Author(s)

Nur Hidayah Roseli¹, Mohd Fadzil Akhir^1*, Mohd Lokman Husain¹, Fredolin Tangang², Azizi Ali¹

¹Institute of Oceanography and Environment, Universiti Malaysia Terengganu, Kuala Terengganu, Malaysia.
²Research Centre for Tropical Climate Change System, National University of Malaysia, Bangi, Malaysia.

CTD data obtained from two oceanographic cruises during June and October 2012 were used to define the water mass characteristics and degree of stratification at the shallow Sunda shelf located at the southern South China Sea. The water masses during both cruises showed characteristics similar (southwest monsoon) to those observed in the adjacent regions. A clustering method was used in which three water masses were classified from the composite dataset. There are WM1 (T 29°C - 31°C, S 32 - 33.5 psu, & σ_T, ~19.5 - 20.7 kg/m³), WM2 (T 25°C - 29°C, S 32.8 - 33.8 psu, & σ_T, ~22.3 - 23 kg/m³) and WM3 (T 23°C - 25°C, S33.5 - 34.0, & σ_T ~22.3 - 23.3 kg/m³). Even though the water masses found were characterized under southwest monsoon characteristics, the degrees of stratification obtained varied between these cruises. The stability of the stratification also plays roles in the distribution of the water masses in the water column. WM2 was found in thermocline layer and most dominant in June compared to in October. In June, WM3 was found under the thermocline layer and absent in October. The stable thermocline caused the denser WM3 cannot mixed with WM2. Higher temperatures and weaker winds during June may have caused the strong stratification, while decreasing temperature and stronger winds of an upcoming northeast monsoon enhanced the vertical mixing during October.

Water Masses, Stratification, Brunt-Vaisala Frequency, Sunda, Shelf, South China Sea

Roseli, N. , Akhir, M. , Husain, M. , Tangang, F. and Ali, A. (2015) Water Mass Characteristics and Stratification at the Shallow Sunda Shelf of Southern South China Sea. Open Journal of Marine Science, 5, 455-467. doi: 10.4236/ojms.2015.54036.