PUBLISHED WORK
VARIABILITY OF SOUTH PACIFIC TROPICAL WATER SUBDUCTION AND ITS TRANSPORT DOWNSTREAM
Lu, X., R. A. Fine, and T. Qu, 2018, resubmitted to JGR-Oceans.
South Pacific Tropical Water (SPTW) is characterized by a vertical salinity maximum (35.6-36.5 psu) observed at , in the upper thermocline 24.0 to 25.0 kg m-3. SPTW annual subduction rates for two periods are calculated using two methods. Interannual and possibly longer variability are examined. In the first method, monthly Argo data are used from September 2005 to August 2013. Over the entire subtropical SP, there are two subduction maxima, and lateral induction dominates in both. One maximum corresponds to SPTW. Annual subduction rates for SPTW over the Argo period vary from 17 to 35 m yr-1 8.5%, and they positively correlate with Southern Oscillation Index (SOI) and wind stress curl. The SOI was shown previously to affect strength of South Equatorial Current (SEC), which then affects westward extension of high salinity subsurface SPTW. Transport of SEC leads the westward extension of SPTW indicated by salinity being higher than 36.2 psu. SEC transport exhibits a three-year cycle, with each cycle containing an El Niño-Southern Oscillation event. Furthermore, dynamics of SEC variability is affected by Rossby waves, which also affect SPTW westward transport. In the second method over the same SPTW volume, CFC-12 data from the 1990s give an average rate of 35 m yr-1 15%. During the Argo period SPTW lateral induction and subduction rates vary interannually with the SOI. Differences between the two methods and changes in vertical pumping between the two decades are used to explain possibly longer period changes in SPTW subduction rates.
DOWNSTREAM IMPACTS OF ENSO INDUCED TEMPERATURE AND SALINITY ANOMALIES IN SOUTH PACIFIC TROPICAL WATER
Lu, X., R. A. Fine, and T. Qu, 2018, to be submitted to Nature-Climate change.
Developing a new understanding of the variability of temperature and salinity anomalies in South Pacific Tropical Water (SPTW) and their downstream impacts may possibly provide a mechanism for downstream water circulations. The anomalies of SPTW are examined using Argo float data for the period 2005 to 2014. Two temperature/salinity anomalies with respect to climatological mean are found during the studied period over 24 < σθ< 25 kg m-3 isopycnals. The temperature and salinity anomalies within the strongest propagation area are correlated with SOI. Downstream, the potential density anomaly appears to be slightly negative for the warm/salty anomaly and slightly positive for the cold/fresh anomaly, showing temperature anomalies are having a stronger influence on density than the salinity anomalies for SPTW. Surface buoyancy flux shows the ocean surface becomes less buoyant during warm/salty anomaly propagation years and more buoyant during cold/fresh anomaly propagation years, with both changes start from the second year after the appearance of the anomalies. Thus, the downstream vertical exchange of water between surface and subsurface is intensified during warm/salty anomaly years and slowed down during cold/fresh anomaly years. SPTW anomalies appears to affect the downstream water circulation.