Estimate temperature- or density-threshold mixed-layer depth

Usage

mixed_layer_depth(
  x,
  method = "temperature_threshold",
  variable = NULL,
  reference_depth_m = 10,
  threshold = 0.2,
  support = c("local", "all")
)

Arguments

x: A direct source-profile <ocean_cube> for the C8 temperature method, or a certified C9 thermodynamic-state cube for the C10 density method.
method: "temperature_threshold" or "density_threshold".
variable: Optional exact eligible temperature variable, or exactly sea_water_potential_density for the density method.
reference_depth_m: Finite non-negative reference depth in canonical physical metres, positive downward.
threshold: Finite positive departure threshold. If omitted, the method-specific defaults are 0.2 K/degree Celsius for temperature and 0.03 kg m-3 for potential density.
support: Vertical connectivity policy. "local" stops at the first explicit support gap; "all" may inspect beyond it but never localizes an exact MLD through a gapped path.

Value

A base data.frame with one row per longitude, latitude, and time. Resolved rows contain the first physical threshold crossing below the reference depth. Unresolved rows retain the governing reference, gap, missingness, or open-bottom status.

Details

C8 implements only a point-profile temperature threshold. The reference temperature is observed exactly or linearly interpolated from a locally adjacent supported pair. The first deeper point whose absolute departure from that reference is at least threshold is selected; a locally supported bracket may be linearly interpolated in departure magnitude. Missing values and explicit gaps are never bridged, and no crossing before the observed bottom is reported as open rather than replaced by the deepest level.

The C10 density method consumes only C9 potential density referenced to exactly 0 dbar and uses the first positive departure from the 10 m reference; it never uses absolute density departure or recomputes TEOS-10 state.

References

de Boyer Montegut, C. et al. (2004). Mixed layer depth over the global ocean: An examination of profile data and a profile-based climatology. Journal of Geophysical Research: Oceans, 109, C12003. doi:10.1029/2004JC002378

Examples

if (FALSE) { # \dontrun{
mixed_layer_depth(cube)
mixed_layer_depth(cube, reference_depth_m = 10, threshold = 0.2)
} # }