North Atlantic Warming Hole Modulates Interhemispheric Asymmetry of Future Temperature and Precipitation

Abstract

The observed cooling in the subpolar North Atlantic, known as the warming hole, is receiving much attention because of its relationship with the climate sensitivity in the Earth System Models (ESMs). However, the impact of its future projection on the global climate remains unclear due to large uncertainties. Here, we show that the future warming hole changes will affect the interhemispheric asymmetry of temperature and precipitation by modulating the Northern Hemisphere (NH) warming. Models with a weaker warming hole in the future project stronger NH warming by injecting more non-radiative fluxes to the atmosphere. This leads to an asymmetric warming contrast between the two hemispheres, resulting in a meridional shift of the Inter-Tropical Convergence Zone and more precipitation increases in the NH. Our study implies that the future warming hole controls the interhemispheric heat exchanges and associated changes in the global temperature and precipitation, suggesting that its improved simulation is essential. The simulation of future warming hole intensity remains a major uncertainty in the Earth system models (ESMs) and its climatic impact is unclear. Here, using the ESMs, we show that future changes in the warming hole cause the interhemispheric asymmetry of temperature and precipitation. The warming of the warming hole injects non-radiative fluxes into the atmosphere, amplifying more warming in the Northern Hemisphere than the Southern Hemisphere. Concurrently, this creates an energy imbalance between two hemispheres that leads to a northward shift of the Inter-Tropical Convergence Zone, resulting in the interhemispheric asymmetry of precipitation. Future warming hole changes in Coupled Model Intercomparison Phase 6 models affect the interhemispheric asymmetry of temperature Greater warming in the warming hole increases the non-radiative fluxes in the Northern Hemisphere, leading to an increase in the interhemispheric asymmetry The warming hole affects future global precipitation by modulating the location of the ITCZ