Backward particle trajectories used to estimate the catchment area of sediment traps HG-IV and HG-N deployed in Fram Strait@en

To determine the catchment area of sediment traps deployed in Fram Strait, we used a Lagrangian particle tracking algorithm and computed backward particle trajectories. This was done by reversing the flow field, i.e. particles were treated as if they were rising from the mooring location to the surface with a negative settling velocity, being horizontally displaced with the reversed horizontal velocity (vertical ocean velocities were neglected). Particles were advected with daily averaged horizontal model velocities from the ocean-sea ice model FESOM and a constant settling velocity of either 120 m/day, 60 m/day or 20 m/day. They were released at either 200 m or 2300 m depth, and tracked until they reached the surface. The computation of backward particle trajectories was performed for two locations of moorings equipped with sediment traps in central Fram Strait, HG-N and HG-IV. Particles were released once per day during the time period 2002 to 2009, resulting in 2920 trajectories. Considering the 12 experiments (two mooring positions, two depths of release, three settling velocities), altogether 35040 trajectories were calculated. A time step of 1 hour was used for the trajectory calculation, and thus hourly positions and corresponding temperature and salinity values were stored.