PUBLIC APPEARANCES
2014 AGU FALL MEETING
San Francisco, CA, December 2014
Presented a poster "Variability of South Pacific Tropical Water Subduction".
South Pacific Tropical Water (SPTW) is characterized by a vertical salinity maximum 35.6-36.5 psu located at 8°S-25°S, 160°W-110°W and lying in the upper thermocline between 24.0 and 25.0 σθ. Annual subduction rates for SPTW for two different periods are calculated using two methods. In the first method, monthly 1°×1° Argo data are used to calculate subduction rates from September 2005 to August 2013, also lateral induction and vertical pumping are calculated. Over the entire South Pacific, there are two subduction maxima, and the lateral induction process dominates in both maxima. One of the maxima corresponds to SPTW. For the SPTW, annual subduction rates from Argo data vary from 15 to 26 m/yr ±7.5% during the 8 year period. SPTW subduction rates are shown to be positively correlated with Southern Oscillation Index (SOI) and wind stress curl. The SOI was shown before to affect variability of South Equatorial Current (SEC). Transport of SEC may lead the westward extension of subsurface SPTW areas where salinity is higher than 36.2 psu. The subsurface SPTW areas have a three-year cycle, with each cycle containing an ENSO event. In the second method and over the same SPTW volume, CFC-12 data from the 1990s World Ocean Circulation Experiment are used to calculate an average subduction rate of 35±15% m/yr. SPTW subduction rates have been shown to vary interannually and possible decadally.
2016 OCEAN SCIENCES MEETING
New Orleans, LA, February 2016
Given an oral presentation "Variability of Salinity and Temperature Anomalies in South Pacific Tropical Water".
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 ENSO modulations. The anomalies of SPTW are examined using Argo data. We use quality controlled 1°×1° gridded monthly data for the period 2005 to 2014 from Asian-Pacific Data Research Center of the IPRC, trying to investigate density-compensated spiciness anomalies. Annual mean salinity anomalies, temperature anomalies and potential density anomalies averaged over 24 < σθ< 25 kg m-3 isopycnals are plotted, where the anomalies are deviations from the mean field of 2005 to 2014 monthly climatology and each depth at each gridded point has its own mean. Two salinity/temperature anomalies are found during the studied period. A warm/salty anomaly appears in the region of 130°W-110°W at about 15°S in 2005, propagates to the west and ends in 2009. In 2011 a cool/fresh anomaly is found at the subduction region of SPTW at about 18°S and 120°W, which migrates northwestward to 170°W-150°W and 10°S in 2014. 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. We are investigating the possible connections that these salinity/temperature anomalies could have to Rossby waves and atmospheric forcing.
2018 OCEAN SCIENCES MEETING
Portland, OR, February 2018
Presented a poster "Non-Density Compensated Temperature and Salinity Anomalies in the Tropical/Subtropical South Pacific and Their Downstream Impacts"
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Climate change has been increasing temperature (T) and salinity (S) of tropical/subtropical ocean. T/S anomalies are tested for density compensation using Argo data (2005 to 2014) and CCSM4 and tracked for potential impacts on circulation. Using Argo data, we observe two pairs of non-density compensated T/S anomalies (with respect to the Argo period mean). The anomalies originate at about 20°S, 120°W and are observed in South Pacific Tropical Water at 24 - 25 kg m-3 isopycnals. Warm/salty anomalies are produced during El Niño phase, and cold/fresh anomalies are produced during La Niña phase. Downstream vertical exchange of water between the surface and subsurface is intensified during warm/salty anomaly years and weakened during cold/fresh anomaly years. Thus, both anomalies appear to affect the downstream vertical exchange in the tropics. Using 20-year output form CCSM4, similar non-density compensated T/S anomaly propagation has been identified. As in the data, model T/S anomalies propagate westward with the South Equatorial Current, and after reaching the western boundary some continue equatorward – taking about two years. Subsurface warm/salty anomalies mix upward into the surface layer. There is increased evaporation over the western Pacific warm pool two years after warm/salty anomalies reach the western boundary. Thus, warm/salty anomalies appear to affect equatorial surface characteristics, and by doing so have the potential to affect the atmosphere.