The transition from
primarily bucket measurement in 1970 to primarily engine inlet in 2000 was supported by the following graphic in Kent et al 2007 discussed in last year's posts e.g. here:
These effects have been quantified; for example engine room intake (ERI) temperatures have been compared to
bucket measurements by a number of studies.
I'm assuming there's no way to know if boat -
bucket measurements were conducted in eddy anomalies back - in - the - day.
The switch from canvas to insulated buckets occurred concurrently with changes in the balance of engine intake and
bucket measurements.
The change in country of origin in August 1945 is important for two reasons: first, in August 1945 US ships relied mainly on engine room intake measurements whereas UK ships used primarily uninsulated
bucket measurements, and second, engine room intake measurements are generally biased warm relative to uninsulated bucket measurements.