Small negative salinities near river outflow

[nichannah]

The min S can go negative near, e.g. Rio de Plata, occasionally. This doesn't look like numerical instability and doesn't go away with a lower timestep.

The minimum S is 4.746731046187E-02 psu at (i,j,k) = ( 897, 347, 1), (lon,lat,dpt) = ( -55.8750, -35.3843, 5.0335 m) The minimum S is -9.460506569319E-02 psu at (i,j,k) = ( 897, 347, 3), (lon,lat,dpt) = ( -55.8750, -35.3843, 25.2194 m) The minimum S is -2.842612159931E-01 psu at (i,j,k) = ( 897, 347, 1), (lon,lat,dpt) = ( -55.8750, -35.3843, 5.0335 m) The minimum S is -4.255482755701E-01 psu at (i,j,k) = ( 897, 347, 1), (lon,lat,dpt) = ( -55.8750, -35.3843, 5.0335 m) The minimum S is -3.992160389502E-01 psu at (i,j,k) = ( 897, 347, 2), (lon,lat,dpt) = ( -55.8750, -35.3843, 15.1006 m) The minimum S is -3.261900299750E-01 psu at (i,j,k) = ( 897, 347, 3), (lon,lat,dpt) = ( -55.8750, -35.3843, 25.2194 m) The minimum S is -2.954316267829E-01 psu at (i,j,k) = ( 897, 347, 4), (lon,lat,dpt) = ( -55.8750, -35.3843, 35.3585 m) The minimum S is -2.671503405474E-01 psu at (i,j,k) = ( 897, 347, 3), (lon,lat,dpt) = ( -55.8750, -35.3843, 25.2194 m) The minimum S is -1.675075110457E-01 psu at (i,j,k) = ( 897, 347, 4), (lon,lat,dpt) = ( -55.8750, -35.3843, 35.3585 m) The minimum S is 3.083211961732E-02 psu at (i,j,k) = ( 897, 347, 4), (lon,lat,dpt) = ( -55.8750, -35.3843, 35.3585 m) The minimum S is 3.156939970899E-01 psu at (i,j,k) = ( 897, 347, 4), (lon,lat,dpt) = ( -55.8750, -35.3843, 35.3585 m) The minimum S is 7.476128076027E-01 psu at (i,j,k) = ( 897, 347, 4), (lon,lat,dpt) = ( -55.8750, -35.3843, 35.3585 m)