Lagrangian perspective on the drivers of future AMOC decline: reduced upper limb water availability and weaker diapycnal transformation efficiency

This repository contains data sets supporting the study titled Lagrangian perspective on the drivers of future AMOC decline: reduced upper limb water availability and weaker diapycnal transformation efficiency. The study is based on Lagrangian trajectories evaluated using monthly mean velocity and tracer fileds output from the HadGEM3-GC3.1-HM climate model hist-1950 and highres-future runs. Numerical water parcels are initialised to sample the full-depth southward transport across the 49N latitude section in the Atlantic Ocean every month in 1972 and 1972. Water parcels are advected backwards-in-time using TRACMASS v7.1 Lagrangian particle tracking tool within the subpolar North Atlantic until any one of following termination conditions are met: water parcels reach the Hudson Strait, the Davis Strait, the Fram Strait, or the Barents Sea; water parcels return to the 49N section; water parcels reach the ocean surface; or water parcel reach the maximum advection time of 20-years. The number of water parcels initialised in each model-grid cell scales with the total southward transport through that cell, such that the maximum possible transport conveyed by any single particle is 5 mSv (mSv == 10-3 Sv), resulting in more arount 510 000 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: TRACMASS_MresMIP.zip: the TRACMASS Lagragian particle tracking tool which was used to perform our two experiments in 1972 (a2 namelist) and 2050 (a1 namelist). 2050_experiment_data.tar.gz:The original trajectories data of the 2050 experiment in both csv and parquet format as well as the processed data used in the study. 1972_expt_data.tar.gz: same as 2050_experiment_data.tar.gz but for the 1972 experiment. All Lagrangian experiments were completed and analysed using the JASMIN High-Performance Computing facility (https://jasmin.ac.uk).