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Other transient tracers

The age models produced by trace can be combined with the age history of an arbitrary transient traces to yield estimates of the atmospheric transient invasion of the ocean. So far, only nitrous oxide (N2O) has been implemented. The routine first runs trace and then applies the TTD to a user-specified N2O trajectory.

Experimental

This routine is experimental, and is subject to further validation and peer-review in a manuscript in preparation.

The relevant output quantities are:

  • n2o: Preformed nitrous oxide equilibrium concentration, in nmol kg-1.
  • n2o_ref: Preindustrial preformed nitrous oxide equilibrium concentration, in nmol kg-1.
  • pn2o: Preformed nitrous oxide equilibrium partial pressure, in natm.
  • pn2o_ref: Preindustrial preformed nitrous oxide equilibrium partial pressure, in natm.
  • n2o_prime: Concentration of atmospheric transient nitrous oxide, equal to (n2o-n2o_ref). This is analagous to Canth, except that the imperfectly-transient nature of nitrous oxide precludes denoting this fraction "anthropogenic".
output = trace_n2o(
    output_coordinates=np.array([[0, 0, 0], [0, 0, 0]]),
    dates=np.array([2000, 2010]),
    predictor_measurements=np.array([[35], [35]]),
    predictor_types=np.array([1]),
    atm_co2_trajectory=1
)

>>> output

<xarray.Dataset> Size: 528B
Dimensions:           (loc: 2)
Coordinates:
    year              (loc) <U20 160B '2000-01-01T00:00:00Z' '2010-01-01T00:0...
    lon               (loc) float64 16B 0.0 0.0
    lat               (loc) float64 16B 0.0 0.0
    depth             (loc) float64 16B 0.0 0.0
Dimensions without coordinates: loc
Data variables: (12/20)
    canth             (loc) float64 16B 56.06 66.46
    mean_age          (loc) float64 16B 1.883 1.883
    mode_age          (loc) float64 16B 0.4424 0.4424
    dic               (loc) float64 16B 1.925e+03 1.935e+03
    dic_ref           (loc) float64 16B 1.869e+03 1.869e+03
    pco2              (loc) float64 16B 322.4 337.9
               ...
    scale_factors     (loc) float64 16B 0.01341 0.01341
    n2o               (loc) float64 16B 5.508 5.641
    n2o_ref           (loc) float64 16B 4.753 4.753
    pn2o              (loc) float64 16B 282.6 289.4
    pn2o_ref          (loc) float64 16B 243.9 243.9
    n2o_prime         (loc) float64 16B 0.755 0.8876
Attributes:
    Conventions:        CF-1.10
    description:        Results of Tracer-based Rapid Anthropogenic Carbon Es...
    history:            TRACE version 1.1.0, 2026-09-09 12:01:38.357082 Pytho...
    date_created:       2026-09-09 12:01:38.357096
    references:         doi.org/10.5194/gmd-19-5961-2026
    co2sys_parameters:  CO2System settings.\n├─ EQUILIBRIUM CONSTANTS:\n│  ├─...
    trace_parameters:   per_kg_sw_tf: True, canth_diseq: 1.0, eos: seawater, ...

>>> output.n2o_prime.data

array([0.75498545, 0.88762136])

Arguments

Arguments to trace_n2o are the same as those of trace, with two optional additional parameters:

Additional trace_n2o Arguments

  • atm_n2o_trajectory: Integer between 1 and 9 specifying the atmospheric xN2O trajectory. This history has not been modified to reflect the values that would be expected in the surface ocean given the slow response of the surface ocean to a rapidly changing atmospheric value. Custom columns can be added to data/N2OTrajectories.txt and referenced here.

    • 1. Historical/Linear (default)
    • 2. SSP1_1.9
    • 3. SSP1_2.6
    • 4. SSP2_4.5
    • 5. SSP3_7.0
    • 6. SSP3_7.0_lowNTCF
    • 7. SSP4_3.4
    • 8. SSP4_6.0
    • 9. SSP5_3.4_over

  • preindustrial_xn2o: Optional preindustrial reference xN2O value. The default is 271.