A 6.5-year continuous record of sea surface salinity and seawater isotopic composition at Harbour of Ishigaki Island, southwest Japan

Abstract

We produced continuous records of sea surface salinity and isotopic composition from 1998 to 2004 at Ishigaki Island, southwest Japan, and found clear seasonal variations in salinity and oxygen isotopic composition and increasing trends of them after 1999. These increasing trends could be principally due to the decreasing difference between local precipitation (P) and evaporation (E), as a result of the reduction of horizontal vapour transport from adjacent oceans. When samples collected in heavy rainfall events were excluded, the average Δδ¹⁸O/Δ salinity slope was obtained as 0.31, 0.35 in summer and 0.28 in winter. Estimated E/P ratios based on the isotopic box model are in good agreement with the ratios of independently estimated E to observed P.

^†Updated paper: originally presented on the IAEA International Symposium “Quality Assurance for Analytical Methods in Isotope Hydrology” (August 2004, Vienna).

Keywords:

• evaporation
• isotope hydrology
• hydrogen-2
• Japan
• oxygen-18
• precipitation
• salinity
• seawater

Acknowledgements

This study was partly supported by the Center Research Project of Hydrospheric Atmospheric Research Center, Nagoya University.

Notes

^†Updated paper: originally presented on the IAEA International Symposium “Quality Assurance for Analytical Methods in Isotope Hydrology” (August 2004, Vienna).