A case study of anomalous horizontal heat transport by an anticyclonic warm eddy in the Canada Basin

The widely active mesoscale processes in the Canada Basin, such as subsurface eddies, have a significant impact on the heat redistribution in the upper ocean and sea ice dynamics. This study utilized MITgcm LLC4320 high-resolution (1/48°) simulation data to track an anticyclonic warm eddy generated by a meandering flow near the southern continental slope of the Canada Basin. The results showed that the heat content of the eddy underwent four stages of evolution before and after entering the sea ice–covered area: transformation in the jet stream region, dissipation after leaving the sea ice, rapid decay at the ice edge, and stabilization under the ice. Within the boundary current, the heat content initially decreased and then increased. During detachment from the current, it decreased from 7.55 × 10 8 J m −2 to 6.93 × 10 8 J m −2 ; after entering the ice-edge zone, surface cooling caused a rapid decline to 5.9 × 10 8 J m −2 . Once fully beneath the sea ice, the heat content stabilized (approximately 5.8 × 10 8 J m −2 ), indicating that the eddy primarily transported heat over long distances through advective processes. During this phase, the efficiency of anomalous heat transport was mainly limited by the reduced translation speed of the eddy under the ice. The aforementioned stages of thermal evolution could represent a characteristic behavior pattern for anticyclonic warm eddies entering the ice-covered regions in this area. These results underscore the crucial role of mesoscale dynamics in controlling heat transport and thermohaline coupling in the Arctic Ocean. 加拿大海盆中广泛存在的中尺度过程(如次表层涡旋)对上层海洋的热量再分配及海冰动力学具有重要影响.本研究利用MITgcm LLC4320高分辨率(1/48°)模拟数据, 追踪了一个由加拿大海盆南部陆坡附近弯曲流场生成的反气旋暖涡.结果表明, 该涡旋在进入海冰覆盖区前后, 其热含量经历了四个演化阶段:急流区的转变阶段,离开海冰后的消散阶段,海冰边缘的快速衰减阶段以及冰下的稳定阶段.在边界流内部, 涡旋热含量先减小后增大;在脱离边界流期间, 热含量从7.55 × 10 8 J m −2 下降至6.93 × 10 8 J m −2 ;进入海冰边缘带后, 表层冷却导致热含量迅速降至5.9 × 10 8 J m −2 .完全进入海冰下方后, 热含量趋于稳定(约5.8 × 10 8 J m −2 ), 表明该涡旋主要通过平流过程实现长距离热量输运.在此阶段, 异常热量输运的效率主要受到冰下涡旋平移速度降低的限制.上述热演化阶段可能代表了该区域反气旋暖涡进入海冰覆盖区的一种典型行为模式.这些结果强调了中尺度动力学在控制北冰洋热量输运及温盐耦合过程中的关键作用.