LANG Lin, LIU Jian-an, ZHONG Qiang-qiang, DU Jin-zhou. Water mixing in the northern slope of the South China Sea as traced by 226Ra and 228Ra[J]. Chinese Journal of MARINE ENVIRONMENTAL SCIENCE, 2020, 39(4): 511-521. DOI: 10.12111/j.mes.20190025
Citation: LANG Lin, LIU Jian-an, ZHONG Qiang-qiang, DU Jin-zhou. Water mixing in the northern slope of the South China Sea as traced by 226Ra and 228Ra[J]. Chinese Journal of MARINE ENVIRONMENTAL SCIENCE, 2020, 39(4): 511-521. DOI: 10.12111/j.mes.20190025

Water mixing in the northern slope of the South China Sea as traced by 226Ra and 228Ra

  • Radium isotopes were important tracers for water transport and mixing processes. We investigated the distribution of 226Ra and 228Ra in the northern slope of the South China Sea (SCS) during spring based on a cruise conducted in March 2017. The results proved that the activities of 226Ra in surface water varied from 6.4 to 10.7 dpm/100 L, and those of 228Ra varied from 4.6 to 26.0 dpm/100 L. The 226Ra and 228Ra activities, temperature and salinity in the surface seawater reflected that the surface water in the northern SCS was mainly composed of two water masses, namely the SCS water and the Kuroshio branch water. The proportion ranges of the two water masses in study area was 0.13~1.05 and −0.05~ 0.87, respectively. The activity ranges of 226Ra and 228Ra in sea water column were 5.9~29.7 dpm/100 L and 2.6~6.5 dpm/100 L. Using a steady-state hypothesis and the two-box model of 226Ra and 228Ra, the residence time of seawater below 1500 m in the northern SCS was estimated to be approximately 14~61 years.
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