What is the most immediate threat stemming from the narwhal's strict reliance on sea ice?

Answer

The sea ice forming later, melting earlier, and becoming thinner

The most immediate threat is the instability of the sea ice, which is forming later, melting earlier, and becoming thinner due to rising Arctic temperatures, disrupting their millennia-old migratory patterns.

What is the most immediate threat stemming from the narwhal's strict reliance on sea ice?
animalTuskNarwhal