Ocean Dynamics Group, New Zealand National Institute of Water and Atmospheric Research, Wellington 6241, New Zealand;
Department of Physics, University of Auckland, Auckland 1010, New Zealand.
Proc Natl Acad Sci U S A. 2020 Jul 21;117(29):16799-16804. doi: 10.1073/pnas.1910760117. Epub 2020 Jun 29.
The stability of large Antarctic ice shelves has important implications for global sea level, sea ice area, and ocean circulation. A significant proportion of ice mass loss from these ice shelves is through ocean-driven melting which is controlled by largely unobserved oceanic thermodynamic and circulatory processes in the cavity beneath the ice shelf. Here we use direct measurements to provide evidence of the changing water column structure in the cavity beneath the Ross Ice Shelf, the planet's largest ice shelf by area. The cavity water column data exhibit both basal and benthic boundary layers, along with evidence of tidally modulated and diffusively convecting internal mixing processes. A region of thermohaline interleaving in the upper-middle water column indicates elevated diffusion and the potential to modify the cavity circulation. The measurements were recorded using the Aotearoa New Zealand Ross Ice Shelf Program hot water drill borehole melted in the central region of the shelf in December 2017 (HWD2), only the second borehole through the central region of the ice shelf, following J9 in 1977. These data, and comparison with the 1977 data, provide valuable insight into ice shelf cavity circulation and aid understanding of the evolution of the presently stable Ross Ice Shelf.
大型南极冰架的稳定性对全球海平面、海冰面积和海洋环流有重要影响。这些冰架的大量冰质量损失是通过海洋驱动的融化造成的，而这种融化受到冰架下腔中大部分未被观测到的海洋热力学和环流过程的控制。在这里，我们使用直接测量来提供罗斯冰架（地球上面积最大的冰架）下方腔体内不断变化的水柱结构的证据。腔体内水柱数据显示了底部边界层和海底边界层，以及潮汐调制和扩散对流内部混合过程的证据。中上水柱中的温盐交错区域表明扩散增强，并有改变腔室环流的潜力。这些测量是使用新西兰奥塔哥罗斯冰架计划于 2017 年 12 月在冰架中心区域钻的热水钻孔（HWD2）记录的，这是继 1977 年 J9 之后第二次穿过冰架中心区域的钻孔。这些数据，以及与 1977 年数据的比较，为冰架腔室环流提供了有价值的见解，并有助于理解目前稳定的罗斯冰架的演变。
