Variations of oceanic pCO₂ and air‐sea CO₂ flux in the eastern Indian sector of the Southern Ocean for the austral summer of 2001–2002

Abstract

We examined pCO2air and pCO2sea observed in the eastern Indian sector of the Southern Ocean (south of 50°S, 140°–150°E) during austral spring‐summer from November 2001 to March 2002 using 4 research vessels. pCO2sea changed by as much as 200 μatm over the 5‐month period in the Seasonal Sea Ice Zone (SSIZ), due mostly to very low values in January caused by stratification of water column and strong biological activity. In the SSIZ, the air‐sea CO2 flux showed large temporal variations, from −2.9 g m−2 month−1 in January 2002 to −0.65 g m−2 month−1 in February 2002. The monthly oceanic CO2 uptake in the area covered by this study (1.5 × 1012 km2) was estimated to be in a range of 1.0 × 10−3 to 1.7 × 10−3 PgC month−1, with a mean value of 1.3 × 10−3 PgC month−1.

Winter-to-summer evolution of <i>p</i>CO<sub>2</sub> in surface water and air–sea CO<sub>2</sub> flux in the seasonal ice zone of the Southern Ocean

“…9a). Our F CO 2 (a−w) (0.0 to +0.9 mmol C m −2 day −1 ) falls within the range (−8.2 to +7.2 mmol C m −2 day −1 ) reported in previous studies in the SIZ (Bakker et al, 1997;Metzl et al, 1999Metzl et al, , 2006Chierici et al, 2004;Nakaoka et al, 2009).…”

“…During the cruise, pCO 2 in surface water was evaluated through the underway water measuring system (Inoue and Ishii, 2005;Nakaoka et al, 2009). CO 2 concentration (mole fraction of CO 2 in dry air; xCO 2 ) was measured quasicontinuously in the air equilibrated with seawater using an automated CO 2 measuring system (Nippon ANS Co. Ltd., Tokyo, Japan).…”

Winter to summer evolution of <i>p</i>CO<sub>2</sub> in surface water and air–sea CO<sub>2</sub> flux in the seasonal ice zone of the Southern Ocean

“…9a). Our F CO 2 (a−w) (0.0 to +0.9 mmol C m −2 day −1 ) falls within the range (−8.2 to +7.2 mmol C m −2 day −1 ) reported in previous studies in the SIZ (Bakker et al, 1997;Metzl et al, 1999Metzl et al, , 2006Chierici et al, 2004;Nakaoka et al, 2009).…”

Response of sea surface fugacity of CO2 to the SAM shift south of Tasmania: Regional differences

“…To reduce uncertainty in the trend analysis due to spatial variability and to examine regional differences in f CO 2 changes, we divided the study area from north to south into three zones according to the positions of the main circumpolar fronts (Figure ), i.e., the Subantarctic Zone (SAZ) between the Subtropical Front (STF) and the Subantarctic Front (SAF), the Polar Frontal Zone (PFZ) between the SAF and the Polar Front (PF), the Polar Zone (PZ) between the PF and 62°S [ Yoshikawa‐Inoue and Ishii , ]. The positions of the STF, SAF, and PF were determined based mainly on SSS gradients [ Chaigneau and Morrow , ], since surface data were relatively easily available, and f CO 2 changes at the surface were focused on [ Midorikawa et al ., ; Nakaoka et al ., ; Yoshikawa‐Inoue and Ishii , ]. The specific position of each front was shown in Table S1 and Figure S1. In addition, to reduce errors due to different sampling intervals, for each parameter (including SST, SSS, and sea surface f CO 2 ) we first binned all the data points into their respective 0.02° latitudinal bands, then calculated the average for each band, and finally took an average at each zone as in Xue et al .…”