DOI: 10.5281/zenodo.12773589
title: Data for 'Local verses farfield control on South Pacific mode water variability'

description: The adjoint files contained in two .zip folders here are the output files of two adjoint sensitivity experiments in the South Pacific mode water formation regions, CENTRAL and EASTERN, using ECCOv4r4. The first set of outputs is for the sensitivity of the volume in the Central mode water pool to net heat flux. The folder CENTRAL.zip contains these files which are of the form ADJqnet_CENTRAL.XX.data/.meta, where XX is the timestep. The second set of outputs is for the sensitivity of the volume in the Eastern mode water pool to net heat flux. The folder EASTERN.zip contains these files which are of the form ADJqnet_EASTERN.XX.data/.meta, where XX is the timestep. Both sets of data contained here are the output/sensitivity files for 6 years at 14 day time steps.

The forward perturbation files contained in four .zip folders here are the output files of four separate forward perturbation experiments, using ECCOv4r4. The first set of outputs is for a forward perturbation experiment related to the Central mode water pool sensitivities, where the perturbation is set in an area of negative sensitivity and uses a negative perturbation in the folder C_ns_np.zip. The folder C_ns_np.zip contains these files which are of the form THETA_mon_mean.XX.data/.meta, SALT_mon_mean.XX.data/.meta, and MXLDEPTH_mon_mean.XX.data/.meta, where XX is the times. The second set of outputs is for a forward perturbation experiment related to the Central mode water pool sensitivities, where the perturbation is set in an area of negative sensitivity and uses a positive perturbation in the folder C_ns_pp.zip. The folder C_ns_pp.zip contains these files which are of the form THETA_mon_mean.XX.data/.meta, SALT_mon_mean.XX.data/.meta, and MXLDEPTH_mon_mean.XX.data/.meta, where XX is the times. The third set of outputs is for a forward perturbation experiment related to the Central mode water pool sensitivities, where the perturbation is set in an area of positive sensitivity and uses a negative perturbation in the folder C_ps_np.zip. The folder C_ps_np.zip contains these files which are of the form THETA_mon_mean.XX.data/.meta, SALT_mon_mean.XX.data/.meta, and MXLDEPTH_mon_mean.XX.data/.meta, where XX is the times. The fourth set of outputs is for a forward perturbation experiment related to the Central mode water pool sensitivities, where the perturbation is set in an area of positive sensitivity and uses a positive perturbation in the folder C_ps_pp.zip. The folder C_ps_pp.zip contains these files which are of the form THETA_mon_mean.XX.data/.meta, SALT_mon_mean.XX.data/.meta, and MXLDEPTH_mon_mean.XX.data/.meta, where XX is the times. All sets of data contained here are the output/forward perturbation files for 3 years at 14 day time steps, starting when the perturbation begins. The THETA and SALT files from the forward perturbation experiments are used to create neutral density files using the gibbs seawater toolbox in MATLAB. These perturbed neutral densities are then used to find the difference the perturbation makes in relation to a control experiment.

 Paper abstract: In the South Pacific mode water formation region, central and eastern pools of mode water have been found to be linked to winter mixed-layer thicknesses that vary strongly interannually and out of phase across the basin. This mixed-layer variability is associated with peaks in sea level pressure variability at a quasi-stationary anomaly situated between the two pools. To investigate how surface forcing, as well as the propagation of upstream anomalies, affects the formation of these mode water pools, a set of adjoint sensitivity experiments with a density-following feature are conducted. Adjoint sensitivities reveal local cooling can lead to an increase in mode water pool volume through mixed-layer depth changes and lateral density surface movement. In addition, upstream warming along the Antarctic Circumpolar Current can lead to an increase in mode water pool volume through lateral density surface movement. Optimal conditions for mode water formation involve a combination of local cooling and upstream warming of mode water formation sites. Hence, South Pacific mode water variability is particularly sensitive to atmospheric modes which lead to a dipole in heating across the formation sites.