Increasing Atlantic Ocean Heat Transport in the Latest Generation Coupled Ocean‐Atmosphere Models: The Role of Air‐Sea Interaction

• Published in: Journal of geophysical research. Oceans 2018-11, Vol.123 (11), p.8624-8637
• Main Authors: Grist, Jeremy P., Josey, Simon A., New, Adrian L., Roberts, Malcolm, Koenigk, Torben, Iovino, Doroteaciro
• Format: Article
• Language: English
• Subjects: Air-sea interaction; Atlantic ocean; Atmosphere; Atmospheric models; Cells; Climate; Climate models; Climate system; Components; Computer simulation; Earth; Environmental modeling; Exports; Geophysics; Heat; Heat exchange; Heat flux; Heat loss; Heat transfer; Heat transport; Latitude; model resolution; Northern Hemisphere; ocean heat transport; Ocean models; Oceans; Regions; Resolution; Sea surface; Sea surface temperature; surface fluxes; Surface temperature; Temperature; Temperature (air-sea); Transport; Tropical environments; Vortices
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2018JC014387

Recent increases in resolution of coupled ocean‐atmosphere models have the potential to improve the representation of poleward heat transport within the climate system. Here we examine the interplay between model resolution‐dependent changes in Atlantic Ocean heat transport (AOHT) and surface heat fluxes. The different roles of changes in atmospheric and ocean resolution are isolated using three different climate models (The Centro Euro‐Mediterraneo sui Cambiamenti Climatici Climate Model 2, Hadley Centre Global Environmental Model 3 – Global Coupled configuration 2, and European Community Earth‐System Model 3.1) and comparing runs in which (a) only the ocean resolution changes, (b) only the atmosphere resolution changes, and (c) both change. Enhancing ocean resolution from eddy parameterized to eddy permitting increases the AOHT throughout the basin, values changing from 1.0 to 1.2 PW at 26°N, bringing the AOHT into the range of estimates from the RAPID observing array. This increase in AOHT is associated with higher North Atlantic sea surface temperatures and increased ocean heat loss to the atmosphere. Increasing the atmospheric resolution alone has little impact on the AOHT due to regionally compensating changes in the components of the net heat flux. Finally, in a fourth experiment the impact of resolution changes in both components and the transition to an eddy‐resolving ocean is assessed. This additional resolution increase is accompanied by a further change in the AOHT and improves agreement with observations in the tropics but not the subpolar regions. However, unlike with the increase to the eddy‐permitting ocean, when the greatest AOHT change occurs in the subtropics and subpolar region, the most significant increase now occurs in the tropics. Plain Language Summary The ocean and atmosphere export large amounts of heat from the tropics toward more poleward latitudes. In the Northern Hemisphere about 25% of this export is accomplished by the movement of water in the Atlantic Ocean. It is therefore important for climate models to accurately simulate this Atlantic Ocean heat transport (AOHT). However, historically climate models have typically underestimated AOHT relative to our best observations. This paper investigates how changing the size of the grid cells in the model changes both AOHT and the ocean‐to‐atmosphere exchange of heat in the model. Reducing the size of the grid cells in the models is referred to as increasing the resolution. Increa