IS PHOSPHATE PART OF THE RUSSELL CYCLE

The evidence for variations in winter phosphate concentration as a com ponent of the 'Russell Cycle' has been re-examined. The change from hi gh phosphate concentrations prior to 1930 is the largest apparent vari ation in concentration through the period 1923-1987. However, these va lues are the result of a retrospective application in 1938, of a salt correction factor of 1.35. The justification for this factor is examin ed. It is concluded that there is sufficient uncertainty in the accura cy of the pre-1948 measurements of phosphate concentration to preclude their use in long time-series analysis. A statistical analysis of the post-1948 data shows that a simple first order autoregression model p rovides a perfectly adequate description of the data; the data can be considered as essentially random, with a small component of carry over from one year to the next. The evidence is weak that variations in wi nter concentrations of phosphate support the Russell Cycle hypothesis.