On: An annual blast of Pacific cold water did not occur

[tokai]

Its a common word used for large areas of ocean water of anomalous temperature.

https://en.wikipedia.org/wiki/The_Blob_(Pacific_Ocean)

https://en.wikipedia.org/wiki/Cold_blob

Blob is perfectly good word, and much more precise in this case than 'mass'.

[thimkerbell → tokai]

Depends on the audience maybe.