A time series transect has been established in
subantarctic surface water off the south east coast of New Zealand. The 60 km long transect extends from the
coast (45-46.20oS 170-43.20oE) to a station at 45-50.00oS
171-30.00oE. and sea surface temperature, salinity and pCO2
have been measured bi-monthly since 1998 . SST, pCO2 and pH of the
subantarctic surface water show seasonal cycles that can be fitted with simple
harmonic curves. Temperature has a mean
value of 10.4oC, with an amplitude of 2.1oC, the maximum
occurring in late summer. pCO2
has a mean value of 360 matm, an amplitude of 10 matm, the maximum occurring in early
spring. The phase of the pCO2
and temperature curves are offset by 158 days, indicating that change in sea
water temperature is not the major factor affecting pCO2 in this
area. The relative effects of
temperature, biological utilization and air-sea gas exchange on the seasonal
change in pCO2 are determined using a simple model. The model results reproduce the timing of the
observed pCO2, however the amplitude of the changes is not well
reproduced.
Author: K.I. Currie and M.R. Reid (k dot currie at niwa dot co dot nz)
Filesize: 36.14 Kb