Heats tags demonstrate how remote latent heating controls the heat content of the Arctic Atmosphere

Abstract:

The large amounts of latent heating in the storm tracks and Tropics are balanced in part by the longwave cooling occurring in the Arctic. This implies that there must be a transport of warm air masses from the tropics and midlatitudes into the Arctic. This transport, and its contribution to Arctic heat content, can be diagnosed using heat tags: passive tracers that record the heat content from a given diabatic process like convection, large-scale condensation, or diffusive heating.

Using an idealized aquaplanet model, we find that the warm air masses created through latent heating outside the poles contribute between 50% and 70% of the dry static energy (potential temperature) within the polar troposphere. Additionally, warm air masses created by extrapolar latent heating are responsible for a significant fraction of the variance of potential temperature in the polar midtroposphere.

In a CO2 doubling experiment, there is polar amplification in the surface temperature response, even though the aquaplanet model lacks sea ice. The heat tagging analysis shows that this polar amplification results from increased latent heating and transport from remote latitudes. The results show the importance of the global hydrological cycle in maintaining the heat content of the polar regions, and the importance of remote latent heating in understanding polar amplification.