APPLICATION OF RADAR ALTIMETRY AND MULTI TEMPORAL SATELLITE IMAGERY TO CONFIRM CLIMATIC CHANGES AFFECTING WATER LEVEL OF CASPIAN SEA

The Caspian Sea (CS) is the world's largest lake with a water level of 27 m below world ocean level and surrounded by Russian Federation, Azerbaijan, Iran, Turkmenistan, and Kazakhstan. Instrumental records of the CS show that water levels are fluctuating with cyclical pattern. It is suggested that solely climatic effects (runoff, precipitation, and evaporation) could control the water balance in CS. Water level fluctuations are also attributed to subsidence, uplift and related seismic activity in the southern and central part of the CS and surrounding areas, as well as a correlation of smoothed solar cycle (number of sunspots) with long-term oscillations in Caspian Sea. Groundwater and mud volcano activities can also contribute to the water level changes, even though their effects on water budget of CS have not been well studied. The aim of this study is to test the hypothesis that water level fluctuations in CS is caused by climatic effects. In order to test this hypothesis, radar altimetry and multi temporal satellite imageries will be utilized. Surface heights of CS will be estimated using radar altimetry data from ERS-1 and ERS-2 (European Space Agency), Topex/Poseidon (T/P) for anniversary dates starting from 1992 to 2007. While low resolution Advanced Very High Resolution Radiometer (AVHRR) images will be utilized for whole caspian Sea for rough estimation of shoreline changes, higher resolution Landsat TM and ASTER multi temporal images will be used for more detailed analysis of shoreline changes. Sea surface heights (SSHs) obtained from radar altimetry will be projected to coastal areas to check whether the SSHs will fit the strandlines or not to evalute the effects of climate. Two AVHRR images taken on June 20, 1999 and June 21, 1997 respectively, were chosen to analyze differences in shorelines. Calculation of CS surface areas with GIS showed that larger sea surface area was obtained from the image of 1997, indicating water level decline between 1997 and 1999.