Deep ocean circulation in the subpolar North Atlantic observed by acoustically-tracked floats
Deep ocean circulation in the subpolar North Atlantic observed by acoustically-tracked floats
复制标题
通过声学跟踪浮标观测北大西洋副极地深海环流
DOI：
10.1016/j.pocean.2023.102975
复制
发表时间：
2023
影响因子：
4.1
通讯作者：
Furey, Heather H.
中科院分区：
文献类型：
--
作者：
Zou, Sijia;Bower, Amy S.;Lozier, M. Susan;Furey, Heather H.
亚极地北大西洋的深部环流决定了高纬度气候信号向低纬度的传播和混合。然而，由于观测资料的相对稀少，我们目前对亚极地深层环流的了解一直是有限的。为了更好地理解这一点，我们利用从2014年6月至2019年1月期间漂流的122个次表层声学跟踪浮标的直接速度测量，构建了北大西洋深部(1800-2800 dbar)平均速度和涡动动能(EKE)的网格场。平均速度场显示格陵兰岛周围和拉布拉多海存在较强的深边界流，雷克雅内斯海脊东侧的深边界流较弱，西翼的平均流接近于零，表明亚极地盆地存在不连续的深边界流。深EKE虽然震级较小，但总体上类似于海洋表面的EKE模式，包括沿北大西洋洋流路径和形成伊明格环的格陵兰以西的相对较高的EKE模式。关于深EKE的一个令人惊讶的发现是，格陵兰岛以东有一个与海岸平行的隆起带，它不存在于表层EKE区域。这一高EKE带可能是由于丹麦海峡溢流气旋传播、格陵兰东南部近海风生再环流的变异性和/或地形波浪的综合影响所致。本研究中建立的基于浮子的流场提供了一个前所未有的关于北大西洋次极地大尺度深部环流运动学特征的定量视图。结合跨流域欧拉测量，我们认为这些最近的观测为测试和改进深海环流和子午线翻转环流的数值模拟提供了基准，而这两个环流是气候变化预测迫切需要的。
The deep circulation in the subpolar North Atlantic determines the spread and mixing of high latitude climate signals to lower latitudes. However, our current understanding of the subpolar deep circulation has been limited due to relatively sparse observational data. To improve that understanding, we construct gridded fields of mean velocity and eddy kinetic energy (EKE) in the deep (1800–2800 dbar) subpolar North Atlantic using direct velocity measurements from 122 subsurface acoustically-tracked floats that drifted during June 2014–January 2019. The mean velocity field reveals a relatively strong deep boundary current around Greenland and in the Labrador Sea, with a weaker deep boundary current over the eastern flank of the Reykjanes Ridge, and near-zero mean flow over the western flank, implying a discontinuous deep boundary current across the subpolar basin. The deep EKE, albeit with smaller magnitudes, generally resembles the EKE pattern at the ocean surface, including relatively high values along pathways of the North Atlantic Current and west of Greenland where the Irminger Rings are formed. A surprising finding about deep EKE is an elevated band east of Greenland that parallels the coast and is not present in the surface EKE field. This high EKE band is possibly attributed to the combined influence from propagating Denmark Strait Overflow Cyclones, variability of the wind-driven recirculation offshore of southeast Greenland, and/or topographic waves. The float-based flow fields constructed in this study provide an unprecedented quantitative view of the kinematic properties of the large-scale deep circulation in the subpolar North Atlantic. Combined with cross-basin Eulerian measurements, we believe these recent observations provide a benchmark for testing and improving numerical simulations of deep ocean circulation and the Meridional Overturning Circulation, which are urgently needed for climate change predictions.