Physical Oceanography

This study focuses on the influence of extreme hydrological events on the water quality of the Strait of Istanbul (Bosphorus); a stratified waterway, polluted by sewage outfalls and non-point sources. Monthly collected water quality parameters (nitrate + nitrite, ortho–phosphate, silicate, dissolved oxygen, total suspended solids, chlorophyll-a and fecal indicator bacteria (fecal coliform and enterococci)) were evaluated together with the hydrological data (salinity, temperature and current flow) for one year. Two blockage events, identified as extreme conditions, were detected during the study; a lower layer blockage in February 2003 and an upper layer blockage in October 2003.

During the lower layer blockage, the volume fluxes of the upper layer significantly increased to 28,140 m3 s- 1 and the lower layer almost stopped flowing (19 m3 s- 1). The dissolved oxidative nitrogen, ortho-phosphate and silicate inputs outflowing from the Black Sea were 117, 17.6, and 309 tonnes which were 3, 2, and 4 times the average daily fluxes respectively, resulting in 4.5 fold increase in daily chlorophyll-a, in addition to enhancement of fecal indicator bacteria contamination in the sea surface flow.

During the upper layer blockage, the volume flux of the upper layer was 3,837 m3 s- 1 and the counter flow reached 24,985 m3 s- 1 at the northern exit of the Strait of Istanbul resulting in 2.7 fold increase in the mean bottom flow. The daily exports of nutrients, total suspended solid and dissolved oxygen by the lower layer flow increased by at least 2 fold compared to the mass fluxes estimated from the seasonal/annual means of volume flux and concentrations. On the other hand, fecal indicator bacteria flux by the lower layer inflow to the Black Sea decreased by at least 2 fold compared to the mean daily flux. These results show that the material exchange between the Marmara and the Black seas become more important during blockage events.

Purpose . The aim of the work is to develop, construct and test the experimental model for the ground-to-space monitoring of anthropogenic impacts on the Crimean coast using satellite and surface data. The system is intended to obtain significant parameters of marine environment required for revealing the anthropogenic impact sources, developing feasible recommendations on sustainable nature management and decreasing the anthropogenic load on marine ecosystems. Methods and Results . The paper represents description of the monitoring structure and the equipment focused on the ground segment of the system applied in the Marine Hydrophysical Institute of RAS, as well as the example of its implementation in monitoring the Crimean coastal water areas. Discussed is the concept of the ground-to-space monitoring of anthropogenic impacts on the coastal water areas which constitutes a foundation of the proposed system. The ground sub-satellite segment of the monitoring system intended for col...

CORTEZ, Rafael Henrique de Castro. Oceanographic characterization of a tidal inlet and the
nearby coastal zone: Barra de Guaratiba inlet, Sepetiba Bay, RJ. 2014. 131 f. Dissertação
(Mestrado em Oceanografia) – Faculdade de Oceanografia, Universidade do Estado do Rio de
Janeiro, Rio de Janeiro, 2014.
On the eastern boundary of Sepetiba bay lies a tidal channel system that debouches
into the ocean through a 4m-deep channel located in Barra de Guaratiba, between Marambaia
barrier island and the continent. With the main goal of contributing new information about the
oceanographic characteristics of this poorly studied area, sampling campaigns consisting of
anchor stations and transects located in the nearby coastal area. Two anchor stations placed at
the extremities of the tidal channel system, at its inner limit and at the Barra de Guaratiba
mouth, were simultaneously occupied for 50 and 25 hours, respectively, in October/2013 and
February/2014. Measurements were conducted under spring tide conditions and included
water level, currents, water properties (temperature, conductivity, transmissivity, fluorescence
and dissolved oxygen), suspended particulate concentration (SPM) and surface sediment.
Additionally, three transects extending for roughly 800m off the Barra de Guaratiba tidal
channel mouth were sampled in December/2013. The results have shown that the Barra de
Guaratiba tidal channel is highly dynamic with current speeds reaching 1.8 m·s-1 in
October/2013, when the passage of a cold front induced strong SW winds and increased
rainfall. During this same campaign a series of eddies were seen entering the channel,
carrying high concentrations (~9 g·L-1) of suspended sand. In February/2014, under
fairweather conditions, current speed reached 1.4 m·s-1. Both, in October/2013 and
February/2014, the strongest currents were measured during the time of current direction
inversion, roughly 1:45 hr before each high water, when water flows towards the ocean while
water level continuously rises. This counterintuitive behavior is possibly related to pressure
gradients developed inside Sepetiba bay due to the large volume of water that enters the bay
through its main connection with the sea at its western boundary, forcing the water flow
through the anastomosed tidal channels that discharge through Barra de Guaratiba. Temporal
variation of SPM concentration followed the current speed pattern, reaching the highest
values during ebb tides, when flows are more intense, suggesting local ressuspension and
advection of turbid waters from the bay. Barra de Guaratiba tidal channel also influences the
nearby coastal ocean as attested by the variability of the water properties measured in
December/2013, particularly along the transect that follows its main orientation. Moreover,
surface sediment grain size distribution also indicates the channel’s influence through the
increased occurrence of medium sands, similar to those found inside the channel, from
approximately 500m off the channel’s mouth. Winds play an important role in the channel’s
dynamics, intensifying the ebb/flood currents when aligned with their orientation. South
Atlantic Central Water (SACW) was found in the sampling campaigns inside Barra de
Guaratiba channel (February/2014) and in the coastal area (December/2013), when it was
detected close to the bottom of the outermost stations.
Keywords: Circulation. Suspended solids. Currents. Tides.

This manuscript study’s the mechanics of suspended sediment transport in Macuse Estuary River in Mozambique, East Africa. The methodological approach was based on geomorphologic and oceanographic surveys covering 42 georeferenced stations. We conducted in situ tide and current measurements with a RBRduo tidal gauge and current-meter moored at the Macuse Harbour. The fi eldwork comprised data collection in two periods, from 17th to 19th November 2013 and from 16th to 21st November 2014. Water samples were collected in a Niskin bottle for suspended sediment analysis. The sediments were fi ltered using a 47μm fi berglass and a vacuum pump, which were weighted in a highly precise electronic scale. Hydrodynamic simulations were conducted using a three-dimensional numerical model with the ELCOM-CAEDYM covering the period of in situ data collection. The calibration and validation of simulated results were performed through comparisons of fi eld data and the simulated results. The in
situ and modeled results indicated tides of 4.0 m in height that generated tidal currents between -0.8 m/s and 1.2 m/s. Its cyclic hydrodynamic regime defi ned the mechanics of sediment transport in suspension of the silt and fine sand group by dragging process. The concentrations of silt and very fi ne sand obtained through the implementation of the ELCOM-CAEDYM model indicated fractions between ~ 100 mg/l and ~ 300 mg/l during the ebb and fl ood
tides. These concentrations suggest sedimentation in the riverbed by silt with a fl ow of less than 0,1 cm/s and of very fi ne sand with a fl ow of less than 10 cm/s. The sedimentation in the bed can occur by very fi ne sand fractions that may cause signifi cant modifi cations in the geomorphological confi guration of the Macuse Estuary River and
technical port operations.