Observations of Modified Warm Deep Water Beneath Ronne Ice Shelf, Antarctica, From an Autonomous Underwater Vehicle
Observations of Modified Warm Deep Water Beneath Ronne Ice Shelf, Antarctica, From an Autonomous Underwater Vehicle
复制标题
通过自主水下航行器对南极洲罗纳冰架下改良的温暖深水进行观测
作者：
Davis P
菲尔希纳-龙冰架 (FRIS) 是世界上体积最大的冰架。它有助于调节南极洲对全球海平面上升的贡献，以及冰架下空腔内的水团转变产生全球重要的致密水团。然而，冰架基底融化率相对较低，因为威德尔海大陆架上产生寒冷（-1.9°C）且稠密的高盐度陆架水，将冰架与大规模流入的温水隔离开来。尽管如此，观察到一股相对温暖（−1.4°C）的改良暖深水（MWDW）流入伯克纳浅滩的西侧，到达罗纳冰锋，尽管控制其循环和命运的过程仍然不确定。在这里，我们展示了使用 Autosub 远程自主水下航行器在冰架腔内沿温水流入进行的首次观测。我们观察到 MWDW 的核心向西南方向的速度为 4 cm s−1，到达冰下腔至少 18 公里。水文特性在空间上是异质的，导致由潮汐平流驱动的时间变化。最高的湍流耗散率与最热的 MWDW 相关，垂直涡流扩散率达到 10−4m2s−1，此时水柱完全湍流。混合效率接近标准值0.2。模型研究表明，在不断变化的气候中，MWDW 可能成为 FRIS 下方的主要水团，这为更全面地了解 MWDW 流入的动态提供了强大的动力。
Filchner‐Ronne Ice Shelf (FRIS) is the world's largest ice shelf by volume. It helps regulate Antarctica's contribution to global sea level rise, and water mass transformations within the sub‐ice‐shelf cavity produce globally important dense water masses. Rates of ice shelf basal melting are relatively low, however, as the production of cold (−1.9°C) and dense High Salinity Shelf Water over the Weddell Sea continental shelf isolates the ice shelf from large‐scale inflow of warm water. Nevertheless, a narrow inflow of relatively warm (−1.4°C) Modified Warm Deep Water (MWDW) that hugs the western flank of Berkner Bank is observed to reach Ronne Ice Front, although the processes governing its circulation and fate remain uncertain. Here we present the first observations taken within the ice shelf cavity along this warm water inflow using the Autosub Long Range autonomous underwater vehicle. We observe a core of MWDW with a south‐westward velocity of 4 cm s−1that reaches at least 18 km into the sub‐ice cavity. The hydrographic properties are spatially heterogeneous, giving rise to temporal variability that is driven by tidal advection. The highest rates of turbulent dissipation are associated with the warmest MWDW, with the vertical eddy diffusivity reaching 10−4m2s−1where the water column is fully turbulent. Mixing efficiency is close to the canonical value of 0.2. Modeling studies suggest MWDW may become the dominant water mass beneath FRIS in our changing climate, providing strong motivation to understand more fully the dynamics of this MWDW inflow.