Schematic of the proposed cross-basin atmospheric bridge linking La Niña and Southern Indian Ocean warming to Arctic sea ice loss (IMAGE)
Caption
Schematic diagram illustrating the combined pathways by which cold sea surface temperature (SST) anomalies in the tropical central-east Pacific (TCEP; blue rectangle) and warm SST anomalies in the South Indian Ocean (SIO; red rectangle) drive sea ice reduction in the Okhotsk and Bering Seas (yellow rectangle). The TCEP cold SST anomaly enhances the Walker Circulation (blue dashed arrows), causing anomalous downward motion over the tropical Indian Ocean, which subsequently triggers a Rossby wave train (gray arrows) that induces an anomalous anticyclone over the Sea of Okhotsk (light purple semicircle). In parallel, the SIO warm SST anomaly generates local ascent, driving an anomalous Hadley Cell (red dashed arrows); the resultant downward motion anomalies over the tropical Indian Ocean further reinforce the similar Rossby wave train (gray arrows), thereby strengthening the Okhotsk anticyclone (light purple semicircle). These synergistic anticyclonic anomalies over the Okhotsk and Bering Seas create atmospheric conditions conducive to sea ice melt. Anticyclones and cyclones are denoted by purple and green circles, marked “AC” and “C”, respectively.
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