[A-AS21] 大気化学

[AAS21-18] 落石岬におけるAPOのトレンド変化率の年々変動とPDOの関係

*遠嶋 康徳¹、向井 人史¹、町田 敏暢¹、寺尾 有希夫¹ (1.国立環境研究所)

キーワード：APO, 大気酸素濃度, PDO, 大気二酸化炭素濃度, 大気ー海洋ガス交換

Since atmospheric potential oxygen (APO=O₂+1.1xCO₂) mainly reflects the air-sea gas exchange of O₂ and CO₂ by definition, the spatio-temporal variations in APO are expected to constrain the ocean biogeochemical process and dynamics. Here we examine the relationship between temporal variations in APO trend observed at Cape Ochi-ishi (COI; 43.2^oN, 145.5^oE) and the Pacific Decadal Oscillation (PDO) index to investigate the causes for the inter-annual variations in the APO trend. The PDO is a long-term Pacific climate variability, having two extreme phases which is classified by basin-scale patterns of the sea surface temperature (SST) anomaly. When the SST anomalies are cool in the northern North Pacific and warm in the tropical Pacific, the PDO index has positive value. And the opposite pattern of the SST anomalies correspond to the negative PDO index. The cool SST enhances the ocean vertical ventilation which brings deeper waters with depleted O₂ to the surface, causing the O₂ ingassing. The cool SST also enhances the ingassing flux by increasing gas solubility. To the contrary, the enhanced ocean vertical ventilation brings the subsurface nutrients to the surface, enhancing the O₂ outgassing through the increase in the ocean primary production. Thus, the correlation analysis between the changing rate of the APO trend (dAPO/dt) at COI and the PDO index would allow us to investigate how the SST anomaly in the northern North Pacific affect the air-sea gas exchanges. Unfortunately, there is no significant correlation between dAPO/dt and the POD index. However, when dAPO/dt and the PDO index are decomposed into the middle (0.3