Maritime Continent Convection as a Driver of Arctic Oscillation Variability on Decadal Timescales

The Arctic Oscillation (AO) is a prominent atmospheric pattern dominating Northern Hemisphere climate variability. While its prediction is important, underlying mechanisms driving AO variability are not fully understood. Our analysis reveals that convective activity over the Maritime Continent (MC), a key tropical region straddling the equator, plays a crucial role in determining AO predictability in decadal time scale. Low-pass filtered observational data (1979–2021) shows a significant correlation (r = 0.67; 0.58 post-Nino 3.4 removal, p < 0.01) between MC convection (NOAA OLR) and the AO index. Analyses reveal that enhanced MC convection induces a Gill-Matsuno type response up to 40°N, driving a northward shift of the subtropical jet and enhancing mid-latitude potential vorticity gradient. This creates conditions for increased stratospheric wave flux, weakening the polar vortex. Pacemaker Earth system model experiments confirm this tropical-extratropical interaction mechanism. These findings demonstrate tropical influence on Arctic climate and provide new insights for AO predictability.