The circulation response to Arctic Amplification in zonally symmetric and asymmetric aquaplanets

This study investigates the impact of Arctic Amplification (AA) on midlatitude temperature extremes using aquaplanet simulations within the ISCA intermediate complexity modeling framework. We use a mixed-layer ocean as boundary condition and grey radiation. Simulations are run with two setups: a zonally symmetric control and a zonally asymmetric experiment. In the asymmetric experiment a localized oceanic heating is prescribed in the midlatitudes to mimic a western boundary current and generate a eddy transient kinetic energy maximum (or storm track). For each setup, we run simulations without and with AA, whereby anomalous heating is imposed in the northern polar region.

We investigate the autocorrelation of local wave activity (LWA) in our experiments, as this allows us to focus on persistent LWA regimes, which can be linked with temperature extremes such as heatwaves and cold spells. We find that the autocorrelation maxima in the asymmetric configuration correlate with well known atmospheric patterns such as atmospheric blocking, demonstrating that our model setup, despite its simplicity, can reproduce realistic features of Earth’s atmospheric circulation. Early results show how the LWA autocorrelation slightly increases with AA in the zonally symmetric setup, and decreases with AA in the zonally asymmetric setup, indicating that the sign of the change depends on the zonal symmetry. This suggests that the LWA climatology, highly sensitive to the presence of a storm track region, plays a crucial role in the atmospheric response to AA.