Centre for in situ Observational Oceanography

Seasonally Low Oxygen Values and Warmer Bottom Temperatures

In an investigation done by Eagle and Orren (1985) on nutrients and dissolved oxygen on the Agulhas Bank, they found that occasionally a pocket of low-oxygen water was found near the bottom. No clear seasonal pattern was indicated, although it occurred predominantly in autumn. Eagle and Orren suggested that this low-oxygen water could be associated with a layer of high turbidity water (refer to Figure 1).

Seaonally low bottom oxygen values and warmer bottom temperatures  

Figure 1
Time series of dissolved oxygen fluctuations on the Agulhas Bank, 1974-1979. (Diagram reproduced and altered from Eagle and Orren, 1985).


Warmer bottom waters were recorded during the summer months. Deepening of the upper mixed layer occurs in winter (July to October). Sporadic intrusions of bottom cold water also occur (Eagle and Orren, 1985) (refer to Figure 2).

Seaonally low bottom oxygen values and warmer bottom temperatures  

Figure 2
Time series of temperature fluctuations on the Agulhas Bank, 1974-1979. (Diagram reproduced and altered from Eagle and Orren, 1985).



CLASSIC PAPER

Eagle, G. A. and Orren, M. J. (1985).
A seasonal investigation of the nutrients and dissolved oxygen in the water column along two lines of stations south and west of South Africa.
CSIR Research Report 567.