Manucharyan Georgy E, Lopez-Acosta Rosalinda, Wilhelmus Monica M
School of Oceanography, University of Washington, Seattle, Washington, 98195, USA.
Department of Mechanical Engineering, University of California, Riverside, Riverside, California, 92521, USA.
Sci Rep. 2022 Apr 29;12(1):7070. doi: 10.1038/s41598-022-10712-z.
Under-ice eddies are prevalent in the major circulation system in the western Arctic Ocean, the Beaufort Gyre. Theoretical studies hypothesize that the eddy-driven overturning and the ice-ocean drag are crucial mechanisms of the gyre equilibration in response to atmospheric winds. However, due to severe weather conditions and limitations of remote sensing instruments, there are only sparse eddy observations in the ice-covered Arctic Ocean. Hence, the evolution of the under-ice eddy field, its impact on the gyre variability, and their mutual response to the ongoing Arctic warming remain uncertain. Here, we infer the characteristics of the under-ice eddy field by establishing its tight connection to the angular velocities of isolated spinning sea ice floes in marginal ice zones. Using over two decades of satellite observations of marginal ice zones in the western Arctic Ocean, we identified and tracked thousands of floes and used idealized eddy modeling to infer the interannual evolution of the eddy energetics underneath the ice. We find that the eddy field is strongly correlated to the strength of the Beaufort Gyre on interannual timescales, which provides the major observational evidence consistent with the hypothesis of the gyre equilibration by eddies. The inferred trends over the past two decades signify that the gyre and its eddy field have been intensifying as the sea ice cover has been declining. Our results imply that with continuing sea ice decline, the eddy field and the Beaufort Gyre will keep intensifying and leading to enhanced transport of freshwater and biogeochemical tracers.
北冰洋西部主要环流系统波弗特环流中，冰下涡旋普遍存在。理论研究推测，涡旋驱动的翻转和海冰-海洋拖曳力是该环流响应大气风达到平衡的关键机制。然而，由于恶劣的天气条件和遥感仪器的局限性，在冰封的北冰洋中只有稀疏的涡旋观测数据。因此，冰下涡旋场的演变、其对环流变化的影响以及它们对北极持续变暖的相互响应仍不明确。在此，我们通过建立冰下涡旋场与边缘冰区孤立旋转海冰浮冰角速度的紧密联系，推断出冰下涡旋场的特征。利用二十多年来对北冰洋西部边缘冰区的卫星观测数据，我们识别并追踪了数千个浮冰，并使用理想化涡旋模型推断冰下涡旋能量学的年际演变。我们发现，在年际时间尺度上，涡旋场与波弗特环流的强度密切相关，这为涡旋使环流达到平衡这一假设提供了主要观测证据。过去二十年推断出的趋势表明，随着海冰覆盖面积的减少，环流及其涡旋场一直在增强。我们的研究结果表明，随着海冰持续减少，涡旋场和波弗特环流将持续增强，并导致淡水和生物地球化学示踪剂的输送增加。
