南半球环状模对西南极半岛海域水团动力过程和分布特征变异的影响与机制

The western Antarctic Peninsula (WAP) region is a major area for the Chinese Antarctic krill fishing activities. The circumpolar deep water, ice shelf melt water and surface water play a significant role in modulating the heat content, the density structure and the primary production in this region. WAP is also one of the areas that have experienced the strongest climate variation near Antarctica, and its climate variability is significantly affected by the Southern Annular Mode (SAM). In previous studies, the response of atmosphere, sea-ice and large-scale ocean circulations including the Antarctic Circumpolar Current (ACC) to the SAM variability have been extensively discussed for the WAP region, but the relations between SAM and the water mass dynamics and distributions, which are considerably affected by the atmospheric and ACC processes, have not been well understood. Based on multi-year ecological data and numerical simulations, we found evidence that indicate a significant correlation between the interannual variability of the water masses and the variability of SAM. Inspired by this, this study aims to fully uncover the relation of the variations in the water mass dynamics and distributions to the variation of SAM on interannual and decadal timescales, to find out the major mechanisms for SAM to work on the water mass variability, and to project the future trend of water mass variations with SAM. Long-term observational data and numerical simulations will be combined in our investigations, and the outcome of this work are expected to further our understanding of the long-term evolutions of the dynamical and ecological systems in the WAP area and the underlying forcing mechanisms.

西南极半岛海域是我国南极磷虾资源开发的主要区域。其内的绕极深层水、冰架融水和表层水不仅是该海域热含量和密度结构的重要影响因素，同时也是初级生产力的关键调控因子。西南极半岛同时也是南极气候变化最为强烈的区域之一，受到南半球环状模（SAM）变异的显著影响。在以往研究中，该区域的大气、海冰过程和南极绕极流对SAM变异的响应特征已经得到了广泛探讨，而受这些因素影响的中尺度水团运动和分布过程同SAM变异存在何种关系目前尚不明确。通过对多年生态学数据的深入挖掘和对数值模拟结果的初步分析，我们发现以上几种水团的运动和分布可能同SAM在年际变异上存在显著相关。因此，本项目将进一步结合长期观测资料和数值模拟结果，充分揭示上述水团的年际、年代际变异特征同SAM的关系，阐释SAM对水团变异的作用机制，预估未来水团随SAM的变异趋势，以期深入理解研究海域动力环境和生态系统的长期发展规律和机理。

西南极半岛海域是我国南极磷虾资源开发的主要区域。其内的绕极深层水（Circumpolar Deep Water, CDW）、冰架融水和表层水不仅是该海域热含量和密度结构的重要影响因素，也是初级生产力的关键调控因子。西南极半岛同时也是南极气候变化最为强烈的区域之一，受到南半球环状模（SAM）变异的显著影响。该海域中尺度水团运动和分布过程是否受制于SAM的调控尚不明确，进而制约了对水团变化规律与机理的认识。本项目结合长期现场观测资料、卫星遥感数据、高分辨率海洋-海冰-冰架耦合模式的模拟结果和大气再分析数据，揭示了研究区域关键水团的年际变异同SAM变化的关系，阐释了SAM对水团变异的作用机制，预估了水团随未来SAM变异的变化趋势，同时探究了水团变化对生态系统浮游植物量的影响。项目取得的主要成果包括：（1）南设得兰群岛和象岛附近海域CDW向陆架入侵及在陆架分布范围的年际变化同SAM存在显著关联，主要机制为SAM向正位相发展时西风增强，增强了CDW在陆坡区的涌升活动及其向陆架的水平入侵；同时，西风增强增加了海洋垂直混合强度，CDW和混合的变化使得该区域浮游植物量年际变化同SAM也呈现显著相关性；（2）在西南极半岛生物热点区之一玛格丽特湾冰间湖，春季SAM的变异会通过影响风场、暖湿气流的输运和降水影响海洋表层水盐度，改变上层海洋层化，最终对于夏季浮游植物量产生影响；（3）基于CMIP6的SSP585未来气候情景，本项目发现伴随西风的增强，CDW向阿蒙森海陆架的入侵活动会增强，并导致陆架海域温度上升和冰架融水生成量的增加，研究对冰架融水生成速率进行了定量预估。本项目推动了对西南极半岛海域动力环境和生物生产力在年际以上时间尺度变化规律和机理的认知。