Physical and biogeochemical impacts of RCP8.5 scenario in the Peru upwelling system
Physical and biogeochemical impacts of RCP8.5 scenario in the Peru upwelling system
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DOI：
10.5194/bg-17-3317-2020
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发表时间：
2020-07-01
期刊：
影响因子：
4.9
通讯作者：
Colas, Francois
中科院分区：
文献类型：
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作者：
Echevin, Vincent;Gevaudan, Manon;Colas, Francois
北部洪堡洋流系统(NHCS或秘鲁上升流系统)维持着世界上最大的小型远洋渔业。虽然近几十年来在秘鲁南部海域观察到了近岸表面的降温，但关于气候变化对区域生态系统的影响仍存在相当大的争论。这就需要更准确地预测21世纪的区域气候，使用适当的工具，如区域涡旋解析耦合生物物理模型。在这项研究中，选择了来自耦合模式比较项目第五阶段(CMIP5)的三个粗网格地球系统模式(ESM)，基于它们在NHCS上游的生物地球化学偏差，对RCP8.5气候情景的模拟在NHCS中以类似于12公里的分辨率进行了动态缩小。记录了区域气候变化对温度、海岸上升流、营养物质含量、脱氧作用和浮游生态系统的影响。我们发现，缩小尺度的方法使我们能够纠正ESM的主要物理和生物地球化学偏差。所有区域模拟都显示，无论沿海上升流趋势如何，表面都会变暖。近岸海域NHCS氧最小带的演变与浮游植物的增强层结形成了鲜明对比。虽然物理参数的降低趋势与ESM趋势一致，但降低的生物地球化学趋势明显不同。这些结果表明，赤道东太平洋的ESM环流、营养场和溶解氧场需要更多的现实性，才能在NHCS的区域趋势预测中获得稳健性。
The northern Humboldt Current system (NHCS or Peru upwelling system) sustains the world's largest small pelagic fishery. While a nearshore surface cooling has been observed off southern Peru in recent decades, there is still considerable debate on the impact of climate change on the regional ecosystem. This calls for more accurate regional climate projections of the 21st century, using adapted tools such as regional eddy-resolving coupled biophysical models. In this study three coarse-grid Earth system models (ESMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) are selected based on their biogeochemical biases upstream of the NHCS, and simulations for the RCP8.5 climate scenario are dynamically downscaled at similar to 12 km resolution in the NHCS. The impact of regional climate change on temperature, coastal upwelling, nutrient content, deoxygenation, and the planktonic ecosystem is documented. We find that the downscaling approach allows us to correct major physical and biogeochemical biases of the ESMs. All regional simulations display a surface warming regardless of the coastal upwelling trends. Contrasted evolutions of the NHCS oxygen minimum zone and enhanced stratification of phytoplankton are found in the coastal region. Whereas trends of downscaled physical parameters are consistent with ESM trends, downscaled biogeochemical trends differ markedly. These results suggest that more realism of the ESM circulation, nutrient, and dissolved oxygen fields is needed in the eastern equatorial Pacific to gain robustness in the projection of regional trends in the NHCS.