As I said in a previous post the sea surface temperature close to the
Arctic have gone from a strong +'ve annomally that has been there for
about 2 years to areas of -'ve annomally. Is this a change in phase of
some sort?

Often with the Sea Surface Temperature annomalies are caused by an
obvious mechanism. For example the western Atlantic at the moment
after all the Hurricanes and tropical storms this season.

However I cannot see an obvious mechanism for this dramatic change in
these northern areas.

See link below:

https://www.fnmoc.navy.mil/products/...sstanomaly.gif