Annual Report 2009-2010 - Ministry Of Earth Sciences

Fig. 4.8: Variations in the mesozooplankton
biomass (ml.m-3) in the fronts and zones.
Uniform biomass can be seen at 4 major zones
main zones, STZ, STFZ, SAZ, PFZ, supported almost
identical standing stocks of mesozooplankton
during the austral summer (Fig. 4.8).
Oxygen isotope and salinity variations
A combined study of stable oxygen isotopes δ 18 O
and salinity of surface ocean waters collected
from the Southern Indian Ocean during the late
austral summer and early fall helped to trace
atmospheric and oceanic processes. Near the
equator, a very clear signature of the domination
of evaporation-precipitation process was seen,
while a precipitation dominated zone was located
between two evaporation dominated zones south
of the equator. The signature of the Agulhas Front
(AF) and the Subtropical Front (STF), recognisable
by the sharp decrease in salinity and dissolved
oxygen in the surface waters were identified at
41°S and 44°S in February. In March, these two
fronts had merged and were located at 41°S.
follows the normal continental shelf sequence, i.e.
shallower depth sediments consisting of gravel,
pebbles+ sand, followed in the deeper parts by
sand, silty sand and clayey sand. The existence
of Oolites in the sand part of the sediment at 220
to 420 m water depth has also been observed
(Fig. 4.9).
Under a project linked to IPY, the monitoring
of the upper ocean circulation, transport and
water masses between Africa and Antarctica was
carried out by NCAOR. Expendable Conductivity
Temperature and Depth (XCTD) probes were
utilised by which the temperature and conductivity
profiles in the upper 1000m of the water column
were obtained. Eighty observations were made
along the cruise track from Cape Town, South
Africa to the Larsemann Hills in Antarctica.
Fig. 4.9: Light yellow and light white coloured
Oolites off Enderbyland shelf, Antarctica (left
panel). Cross section of an Oolite showing
yellow outer rim enveloping translucent white
inner core/nucleus (right panel).
Vertical structure of temperature
Vertical profiles of temperature along 57°30’E
meridional section at 35°31’S, 42°20’S, 47°40’S
and 54°S to understand variability of temperature
and salinity from different regions have been
compared.
Sedimentology of Enderbyland
Sedimentological analyses carried out at the shelf
of the Enderby land showed that the shelf, texturally
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