Observation of summertime upwelling off the eastern and northeastern coasts of Hainan Island, China

Evaluation of Water Residence Time, Submarine Groundwater Discharge, and Maximum New Production Supported by Groundwater Borne Nutrients in a Coastal Upwelling Shelf System

“…The sampling period is in summer and therefore, this study does not consider the mixing process induced by alongshore currents. This assumption is reasonable because previous studies have shown that currents perpendicular to the coastline other than alongshore current is dominant in HEU during the summertime (Hu & Wang, ; Jing et al, ; Lin et al, ; J. Su et al, ). Based on oceanographic settings and dominant radium sources, two scenarios are considered when deriving water residence time of upper layer of HEU with radium isotopes: with and without influences of coastal upwelling.…”

“…The low temperature zone expands at 25 m and reaches the maximum at the depth of 50 m. At the layers of 75 and 100 m, the lower temperature zones are reduced to the northeastern zone. The lower temperature zones at the nearshore coastal areas are mainly caused by the Ekman transport driven by alongshore wind during the summer seasons, and the lower temperature core at the northeastern coastal was speculated to be resulted from Ekman pump driven by the cyclonic wind stress curl (Jing et al, ; Lin et al, ; J. Su et al, ). Salinity and density anomaly gradually decline with depths in each layer.…”

“…The higher salinity and density zones are mostly located at the northeastern areas off Hainan Island at the depth of 5 m, with a zonal salinity and density anomaly of 33.8 psu and 20.8 kg m −3 , respectively (Figures f and k). The relatively lower salinity zone close to the coastal line could be a result of terrestrial runoff and SGD (Lin et al, ; J. Su et al, ). The high salinity zone expands to most areas of inner shelf at the depths of 50 m, indicating intensified upwelling.…”

“…The most important physical oceanographic feature for the eastern Hainan shelf is summertime coastal upwelling off eastern Hainan, or Hainan eastern upwelling (HEU). HEU is formed due to the synergistic effect alongshore wind, wind stress curl‐induced Ekman pumping, and the alongshore topographic variations (Hu & Wang, ; Jing et al, ; Lin et al, ; J. Su et al, ). The coastal upwelling, as a key physical driving force on nutrients and phytoplankton, will exert a profound impact on the oceanic primary productivity (Zhang et al, ).…”

Progress on upwelling studies in the China seas

“…Moreover, the wind stress curl‐induced Ekman pumping is considered to be another crucial effect generating the coastal upwelling off eastern Hainan Island and eastern Leizhou Peninsula [ Jing et al ., ]. Recently, the upwelling has been classified into three patterns, i.e., intensified upwelling off the eastern coast of Hainan Island (HEU), intensified upwelling off the northeastern coast of Hainan Island (HNEU), and both HEU and HNEU in 1 day [ Lin et al ., ]. Reanalysis data and satellite data have shown that the HEU is mainly driven by southwesterly wind and is not affected remarkably by fresh water, whereas the HNEU is associated with the prevailing southeasterly wind and can be limited in the lower layer when it is covered by fresh water.…”