From Thermodynamics to Dynamics: The Victoria Mode Reshapes Pacific Side of the Arctic Winter Sea Ice Growth

Despite widespread Arctic sea ice loss under global warming, early winter sea ice growth (SIG) in the Pacific side of the Arctic has displayed amplified interannual variability since 2007 —a phenomenon whose underlying mechanisms remain unclear. We show that this amplification is primarily linked to a strengthened influence of the North Pacific's Victoria Mode (VM), operating through a dynamic pathway rather than local thermodynamic processes. Observations reveal that the post‐2007 intensification and structural reorientation of the VM excites an eastward‐propagating Rossby wave train, which establishes an anticyclonic anomaly over the Eurasian sector of the Arctic. This atmospheric reconfiguration alters wind‐driven ice drift, enhancing ice divergence toward the northwestern Beaufort Gyre and thereby dynamically amplifying SIG variability. Sea ice concentration budget analysis confirms that while thermodynamic processes dominate the mean‐state SIG, the amplification of interannual variability post‐2007 is attributable to this dynamic mechanism. Model experiments forced by VM SST anomalies reproduce the observed atmospheric response, establishing causality. Our findings reveal a regime shift in Pacific–Arctic linkages, with potential implications for seasonal forecasts and long‐term projections of Arctic sea ice.