Zhang Min, Cheng Yangyan, Zhang Haoyu, Huang Chuanjiang, Wang Gang, Zhao Chang, Zhang Yuanling, Yang Qinghua, Song Zhengya, Qiao Fangli
First Institute of Oceanography and Key Laboratory of Marine Sciences and Numerical Modelling, Ministry of Natural Resources, Qingdao, 266061, China; Laboratory for Regional Oceanography and Numerical Modelling, Qingdao Marine Science and Technology Center, Qingdao, 266237, China; Shandong Key Laboratory of Marine Sciences and Numerical Modeling, Qingdao, 266061, China.
School of Marine Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519082, China.
Mar Environ Res. 2025 Feb;204:106949. doi: 10.1016/j.marenvres.2025.106949. Epub 2025 Jan 3.
The tropical Pacific is the largest oceanic source of carbon dioxide (CO) emissions, where persistent marine heatwaves (MHWs) frequently occur. During persistent MHW events which are associated with strong El Niño events, CO outgassing is notably reduced, however, its detailed spatiotemporal response to MHWs has not been fully characterized. In this study, we showed a high degree of consistency between CO source regions in the central and eastern tropical Pacific Ocean and the occurrence regions with average annual MHW days exceeding 45 days (co-occurring area covers 80% of the area where MHWs occur). The spatiotemporal variability of the air-sea CO flux on interannual and longer timescales can be reconstructed from annual MHW days and occurrence frequency, respectively, in the central and eastern Pacific Ocean of the co-occurring region. In this region, El Niño-related MHWs reduce the air-sea CO flux density up to 0.4-0.8 molC/m/yr per 100 MHW days, corresponding to a reduction of CO emissions by approximately 0.1 PgC per 100 MHW days. This is a 10%-40% reduction in CO emissions during MHW periods, with the strongest impact (30%-40% CO emission reduction) in the equatorial Pacific (5°S-5°N) of the central and eastern Pacific Ocean. In contrast, air-sea CO flux variations in coastal eastern upwelling region of the co-occurring region are mainly subjected to seasonal mixed layer variations, and thus not notably affected by El Niño-related MHWs on interannual timescales. By establishing the reproducibility between MHWs and air-sea CO flux variations, our results pave a way for detailed future spatiotemporal evolutions of MHW-induced changes in air-sea CO flux in the tropical Pacific Ocean.
热带太平洋是最大的海洋二氧化碳（CO）排放源，这里经常出现持续性海洋热浪（MHW）。在与强厄尔尼诺事件相关的持续性MHW事件期间，CO的脱气明显减少，然而，其对MHW的详细时空响应尚未得到充分表征。在本研究中，我们发现热带中东太平洋的CO源区与年平均MHW天数超过45天的发生区域之间具有高度一致性（共现区域覆盖了MHW发生区域的80%）。在共现区域的中东太平洋，海气CO通量在年际和更长时间尺度上的时空变化分别可以从年MHW天数和发生频率重建。在该区域，与厄尔尼诺相关的MHW每100个MHW天数可使海气CO通量密度降低0.4 - 0.8 molC/m²/yr，相当于每100个MHW天数减少约0.1 PgC的CO排放。这是MHW期间CO排放量减少10% - 40%，在中东太平洋赤道地区（5°S - 5°N）影响最强（CO排放量减少30% - 40%）。相比之下，共现区域东部沿海上升流区的海气CO通量变化主要受季节性混合层变化影响，因此在年际时间尺度上不受与厄尔尼诺相关的MHW显著影响。通过建立MHW与海气CO通量变化之间的可重复性，我们的结果为未来详细研究热带太平洋中海气CO通量因MHW引起的时空演变铺平了道路。
