Fast and slow responses of the Subantarctic Mode Water in the South Indian Ocean to global warming in CMIP5 extended RCP4.5 simulations
Fast and slow responses of the Subantarctic Mode Water in the South Indian Ocean to global warming in CMIP5 extended RCP4.5 simulations
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CMIP5 扩展 RCP4.5 模拟中南印度洋亚南极模式水对全球变暖的快速和慢速响应
DOI：
10.1007/s00382-021-05635-w
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发表时间：
2021-01
期刊：
影响因子：
4.6
通讯作者：
Yan Du
中科院分区：
文献类型：
--
作者：
Xingyue Xia;Lixiao Xu;Shang-Ping Xie;Yu Hong;Yan Du
本研究基于耦合模式比对项目第5阶段（CMIP5）扩展模拟，在代表性浓度路径4.5 （RCP4.5）下，研究了南印度洋（SIO）亚南极模态水（SAMW）的长期演变。在2000 - 2100年的快速辐射强迫增长期，SIO的SAMW迅速缩小和变薄。2100年以后，当辐射强迫趋于稳定时，SAMW缓慢扩大和增厚。SAMW的响应既取决于地表浮力的演变，也取决于上覆西风应力的变化。2000-2100年，地表热通量主导了SAMW形成区的净浮力增益，而西风的增强则由于其向极移动而在较小程度上起作用。2000 - 2100年，随着辐射强迫的快速增加，SAMW形成区的浮力增加导致混合层的快速浅化和SAMW俯冲速率的降低。地表增温增强了分层，减少了以低位涡量（PV）水体积量化的SAMW。因此，SAMW迅速收缩和变薄。2100年以后，当辐射强迫趋于稳定时，地下增温大于地表，伴随的缓慢脱层逐渐增加了低PV水量。因此，SAMW膨胀和增厚缓慢。SAMW的快速和缓慢反应对SIO的热吸收和循环具有重要意义。
The present study examines the long-term evolution of the Subantarctic Mode Water (SAMW) in the south Indian Ocean (SIO) based on the Coupled Model Intercomparison Project Phase 5 (CMIP5) extended simulations through 2300 under Representative Concentration Pathways 4.5 (RCP4.5). The SAMW in the SIO shrinks and thins rapidly during the fast radiative forcing increasing period between 2000 and 2100. After 2100, when the radiative forcing stabilizes, the SAMW expands and thickens slowly. The response of SAMW is dependent both on the evolution of surface buoyancy forcing and overlying westerly wind stress. During year 2000–2100, the surface heat flux dominates the net buoyancy gain over the SAMW formation region, whereas the enhanced westerly wind contributes to a lesser extent due to its poleward shift. As the radiative forcing increases rapidly from 2000 to 2100, the buoyancy gain over the SAMW formation region results in a fast shoaling mixed layer and a reduction in the SAMW subduction rate. The surface intensified warming enhances stratification and reduces the SAMW that is quantified by the volume of low potential vorticity (PV) water. Consequently, the SAMW shrinks and thins fastly. When the radiative forcing stabilizes after 2100, the warming is greater in the subsurface than the surface, and the associated slow destratification gradually increases the low PV water volume. Hence, the SAMW expands and thickens slowly. The distinct fast and slow responses of SAMW have implications for the heat uptake and circulation of the SIO.
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