Vertical Structure Anomalies of Oceanic Eddies and Eddy-Induced Transports in the South China Sea

Using satellite altimetry sea surface height anomalies (SSHA) and Argo profiles, we investigated eddy’s statistical characteristics, 3-D structures, eddy-induced physical parameter changes, and heat/freshwater transports in the South China Sea (SCS). In total, 31,744 cyclonic eddies (CEs, snapshot) and 29,324 anticyclonic eddies (AEs) were detected in the SCS between 1 January 2005 and 31 December 2016. The composite analysis has uncovered that changes in physical parameters modulated by eddies are mainly confined to the upper 400 m. The maximum change of temperature (T), salinity (S) and potential density (σθ) within the composite CE reaches −1.5 °C at about 70 m, 0.1 psu at about 50 m, and 0.5 kg m−3 at about 60 m, respectively. In contrast, the maximum change of T, S and σθ in the composite AE reaches 1.6 °C (about 110 m), −0.1 psu (about 70 m), and −0.5 kg m−3 (about 90 m), respectively. The maximum swirl velocity within the composite CE and AE reaches 0.3 m s−1. The zonal freshwater transport induced by CEs and AEs is (373.6 ± 9.7)×103 m3 s−1 and (384.2 ± 10.8)×103 m3 s−1, respectively, contributing up to (8.5 ± 0.2)% and (8.7 ± 0.2)% of the annual mean transport through the Luzon Strait

Dynamics of the Loop Current System and Its Effects on Surface and Subsurface Properties in the Gulf of Mexico

Surface circulation in the Gulf of Mexico is dominated by the Loop Current System (LCS), including the Loop Current (LC) and its associated eddies. The Gulf of Mexico (GoM) also displays long-term surface gradients of temperature and salinity due to climatological features including the intrusion of warm, saline waters from the Caribbean Sea and the seasonal deposition of freshwater from the Mississippi River System caused by seasonal increases in snow melt and precipitation over the watershed. This research aims to increase the understanding of the LCS through the investigation of its relationship with these surface gradients. A classification system of LCS interaction with seasonallypresent freshwater is developed to explore how the LCS can deform salinity gradients within the Gulf. Surface advective freshwater flux is calculated by combining satellitederived measurements of sea level anomalies with sea surface salinity from the recent satellite salinity missions, ESA’s Soil Moisture and Ocean Salinity (SMOS) and NASA’s Soil Moisture Active Passive (SMAP), in order to observe lateral movement of low-salinity water throughout the Gulf. Through interaction with the LCS, riverine-sourced freshwater can have numerous fates and redistribution patterns throughout the GoM. The LCS shares the GoM surface with a large mesoscale eddy field, which is investigated through the application of an automatic eddy-tracking algorithm to absolute dynamic topography derived from satellite altimetry and sea surface height from HYbrid Coordinate Ocean Model (HYCOM) simulations. The spatial distribution and temporal evolution of eddy properties, as well as the variation of these surface and subsurface properties between the eastern and western Gulf are analyzed. Surface eddy composite analysis reveals that long-term gradients present in the GoM greatly affect eddy salinity, temperature, and chlorophyll-a concentrations. HYCOM simulations are verified with insitu Argo profile data in order to investigate mean eddy vertical structure, which varies greatly between the eastern and western Gulf of Mexico. The classifications of LCS interaction with low-salinity water presented here offer a new explanation for the multiple fates of Mississippi River waters, and composite analysis of surface and subsurface eddy properties provides an innovative and complete picture of the GoM mesoscale eddy field