Abstract. The seasonal and interannual variations of the barrier layer
thickness (BLT) in the tropical Indian Ocean (TIO) is investigated in this
study using the Simple Ocean Data Assimilation version 3 (SODA v3) ocean
reanalysis dataset. Analysis of this study suggests energetic but divergent
seasonal variabilities of BLT in the western TIO (5∘ N–12∘ S, 55–75∘ E) and the eastern TIO
(5∘ N–12∘ S, 85–100∘ E). For
instance, the thicker barrier layer (BL) is observed in the western TIO
during boreal winter as a result of decreasing sea surface salinity (SSS)
and deeper thermocline, which are associated with the intrusion of
freshwater flux and the weakened upwelling, respectively. On the contrary,
the variation of BLT in the eastern TIO mainly corresponds to the variation
in thermocline depth in all seasons. The interannual variability of BLT with
the Indian Ocean Dipole (IOD) and El Niño–Southern Oscillation (ENSO) is
explored. During the mature phase of positive IOD events, a thinner BL in the
eastern TIO is attributed to the shallower thermocline, while a thicker BL
appears in the western TIO due to deeper thermocline and fresher surface
water. During negative IOD events, the thicker BL only occurs in the eastern
TIO, corresponding to the deeper thermocline. During ENSO events, prominent
BLT patterns are observed in the western TIO corresponding to two different
physical processes during the developing and decaying phase of El Niño
events. During the developing phase of El Niño events, the thicker BL in the
western TIO is associated with deepening thermocline induced by the westward
Rossby wave. During the decaying phase of El Niño events, the
thermocline is weakly deepening, while the BLT reaches its maxima induced by
the decreasing SSS.
Estimation of the barrier layer thickness in the Indian Ocean using Aquarius Salinity