North Atlantic circulation regimes and heat transport by synoptic eddies

Meridional transport of heat by transient atmospheric eddies is a key component of the energy budget of the middle and high latitude regions. The heat flux at relevant frequencies is also part of a dynamical interaction between eddies and mean flow. In this study we investigate how the poleward heat flux by high frequency atmospheric transient eddies is modulated by North Atlantic weather regimes in reanalysis data. Circulation regimes are estimated via a clustering method, a jet latitude index and a blocking index. Heat transport is defined as advection of moist static energy. The focus of the analysis is on synoptic frequencies but results for slightly longer time scales are reported. Results show that the synoptic eddy heat flux is substantially modulated by mid-latitude weather regimes on a regional scale in midlatitude and polar regions. On a zonal mean sense, the phases of the North Atlantic Oscillation do not change significantly the high latitude synoptic heat flux, whereas Scandinavian blocking and Atlantic Ridge are associated with an intensification. A close relationship between high (mid) latitude heat flux and Atlantic jet speed (latitude) is found. The relationship between extreme events of synoptic heat flux and circulation regimes is also assessed and reveals contrasting behaviours in polar regions. The perspective that emerges complements the traditional view of the interaction between synoptic eddies and the extra-tropical flow and reveals relationships with the high latitude climate.