Controls on Dense Water Formation along the path of the North Atlantic Subpolar Gyre - Water Parcel Crossings of the OSNAP Array

This dataset contains the initial and final positions and properties of Lagrangian trajectories evaluated using monthly mean velocity and tracer fields output from the ORCA0083-GO8p7 ocean sea-ice model hindcast (1958-2021). Numerical water parcels are initialised to sample the full-depth northward transport across a sub-section of the Overturning in the Subpolar North Atlantic Program (OSNAP) East array (between Reykjanes Ridge and the Scottish Shelf) every month between 1975-2012. Water parcels are advected forwards-in-time using a bespoke version of TRACMASS v7.1 Lagrangian particle tracking tool which enables users to specify a custom domain using a mask netCDF file & output separate _run.csv output files for each trajectory release.

Particles are initialised for 456 consecutive months between 1975 and 2012 before being advected forwards-in-time within the subpolar North Atlantic until any one of four termination conditions are met: (1) water parcels reach the Greenland-Scotland Ridge array, (2) water parcels reach a sub-section of the OSNAP West array at 53N (extending from the Labrador coast to centre of the basin interior), (3) water parcels reach the southern boundary of the experiment domain at 50N, or (4) particles reach the maximum advection time of 9-years.

The number of water parcels initialised in each model-grid cell scales with the total northward transport through that cell, such that the maximum possible transport conveyed by any single particle is 2.5 mSv (mSv == 10-3 Sv), resulting in more than 12.5 million water parcel trajectories.

Water parcel locations (converted to geographical coordinates) and properties (conservative temperature, absolute salinity, potential density [TEOS-10]) are output on every model-grid cell crossing. TRACMASS determines particle properties on grid-cell crossings by taking the average of the properties stored at the nearest two T-grid points.

Here, we provide two .parquet files containing the locations and properties of water parcels on their:

(a) Inital northward crossing of the OSNAP East array (Reykjanes Ridge to Scottish Shelf) and final southward crossings of the OSNAP West array (Labrador coast to basin interior) [ORCA0083-GO8p7_NAC_53N_FinT_1975_2014_crossings.parquet]

(b) Inital northward crossing of the OSNAP East array (Reykjanes Ridge to Scottish Shelf) and intermediate northward crossings of the OSNAP West array (basin interior to West Greenland coast) [ORCA0083-GO8p7_NAC_WGC_FinT_1975_2014_crossings.parquet]

All Lagrangian experiments were completed using the JASMIN High-Performance Computing facility (https://jasmin.ac.uk).

For a complete description of the ORCA0083-GO8p7 hindcast configuration see: Megann et al. (2022).

For a complete description of TRACMASS v7.1 see:  https://www.tracmass.org

To access the version of TRACMASS used in this work see: https://github.com/oj-tooth/Tracmass_v7.1

本数据集包含利用ORCA0083-GO8p7海洋海冰模式后报（1958-2021年）输出的月平均流速场与示踪剂场，计算得到的拉格朗日轨迹（Lagrangian trajectories）初始与终态位置及属性信息。

1975至2012年间，每月均会初始化数值水团，以采样跨副极地北大西洋翻转环流计划（Overturning in the Subpolar North Atlantic Program，简称OSNAP）东阵列（雷克雅内斯海岭与苏格兰陆架之间子区域）的全深度北向输运。数值水团将通过定制版TRACMASS v7.1拉格朗日粒子追踪工具进行时间正向平流输送，该工具支持用户通过掩码NetCDF文件自定义计算域，并为每条轨迹释放生成独立的_run.csv输出文件。

研究于1975至2012年间连续456个月初始化粒子，随后在副极地北大西洋区域内进行时间正向平流输送，直至满足以下四项终止条件之一：(1) 水团抵达格陵兰-苏格兰海岭阵列；(2) 水团抵达OSNAP西阵列位于53°N的子区域（从拉布拉多海岸延伸至海盆内部中心）；(3) 水团抵达实验区域南边界50°N；(4) 粒子平流时长达到最大值9年。

每个模式网格单元中初始化的水团数量，与通过该单元的总北向输运量成正比，因此单个粒子所能输送的最大输运量为2.5毫斯维（mSv，即10⁻³ 斯维（Sv）），最终生成超过1250万条水团轨迹。

水团位置（转换为地理坐标）与属性（保守温度、绝对盐度、位势密度[TEOS-10]）会在每次跨越模式网格单元时输出。TRACMASS通过对最近两个T网格点存储的属性取平均值，来确定粒子跨越网格单元时的属性值。

本数据集提供两个Parquet格式文件，包含水团在以下场景下的位置与属性信息：
(a) 首次北向跨越OSNAP东阵列（雷克雅内斯海岭至苏格兰陆架），以及最终南向跨越OSNAP西阵列（拉布拉多海岸至海盆内部）[文件名为ORCA0083-GO8p7_NAC_53N_FinT_1975_2014_crossings.parquet]
(b) 首次北向跨越OSNAP东阵列（雷克雅内斯海岭至苏格兰陆架），以及中途北向跨越OSNAP西阵列（海盆内部至西格陵兰海岸）[文件名为ORCA0083-GO8p7_NAC_WGC_FinT_1975_2014_crossings.parquet]

所有拉格朗日实验均通过JASMIN高性能计算设施完成（https://jasmin.ac.uk）。

关于ORCA0083-GO8p7后报配置的完整说明，请参见Megann等（2022）的研究。

关于TRACMASS v7.1的完整说明，请参见：https://www.tracmass.org

本研究使用的TRACMASS版本获取地址：https://github.com/oj-tooth/Tracmass_v7.1