[M-IS08] 南大洋・南極氷床が駆動する全球気候変動

[MIS08-16] Rapid progress of ocean acidification over the Southern Ocean

*李 勃豊¹、潘 先亮¹、渡辺 豊¹ (1.北海道大学)

キーワード：南大洋、海洋酸性化、人為起源二酸化炭素

The Southern Ocean (SO, south of 30°S) covers 30% of the global ocean surface area and is presumed to account for 40% of the global ocean's anthropogenic CO₂ (DIC_anth) absorption as shown by numerical modeling calculations. This may lead to intensive anthropogenic acidification in the SO. Clarifying the ocean dynamics of the anthropogenic component of the carbon system in the SO is crucial for gaining a deep understanding of the human impact on the ocean. However, natural processes also influence the change in ocean pH. Distinguishing anthropogenic and natural components from the observed dissolved inorganic carbon (DIC) and pH is essential for clarifying the acidification in the SO. Here we separated the anthropogenic and natural components by combining new parameterization techniques with high-resolution grid data constructed based on ship-based observations. The change of DIC_anth inventory during the 1990s-2010s, showed that anthropogenic effect on DIC accounted for 62% of the total change of DIC, which was comparable to 11% of the global emission amount of CO₂ due to human activities. Ocean acidification derived from this DIC_anth covered most of the surface and intermediate depths by 3,500 m over the SO, and the maximum decreasing rate of anthropogenic pH was 0.004 pH year^–1 as twice decreasing of the global average.