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, based on the same atmospheric histories and trajectories informing CO₂. The routine first runs trace() and then applies the TTD to the user-specified N₂O trajectory.

This routine is very 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 C_anth, 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])