Kawaguchi Yusuke, Hoppmann Mario, Shirasawa Kunio, Rabe Benjamin, Kuznetsov Ivan
Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwa-no-ha, Chiba, 277-8564, Japan.
Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany.
Sci Rep. 2024 Jul 4;14(1):15446. doi: 10.1038/s41598-024-66124-8.
The ice-ocean drag coefficient and turning angle are crucial parameters in ice-ocean coupled simulations, determining the transfer of momentum between the two media. These parameters are often treated as constants regardless of the static stability at the ice-ocean interface. This study investigates the variability of and based on direct observations of thermal and kinetic energy balance. The observations were conducted beneath multiyear ice packs widely across the central Arctic during a period transitioning from ablation to refreezing, indicating significant variability of = 1-130 10 and = - 19-1° at 5 m depth. Comparing different stations, the observations suggest a pronounced dependence of on the stability parameter ( ) resulting from mechanical and buoyant forcing. rapidly decays with increasing , indicating that the ice-to-ocean momentum transfer is enhanced for neutral or unstable conditions, while it is weakened for stable conditions. In addition, observed vertical profiles of currents revealed that tends to be smaller for unstable and larger for stable conditions. We suggest that numerical simulations using constant values could result in an underestimate of large-scale near-surface currents during the ice growing period.
海冰-海洋拖曳系数和转向角是海冰-海洋耦合模拟中的关键参数，决定了两种介质之间的动量传递。这些参数通常被视为常数，而不考虑海冰-海洋界面处的静力稳定性。本研究基于对热能和动能平衡的直接观测，研究了拖曳系数和转向角的变异性。观测是在北极中部多年冰覆盖区广泛开展的，时间跨度为从消融期到重新冻结期的过渡阶段，结果表明在5米深度处，拖曳系数范围为1 - 130×10⁻³，转向角范围为 - 19 - 1°，存在显著变异性。比较不同站点后，观测结果表明拖曳系数明显依赖于由机械强迫和浮力强迫产生的稳定性参数（ ）。随着 的增加，拖曳系数迅速衰减，这表明在中性或不稳定条件下，海冰到海洋的动量传递增强，而在稳定条件下则减弱。此外，观测到的海流垂直剖面显示，在不稳定条件下拖曳系数往往较小，而在稳定条件下则较大。我们认为，使用常数值进行数值模拟可能会导致低估冰生长期间的大规模近表层海流。
