Asymmetry in the effect of North Atlantic sea surface temperature on the eddy‐driven jet

Future changes in North Atlantic sea surface temperatures (NASST) are uncertain. We assess how different future changes in NASST can affect the eddy‐driven jet and the atmospheric circulation over the North Atlantic and Western Europe. We use a set of atmosphere‐only simulations and show that NASST warming results in a negative North Atlantic Oscillation (NAO) phase, decreased European storm activity, and an equatorward shift of the eddy‐driven jet. The response to the NASST anomaly is asymmetric, with the warming of the NASST affecting the winter season while the cooling of the NASST only affects the late winter season (poleward shift of the eddy‐driven jet and positive phase of the NAO). We link the subseasonal asymmetry to troposphere–stratosphere interactions. The warming of the NASST strongly affects the troposphere, while the cooling of the NASST has a substantial impact on the stratosphere, with anomalies that are at the surface in late winter. In addition, we demonstrate that the change in subpolar gyre temperature affects the North Atlantic climate but contributes only moderately to the asymmetric response.