Manifestation of internal waves in the Southern Caspian Sea using satellite imagery

Abstract

Iran's South Caspian coast is an important agricultural hotspot and densely populated area that attracts about 20 million domestic tourists in summer. Therefore, not only the coastal area ecosystem of the South Caspian Sea (SCS) but also their marine ecosystem is exposed to different environmental pollution. The ecosystem of the SCS especially in the onshore area strongly affected by Internal Waves (IWs) dynamics. IWs can capture, concentrate and transport, floating plastic debris, larvae, contaminants, and toxic pollutants in this basin. Therefore, detecting and zoning the SCS for IWs is critical to the management and protection of this enclosed basin. Measured data obtained from CTD and satellite imagery archives from Landsat 7, 8, and Sentinel-2 have been used to analyze and manifest IWs. Analysis and comparison of different satellite images reveal that the maximum wavelength of the IWs packet was about 400 m with a crest length of 18,000 m. However, the minimum packet had a wavelength of about 20 m with a crest length of 360 m. Based on the occurrence of IWs extracted by edge-finding algorithms on satellite images, the SCS can be divided into six original zones. Four zones of them located near the coastal line where freshwater rivers discharge to the sea in the rainy season and two other zones are in the deep water, which form under the dominant sea surface wind regime and sharp changing of bathymetry.