TITLE:
Water Mass Characteristics and Stratification at the Shallow Sunda Shelf of Southern South China Sea
AUTHORS:
Nur Hidayah Roseli, Mohd Fadzil Akhir, Mohd Lokman Husain, Fredolin Tangang, Azizi Ali
KEYWORDS:
Water Masses, Stratification, Brunt-Vaisala Frequency, Sunda, Shelf, South China Sea
JOURNAL NAME:
Open Journal of Marine Science,
Vol.5 No.4,
October
27,
2015
ABSTRACT: 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, & σT, ~19.5 - 20.7
kg/m3), WM2 (T 25°C - 29°C, S 32.8 - 33.8 psu, & σT, ~22.3 - 23 kg/m3)
and WM3 (T 23°C - 25°C, S33.5 - 34.0, & σT ~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.