South Caspian vertical circulation during rapid sea level rise and fall

Abstract

The Caspian Sea as the largest land-locked water body is very sensitive to the environmental changes. The rise and fall of the Caspian Sea level has significant impact on the environment and coastal communities. Using extensive deep water measurements in the south Caspian Sea, we have examined the role of sea level changes on the vertical water exchange.  While the deep water ventilation happened during sea level fall (70s of 20 century), coastal lagoon expansion and marine stagnant circulation state were the major impacts during rapid sea level rise (1980-1995). The marine environment however benefits the rapid sea level fall.  During sea level fall, vertical circulation penetrates deeper and faster which distributes oxygen and nutrient more effectively in the water column. It provides the condition for enhanced bio-productivity. However, the current global warming could prevent the impact of lowstand to faster circulation. The present rapid sea level fall displays new impacts on the marine environment, reflecting as hypoxia.