Seasonal variation of surface water CO2 partial pressure in the Southland Current, east of New Zealand

Abstract

The partial pressure of CO₂ in the surface waters (pCO₂^sw) of the Southland Front east of New Zealand was determined over one annual cycle in 1992/93. Associated parameters of temperature, salinity and nutrients were also measured. Both the modified subtropical waters of the Southland Current and the cooler subantarctic surface waters were undersaturated with CO₂ with respect to the atmosphere. The maximum ΔpCO₂ of –150 µatm was measured in April 1993. A simple model taking into account the effects of temperature, biological activity and air–sea exchange applied to subantarctic surface water indicated that at different times of the year changes in sea surface temperature, biological activity and mixing processes are the dominant controls of pCO₂^sw .