Ashkenazy Yosef, Tziperman Eli
Department of Solar Energy and Environmental Physics, The Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, Negev, 84990, Israel.
Department of Earth and Planetary Sciences and School of Engineering and Applied Sciences, Harvard University, 20 Oxford Street, Cambridge, MA, 02138, USA.
Nat Commun. 2021 Nov 4;12(1):6376. doi: 10.1038/s41467-021-26710-0.
The deep (~100 km) ocean of Europa, Jupiter's moon, covered by a thick icy shell, is one of the most probable places in the solar system to find extraterrestrial life. Yet, its ocean dynamics and its interaction with the ice cover have received little attention. Previous studies suggested that Europa's ocean is turbulent using a global model and taking into account non-hydrostatic effects and the full Coriolis force. Here we add critical elements, including consistent top and bottom heating boundary conditions and the effects of icy shell melting and freezing on ocean salinity. We find weak stratification that is dominated by salinity variations. The ocean exhibits strong transient convection, eddies, and zonal jets. Transient motions organize in Taylor columns parallel to Europa's axis of rotation, are static inside of the tangent cylinder and propagate equatorward outside the cylinder. The meridional oceanic heat transport is intense enough to result in a nearly uniform ice thickness, that is expected to be observable in future missions.
木卫二是木星的卫星，其深度约100千米的海洋被一层厚厚的冰壳覆盖，是太阳系中最有可能发现外星生命的地方之一。然而，其海洋动力学及其与冰盖的相互作用却很少受到关注。先前的研究使用全球模型并考虑了非静水效应和完整的科里奥利力，表明木卫二的海洋是湍流的。在这里，我们添加了关键要素，包括一致的顶部和底部加热边界条件以及冰壳融化和冻结对海洋盐度的影响。我们发现微弱的分层主要由盐度变化主导。海洋表现出强烈的瞬态对流、涡旋和纬向急流。瞬态运动在平行于木卫二自转轴的泰勒柱中组织起来，在切圆柱内部是静止的，在圆柱外部向赤道方向传播。经向海洋热传输强烈到足以导致冰厚度几乎均匀，这有望在未来的任务中被观测到。
