Argo Observations A Powerful Tool for Tracking Ocean

Argo Observations: A Powerful Tool for Tracking Ocean Climate Signals Y. N. Sasaki, N. Schneider, N. Maximenko, and K. Lebedev (GRL, 2010) Pacific decadal variability is hypothesized to stem from ocean signals that sink at mid-latitude and travel to the equator. One possible such signal is spiciness (density compensation). The unprecedented temporal and spatial coverage of Argo observations now allows observation of the propagation of spiciness anomalies all the way from the eastern subtropics to the western tropics. Annual mean salinity anomalies averaged over 25< <25. 5 kg/m 3 isopycnals. Contours denote 1. 6 and 3. 4 m 2/s 2 mean Montgomery potential isopleths. Circles denote tracer positions calculated from the mean velocity fields. The top panels show a cool-fresh anomaly appearing in the eastern subtropics at 120 W– 150 W in 2003– 2004. It migrates to the southwest and arrives in the western tropics in 2008. Two warm-salty anomalies travel along the same path from 2003 to 2005, and after 2005. The bottom panel shows the path of the cool-fresh anomaly (blue contours; color denotes long-term mean salinity). The speeds of the spiciness anomalies match the advection speed by the mean geostrophic current. Their amplitudes decrease with time, probably because the temporal variability in the velocity fields diffuses the signals.