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