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Isopycnal analysis of float 5145 data (part 2)

The float trajectory is shown in Fig. 1. The float has been drifted eastward on average.

../../../../../../_images/float_5145_traj.png

Figure 1: Trajectory of float 5145. Red dots show Jan. 1, 2008 near the start and every half a year later.

The potential density, potential temperature, salinity and nitrate along float 5145 are shown in Figs. 2, 3, 4 and 5, respectively. The contours for three isopycnals (σ = 24.425, 24.5 and 24.575 kg/m^3) are superimposed.

The isopycnal 24.5 kg/m^3 visited by the float undergoes significant interannual variability. It slowly rises (and/or the float is visiting a region where the isopycnal is shallower) until about day 420 (after Jan. 1, 2008) where a winter vertical mixing event occurs. Then, the isopycnal deepens (or the float is visiting a region where the isopycnal is deeper) during the rest of the year until the new recent winter mixing event.

../../../../../../_images/float_5145_sigma_z_t.png

Figure 2: Potential density (kg/m^3) measured by the float 5145. The vertical dashed lines show Jan. 1 of each year. The horizontal dashed line shows the mean depth of the isopycnal σ = 24.5 kg/m^3 over the period. The plain black lines show three isopycnals: σ = 24.425, 24.5 and 24.575 kg/m^3. All figures are made with float_analysis.m in /home/ipu1/userdirs/francois_moli5/RESEARCH/PROJECTS/MARINE_BIOLOGY/SUBMESOSCALE_PROCESSES/FSLE/analysis/Johnson_etal_09.

../../../../../../_images/float_5145_theta_z_t.png

Figure 3: Same as Fig. 1 but for the potential temperature (deg. C).

../../../../../../_images/float_5145_salt_z_t.png

Figure 4: Same as Fig. 1 but for salinity (psu).

../../../../../../_images/float_5145_ntr_z_t.png

Figure 5: Same as Fig. 1 but for nitrate (microM) and the three isopycnals are shown with white plain lines.

../../../../../../_images/float_5145_theta_salt_ntr_24_5_t.png

Figure 6: (a) Potential temperature, (b) salinity and (c) nitrate along σ = 24.5 kg/m^3.

../../../../../../_images/float_5145_theta_salt_52m_t.png

Figure 7: (a) Potential temperature and (b) salinity at 52 m.

../../../../../../_images/float_5145_theta_salt_112m_t.png

Figure 8: (a) Potential temperature and (b) salinity at 112 m.

  • Look at a deeper isopycnal, one that does not outcrop and have larger nitrate values.
  • Remove the signal in all quantities due to the displacement of the float through space and gradients.
  • Do anomalies in nitrate correspond to water from a remote origin and salinity anomalies?
  • Using other ARGO floats and AVISO SSHA, do upwelling/downwelling anomalies occur inside, outside or at the edges of eddies?