ENSO’s changing grip on Bering Sea ice: The emerging control of the North Pacific meridional mode

Bering Sea winter sea ice (BSWI), vital for regional climate, ecosystem,
and livelihoods, is significantly influenced by El Niño-Southern
Oscillation (ENSO). Here we identify a shift in the ENSO-BSWI
relationship. Pre-mid-1990s, traditional eastern Pacific ENSO dominated,
driving a positive ENSO-BSWI linkage; Post-mid-1990s, more frequent
central Pacific (CP) ENSO events reversed this relationship to negative.
Observations and model experiments show CP El Niño coupled with
positive-phase North Pacific Meridional Mode (NPMM) redirects
poleward-propagating Rossby wave trains, enhancing Bering Sea southerlies.
This suppresses ice advection, intensifies warm air intrusion, and reduces
sea ice cover (SIC). Strengthened CP ENSO-NPMM coupling and heightened
NPMM variability amplify this teleconnection, increasing its influence on
winter SIC by 38.9% versus NPMM alone. Our findings underscore the growing
role of subtropical and tropical Pacific climate interactions in subarctic
sea ice variability and highlight the need for improved climate models
that capture ENSO diversity, NPMM dynamics, and subtropical-subarctic
teleconnections.