Sensitivity of Arctic Surface Temperature to Including a Comprehensive Ocean Interior Reflectance to the Ocean Surface Albedo Within the Fully Coupled CESM2

Almost all current climate models simplify the ocean surface albedo (OSA) by assuming the reflected solar energy without the ocean interior contribution. In this study, an improved ocean surface albedo scheme is incorporated into the Community Earth System Model version 2 (CESM2) to assess the sensitivity of Arctic surface temperature to including ocean interior reflectance to the OSA. Fully coupled CESM2 simulations with and without ocean interior reflectance are subsequently performed, we focus on the analysis of Arctic surface temperature responses. Incorporating ocean interior reflectance increases absorbed solar radiation and warms the ocean, enhancing seasonal heat storage and release across the Arctic Ocean, and increasing sea ice reduction and positive climate feedbacks that elevates Arctic surface temperature. Seasonal variations in air-surface temperature differences induce changes in turbulent heat flux patterns, concurrently modifying dynamic advection and moisture processes that affect boundary layer humidity and low clouds, especially in winter. Based on partitioning physical processes in the thermodynamic energy equation, surface air warming is induced primarily through positive heating anomalies of vertical advection, latent heat release, and longwave radiative forcing. Through an examination of the surface energy budget, skin temperature warming is driven predominantly by increased downward longwave radiation, positive surface albedo feedback in summer, and increased conductive heat transport from the ocean particularly in winter. Significant effects of ocean interior reflectance on the Arctic Ocean, including sea surface warming and sea ice reduction, justify the importance of ocean interior reflectance in climate models for better understanding of ongoing Arctic climate changes. The penetrated sunlight across the ocean surface is attenuated through the light absorption and scattering processes associated with oceanic optical constituents. The ocean attenuation of sunlight not only modifies the amount of solar energy reflected back to the atmosphere but also warms the seawater. Many climate models neglect the contribution of ocean interior reflectance to the ocean surface albedo (OSA) and hence simulate less accurate net heat flux through the air-sea interface. In this study, sensitivity simulations were performed with and without ocean interior reflectance in the OSA calculation, respectively. When ocean interior reflectance is included, the Arctic surface shows warmings in both summer and winter, and the warming is stronger in winter, due to complex feedback mechanisms in the fully coupled model. The warmer Arctic surface is predominantly caused by changes in near-surface vertical air motion, latent heat released during cloud formation, longwave radiative energy budget, and conductive heat transport from the ocean especially in winter. The changes in the drivers are related to seasonal variations in air-surface temperature differences and heat storage-release of the Arctic Ocean. To get a better understanding of climate responses associated with including ocean interior reflectance to the OSA, further investigations are necessary. Arctic surface temperature changes are simulated to better understand the implication of the ocean interior reflectance in climate modelSimulation-based increase in Arctic surface temperature is attributed to complex feedbacks inherent in the fully coupled modelClimate responses due to integrating ocean interior reflectance in the ocean surface albedo need more attention in earth system modeling