Water transport in the Bosphorus Straits estimated from hydro-meteorological and altimeter data: seasonal to decadal variability

Abstract

TOPEX/Poseidon (T/P) altimeter data for the period 1993–1997 and their correlation with available precipitation, evaporation and river runoff data are analysed with the aim to study the variability of sea level and water balance in the Black Sea. The difference between the time rate of change of basin volume estimated from altimeter and fresh water flux data is used as a measure of the vertically integrated transport through the Bosphorus Strait. The errors in the transport resulting from the use of tide gauge data when estimating the variations of basin volume are objectively quantified using sea level from T/P data as reference measurements. Then, from the long-term tide gauge and hydro-meteorological data series for the period 1923–1997, we derive the variability of basin volume and transport in the Bosphorus Strait. It is found that the main signal in the transport is the seasonal one, with maximum values in March–April and minimum in August. The amplitude of this signal is ∼2/3 of the amplitude of the net fresh water flux. In low frequency range, the oscillations with periods 10 and 4 years have significant amplitudes. However, the ratio between the magnitude of oscillations in the forcing (fresh water flux) and the response (transport in the strait) tends to unity. This indicates that the resistance of strait to climatic variability with interannual and decadal time scales is negligible. It is demonstrated that the available data present a valuable source of information when calibrating parameterizations of straits transport based on theoretical developments.