Earth Science Frontiers ›› 2022, Vol. 29 ›› Issue (4): 191-201.DOI: 10.13745/j.esf.sf.2022.1.4

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Hydrate dissociation on the northern slope of the South China Sea: Potential effects from climate warming in the current warm period

JIA Yonggang1,2,3(), RUAN Wenfeng1,3, HU Naili1,3, QIAO Yue1,3, LI Zhenghui1,3, HU Cong1,3,*()   

  1. 1. Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China
    2. Laboratory for Marine Geology, Pilot National Laboratory for Marine Science and Technology, Qingdao 266037, China
    3. MOE Key Lab of Marine Environment and Ecology, Ocean University of China, Qingdao 266100, China
  • Received:2021-09-23 Revised:2021-11-14 Online:2022-07-25 Published:2022-07-28
  • Contact: HU Cong

Abstract:

The global temperature has been rising during the current warm period (CWP, 1850-present). The rise of the bottom water temperature and sea level is affecting the stability of hydrates on the northern slope of the South China Sea. To explore the effects of the CWP climate warming on hydrate dissociation, we simulated the change of hydrate saturation during the past millennium at the shallowest depth in the hydrate reservoirs in the Dongsha, Shenhu, Xisha and Qiongdongnan sea areas, and revealed the depth range of the hydrate stability zone affected by the CWP climate warming, and discussed the extent of hydrate dissociation and its environmental impact. We showed that (1) hydrate dissociation occurred in the Dongsha, Xisha and Qiongdongnan sea areas due to the CWP climate warming, but only at water depths above 665 m, 770 m and 725 m, respectively; no hydrate dissociation observed in the Shenhu sea area. (2) Since the start of CWP, dissociated hydrates on the northern slope of the South China Sea amounted to (1.54-6.28)×1010m3, with (9.36-38.3)×107 m3 methane released. (3) The annual hydrate dissociation affected by the CWP climate warming reached (5.5-22.5)×105m3and produced (9.02-36.9)×107m3 methane. The amount of methane that reached the atmosphere was (3.61-14.8)×105m3, which accounted for 0.01%-0.06% of the annual methane contribution from human activities in China. Meanwhile, (1.77-7.23)×107 m3 methane might be oxidized to form weak acids in seawater, which worsened acidification of the northern slope of the South China Sea.

Key words: current warm period, hydrates dissociation, bottom water temperature, sea level, northern slope of the South China Sea

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