Ocean Heat Transport and Water Vapor Greenhouse in a Warm Equable Climate: A New Look at the Low Gradient Paradox

• DOI: 10.1175/jcli-d-11-00547.1
• Publication Date: 2012-05-02T13:19:32Z
• Authors: Brian E. J. Rose; David Ferreira
• Keywords: Middle latitudes; Hadley cell; Extratropical cyclone

Abstract The authors study the role of ocean heat transport (OHT) in maintenance a warm, equable, ice-free climate. An ensemble idealized aquaplanet GCM calculations is used to assess equilibrium sensitivity global mean surface temperature and its equator-to-pole gradient (Δ T ) variations OHT, prescribed through simple analytical formula representing export out tropics poleward convergence. Low-latitude OHT warms mid- high latitudes without cooling tropics; increases by 1°C Δ decreases 2.6°C for every 0.5-PW increase across 30° latitude. This warming relatively insensitive detailed meridional structure OHT. It occurs spite near-perfect atmospheric compensation large imposed OHT: total nearly fixed. results from convective adjustment extratropical troposphere. Increased drives shift large-scale precipitation midlatitude storm tracks. Warming arises primarily enhanced greenhouse trapping associated with moistening upper extends poles processes even absence high-latitude A new conceptual model equable climates proposed, which plays key driving deep convection In this view, climatic impact depends on effects properties atmosphere, rather than ability energy transport.