EAGER: Ocean Circulation in the Amundsen Sea Embayment over the 20th Century

西南极阿蒙森海湾的冰川，如斯韦茨冰川和松岛冰川，正在迅速消退，导致海平面上升。有证据表明，目前的退缩阶段始于20世纪中叶，当时还没有开始观测记录，因此很难理解冰川变化的原因。虽然模拟研究表明，从20世纪初开始的人为强迫导致了更强的西风条件的趋势，从而导致冰川附近的海洋条件变暖，但自20世纪初以来的新的基于代理的风速重建提供了强有力的证据，表明该地区的风向可能是东风而不是西风。这个项目将利用海洋模型来研究20世纪的东风趋势是否会导致阿蒙森海冰川附近的海洋条件变暖，从而提高我们对南极冰块损失导致海平面上升的预测的理解。这个项目将使用基于代理的大气重建和一个高分辨率的海洋模型来生成第一个数据受限的阿蒙森海湾区20世纪海洋状况的后播模拟。该项目将缩小年平均表面温度、海平面气压和表面纬向风异常的尺度，以产生每日分辨的数据集，通过将重新分析的亚年度变化添加到每个重建的状态来模拟真实的海洋状态。这些缩小尺度的古气候重建将使用MITGCM的一个区域区域，其中包括动态海冰和热力冰架表示，为海洋模拟的集合提供强迫。通过四组模拟，首先验证了用缩小尺度的代理重构大气场作为模式强迫的有效性，然后研究了1940年代异常西风事件的原因，最后探讨了20世纪大气趋势对海洋状况的影响。该项目将为研究南极洲西部温室气体浓度上升与冰川消退之间的不同途径提供关键的新见解。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The glaciers in the Amundsen Sea Embayment of West Antarctica, such as Thwaites and Pine Island Glaciers, are rapidly retreating and contributing to sea level rise. There is evidence that the current stage of retreat began in the mid-20th century before the start of the observational record, making it difficult to understand the cause of glacier change. While modeling studies suggest that anthropogenic forcing starting in the early 1900s causing a trend toward stronger westerly conditions and consequently warmer ocean conditions near glaciers, new proxy-based reconstructions of winds since the early 1900s provide robust evidence that wind trends in this region were likely easterly instead of westerly. This project will leverage ocean models to address whether a 20th century easterly wind trend could lead to warmer ocean conditions near glaciers in the Amundsen Sea, improving our understanding of projections of sea level rise due to Antarctic ice mass loss.This project will generate the first data-constrained hindcast simulation of 20th century ocean conditions in the Amundsen Sea Embayment, using proxy-based atmospheric reconstructions and a high-resolution ocean model which has been validated against past observations. The project will downscale annual mean surface temperature, sea level pressure, and surface zonal wind anomalies to produce daily resolved datasets, simulating realistic ocean states by adding sub-annual variability from reanalyses to each of the reconstructed states. These downscaled paleoclimate reconstructions will provide forcing for ensembles of ocean simulations using a regional domain of the MITgcm that includes dynamic sea ice and thermodynamic ice shelf representation. Four sets of simulations are targeted, first to verify the efficacy of using downscaled proxy-reconstructed atmospheric fields as model forcing, then to investigate the causes of the anomalous westerly wind event of the 1940s, and finally to explore the impact of 20th century atmospheric trends on ocean conditions. This project will provide key new insight into the varied pathways that link rising greenhouse gas concentrations to glacier retreat in West Antarctica.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.