 2021). For example, tectonically induced changes in Indonesian Throughflow and/or South African plateaus may have resulted in SoAM intensification at 2.95 Ma (e.g., Sarathchandraprasad et al., 2021; Zhang & Liu, 2010).…”

“…Remote climate subsystems can affect SoAM by interacting both dynamically and thermodynamically. PlioMIP2 ensemble study shows that “dynamical effects” are more important than the “thermodynamical effects” in affecting the monsoonal precipitation (Han et al., 2021). The thermodynamical effect results in enhanced moisture carrying capacity due to enhanced warmth, which increases precipitation.…”

“…The jet streams meander further and influence the subtropical high over East Asia, which controls the SoAM rainfall (Chatterjee et al., 2021). The SoAM variability is controlled by the position of the Inter‐Tropical Convergence Zone (ITCZ) (Han et al., 2021). The migration of ITCZ depends on the inter hemispheric temperature contrast, which is not only governed by the seasonal insolation variability in the tropics but also by the extratropics, such as changing Arctic sea ice cover (Chiang & Friedman, 2012; Schneider et al., 2014).…”

“…of the Inter-Tropical Convergence Zone (ITCZ) (Han et al, 2021). The migration of ITCZ depends on the inter hemispheric temperature contrast, which is not only governed by the seasonal insolation variability in the tropics but also by the extratropics, such as changing Arctic sea ice cover (Chiang & Friedman, 2012;Schneider et al, 2014).…”