Seasonal and Interannual Variability of Water Exchange in the Strait of Istanbul

Temperature and salinity distribution and volume fluxes through the Strait of Istanbul were analyzed using the long-term monthly time series of temperature-salinity (1996-2010) and current profiles (1999-2010), collected from both ends of the strait. While the annual cycle of the upper layer temperature, with the minima in February and maxima in August, reflects the influence of air temperature with a near monthly phase shift, the annual cycle of the upper layer salinity, with the lowest values observed between April and September is mostly affected by the river discharge into the Western Black Sea. The seasonal variations of the lower layer temperature and salinity in the Strait of Istanbul are mostly influenced by flow blockages. Inversely proportional upper and lower layer volume fluxes indicate strong seasonal variations with the minimum and maximum values in April and October, respectively. The annual average upper and lower layer volume fluxes calculated from the high resolution dataset are 404 km(3)y(-1) and 250 km(3)y(-1) at the north end, and 430 km(3)y(-1) and 245 km(3)y(-1) at the south end of the strait, respectively

Daily variations in stratification in Izmit Bay

We studied the diurnal variation of stratification in Izmit Bay with temperature and current velocity, and investigated the influence of atmospheric conditions. In the east of the bay entrance, 10-min temperature and hourly current measurements were made between the dates of 4 February 2015 and 24 April 2015, down to about 40 m depth in the water column. In addition to this, hourly temperature and salinity with depth data were collected between the dates of 4 and 7 February 2015 by a research vessel. The meteorological parameters for the atmospheric conditions were obtained from the closest weather stations (Yalova, Cinarcik, and Gebze). Thermocline depth varied between 20 and 30 m with instant changes at 6 to 35 m of depth due to strong wind conditions with 3 days of time delay. The south-westerly current directions were found in both layers, but the current speed decayed with depth. The high buoyancy frequency due to strong stratification decreased in strong wind and shear dominated the mixing process. Air pressure, air temperature, north-south component of wind and sea level had a semidiurnal cycle. A high-frequency measurement in a 2-layer system is highly significant to understand, explain, and determine the cause and effect relationships of hydrographic processes

Seasonal variation of suspended particulate matter in two-layered Izmit Bay, Turkey

The spatial and temporal distribution of suspended particulate matter (SPM) concentration in Izmit Bay (Sea of Marmara) were studied in order to examine the prevailing transport mechanisms under varying seasonal hydrographical conditions. The prevailing current system of the Bay occurs in two opposite directions and changes seasonally, flowing into the Bay as a lower layer and flowing out to the Sea of Marmara as an upper layer in autumn and winter. SPM concentrations and distribution pattern of both upper and lower water layers display variations throughout the year, reflecting a seasonal cycle and variability of the circulation and stratification of two water layers seems to control the vertical and spatial distribution of SPM in Izmit Bay. The SPM concentration of the lower layer is higher than that of the upper layer with an increase in intensity of the pycnocline in summer. Homogeneous vertical distribution of SPM during February and March is supported by the weak stratification of the two layers. SPM transportation from Izmit Bay to the open sea occurs in winter, whereas it is carried to interior of the Bay from central to eastern basins in summer. Both the grain size distribution of the bottom sediments and the temporal-spatial variation of SPM content of the water column indicate that the transportation and depositional conditions are different in the three basins. Predominantly fine-grained-sized bottom sediments are deposited in the central and eastern basins due to the reduced current velocities in the lower layer. The western basin is subjected to deposition of sediments with various size, from both the central basin and the Sea of Marmara. (C) 1999 Academic Press

Summer Current Conditions in the Gokova Bay

The hydrography and circulation characteristics of the Gokova Bay were examined by using ADCP and CTD data collected in June 2005, May and July 2006. The influence of the meteorological conditions was also considered together with the oceanographic data