The partitioning of the poleward heat transport between the ocean and the atmosphere

Observations of the poleward heat transport of the Earth (H) suggest that H is dominated by the contribution of the atmosphere at latitudes poleward of 30 degrees, while both oceanic (HO) and atmospheric (HA) contributions are important in the equatorial belt, with the ocean dominating in the deep Tropics.

To study the partition we express the ratio HA / HO as

HA / HO = PSIA/PSIO * (CA*DTA/CO*DTO) (1)

where PSIA, PSIO represent the strengths of the meridional mass transports in the respective fluids, CA, CO are their heat capacities, DTA is a typical vertical difference in moist potential temperature over the tropopause and DTO is a measure of the potential temperature change across the thermocline.

We argue that the observed partition of heat transport between atmosphere and ocean is a robust feature of the Earth climate and reflect two limits of Eq.(1):

(i) a dominance of atmospheric mass transport in mid-to-high latitudes, i.e. HA/ HO ~ PSIA / PSIO >> 1

(ii) a dominance of oceanic stratification in the Tropics, i.e. HA / HO ~ CA*DTA /CO*DTO << 1

Motivated by simple dynamical arguments, these ideas are tested against the NCEP-NCAR reanalysis, and a long simulation of a coupled atmosphere-ocean model of intermediate complexity.