Black Sea which are largely responsible for regional precipitation inputs and influence Mediterranean Sea Surface Temperatures (SST's). The relative strength of these systems also limits the amount of cold air arriving from northern regions during winter. Other influencing factors include the regional topography, as depressions and storms systems arriving from the Mediterranean are funneled through the low land around the Bosphorus, Pontic and Caucasus mountain ranges acting as wave guides, limiting the speed and paths of cyclones passing through the region. There are some islands in the Black sea that belong to Bulgaria, Romania, Turkey, and Ukraine: The Black Sea is connected
Caspian Sea region. There are similar tensions between Azerbaijan and Turkmenistan (the latter claims that the former has pumped more oil than agreed from a field, recognized by both parties as shared). The Caspian littoral states' meeting in 2007 signed an agreement that bars any ship not flying the national flag of a littoral state from entering the sea. Negotiations among the five littoral states have been ongoing, amidst ebbs and flows, for the past 20 years, with some degree of progress being made at the fourth Caspian Summit held in Astrakhan in 2014. The Caspian Summit is a head of state-level