3-D Ocean Particle Tracking Modeling Reveals Extensive Vertical Movement and Downstream Interdependence of Closed Areas in the Northwest Atlantic

Novel 3-D passive particle tracking experiments were performed using the Lagrangian particle simulator ‘Parcels’ v 2.1 available at http://www.oceanparcels.org in the northwest Atlantic to elucidate connectivity among areas closed to protect vulnerable marine ecosystems (Wang et al., 2020). Climatological monthly–mean currents were obtained from the Bedford Institute of Oceanography North Atlantic Model (BNAM) ocean model over the period 1990-2015 (Wang et al. 2019). BNAM is an eddy resolving North Atlantic Ocean model with a nominal resolution of 1/12° (approximately ~8 km at the Equator). It is based on NEMO 2.3 (Nucleus for European Modelling of the Ocean) and has a maximum of 50 levels in the vertical, with level thickness increasing from 1 m at the surface to 200 m at a depth of 1,250 m and reaching the maximum thickness of 460 m at the bottom of the deep basins (approximately 5,730 m). BNAM uses partial cell for the bottom layer, which improves the representation of the bottom layer. We provide the monthly-mean U (zonal) V (meridional) and W (vertical) velocities for all 12 months and yearly-averaged current over these months from BNAM in nc format. Also, one mask nc file is given in this area, which includes grid coordinates and indicates the sea (value=1) and land (value=0) of the fields. Using Parcels and BNAM data we examined 1) the degree of vertical movement of particles released at different depths and locations; 2) the location of potential source populations for the deep-sea taxa protected by the closures; and 3) the degree of functional connectivity. We found enhanced connectivity over previously developed 2-D models and unexpected, current-driven, strong (to a maximum of about 1340 m) downward displacement at depth (particles released at 450, 1000 and 2250 m), with weaker upward displacement except for the release depth of 2250 m which showed upward movement of 955 m with a drift duration of 3 months. We provide the distributions of horizontal velocity vectors (cm/s) and vertical velocity contours (m/s x 10-4) at a) 100 m and b) 1,000 m depth in the Flemish Cap area of the northwest Atlantic. These data can be interpolated to reconstruct Figure 8 in our publication and could potentially be used to evaluate benthic pelagic coupling in the region, and be used in species distribution models. Wang, Z., Brickman, D., & Greenan, B.J.W. Characteristic evolution of the Atlantic Meridional Overturning Circulation from 1990 to 2015: An eddy-resolving ocean model study. Deep Sea Res. I. 149, 103056 (2019). https://doi.org/10.1016/j.dsr.2019.06.002.

本研究于西北大西洋海域，依托可从http://www.oceanparcels.org获取的拉格朗日粒子模拟器（Lagrangian particle simulator）‘Parcels’v2.1，开展了新型三维被动粒子追踪实验，以阐明为保护脆弱海洋生态系统而设立的封闭区域之间的连通性（Wang等，2020）。
本研究使用的气候态月平均流场数据，源自贝德福德海洋研究所北大西洋模式（Bedford Institute of Oceanography North Atlantic Model, BNAM），时间跨度为1990年至2015年（Wang等，2019）。BNAM是一款可解析中尺度涡的北大西洋海洋模式，名义分辨率为1/12°（赤道附近约8 km）。该模式基于NEMO 2.3（欧洲海洋建模核心系统，Nucleus for European Modelling of the Ocean）构建，垂直方向最多设置50层，层厚从表层的1 m随深度递增：在1250 m深度处层厚达200 m，在深海盆底部（约5730 m）达到最大层厚460 m。BNAM在底层采用部分网格单元（partial cell）技术，优化了底层海洋环境的模拟效果。
本数据集提供了BNAM模式输出的12个月份的月平均纬向（U）、经向（V）及垂向（W）流速场，以及上述月份的年平均流场，数据格式为nc（netCDF）格式。此外，本数据集附带该研究区域的掩膜nc文件，其中包含网格坐标信息，并通过数值标记区分海域（取值为1）与陆域（取值为0）。
依托Parcels模拟器与BNAM模式数据，本研究开展了三项分析：1）不同深度、不同位置释放的粒子的垂向运动幅度；2）受封闭保护的深海类群的潜在种群源地位置；3）功能连通性程度。研究结果显示，相较于此前已有的二维模型，本研究得到的连通性更强；同时观测到意外的、由海流驱动的强烈垂向位移：在450 m、1000 m及2250 m深度释放的粒子最大向下位移可达约1340 m；仅在2250 m释放深度观测到较弱的向上位移，其3个月的漂移期间内向上移动了955 m。
本数据集还提供了西北大西洋弗拉芒浅滩（Flemish Cap）区域100 m与1000 m深度处的水平流速矢量场（单位：cm/s）与垂向流速等值线（单位：m/s × 10^-4）分布数据。上述数据可通过插值还原本研究论文中的图8，亦可用于评估该区域的底栖-浮游耦合过程，或应用于物种分布模型。
参考文献：Wang, Z., Brickman, D. 与Greenan, B.J.W.，《1990-2015年北大西洋经向翻转环流的特征演变：一项中尺度涡解析海洋模式研究》，《深海研究I辑》，149卷，103056（2019），https://doi.org/10.1016/j.dsr.2019.06.002。