Secular trends and seasonal variations of partial pressure of carbon dioxide in the surface sea water in the Australian secutor of the Southern Ocean

In order to elucidate the secular trends of oceanic CO_2 uptake in the Indian sector of the Southern Ocean, pCO_2, the partial pressure of CO_2 in the ocean surface layer, has been measured since 1987 on board the icebreaker Shirase. Meridional distributions of pCO_2 along 110゜E in early December cl...

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Bibliographic Details
Main Authors: Gen Hashida, Shin-ichiro Nakaoka, Hisashi Ono, Takakiyo Nakazawa, Hisayuki Yoshikawa, Shuji Aoki, Shinji Morimoto, Takashi Yamanouchi, Tsuneo Odate, Mitsuo Fukuchi
Format: Article in Journal/Newspaper
Language:English
Japanese
Published: National Institute of Polar Research 2010
Subjects:
Online Access:https://doi.org/10.15094/00009566
https://doaj.org/article/579c3e5e33ba4949883bceefb2672fc5
Description
Summary:In order to elucidate the secular trends of oceanic CO_2 uptake in the Indian sector of the Southern Ocean, pCO_2, the partial pressure of CO_2 in the ocean surface layer, has been measured since 1987 on board the icebreaker Shirase. Meridional distributions of pCO_2 along 110゜E in early December clearly show steep changes at such fronts as the subtropical front, subantarctic front, and polar front. Although pCO_2 of each zone shows interannual variation, secular trend is detectable. For example, the estimated rate of increase of pCO_2 in the permanent open ocean zone between the polar front (around 53゜S) and the northern edge of winter ice cover (63゜S) is about 1.3 μatm y, which is slightly lower than the rate of increase of the atmospheric CO_2 concentration. From the results obtained by multi-ship observations with 4 research vessels in the Southern Ocean in summer, we found that the values of pCO_2 off the coast of the Antarctic Continent (66゜S) varied temporally by 100 μatm for 5 months. We also found that nDIC decreased with time from December 2001 to March 2002 in the upper layer from 100 to 200 m due to biological activity during summer.