sea-level rose 13 centimetre during the whole twentieth century, the Caspian sea rose 13 centimetre each year in the period between 1977 and 1995. This means that Caspian coasts had to cope with a sudden sea-level rise of three metres in twenty years. The years before, however, between 1929 and 1977 Caspian sea level fell three metres. Caspian sea level change is forced by global processes such as the North Atlantic Oscillation, solar forcing, deglaciation and tectonics.
The Volga river accounts for about 80% for the inflow of water in the sea, the remainder being formed by seven other smaller rivers and inflow from groundwater, and Caspian sea-level changes show a statistically significant correlation with secular changes in the discharge of the Volga river. These in turn have been shown to record variations in precipitation over the Volga drainage basin, related to variations in the amount of Atlantic depressions that reach the Russian mainland. Past Caspian sea level therefore offers a measure for past precipitation changes and therefore also of past changes in global climate.
Rapid sea-level fluctuations have taken place in the Caspian sea since it became a closed basin about 5.5 million years ago. The Caspian sea, now at -27 m below oceanic sea level, is known to have had high-stands of +50 m and (probably) -80 m in the last 100,000 years, and even higher high-stands further afield.
To help us in understanding the pace of global change in the northern hemisphere in the past establishing a precise Caspian sea-level curve for the recent geological past is important. The topic will be treated at an international conference on rapid sea-level change 2-9 May 2007 in Iran and again explicitly 8-17 September 2007 in Russia with the following objectives:
Sea level change is one of the most pervasive environmental processes that have affected humanity in the past and will continue to do so in the future. This meeting aims to discuss natural and man-made causes and consequences of sea-level change, at a site which has experienced rapid sea-level change at a rate a hundred times that of global eustasy during the last century: the Caspian Sea.
The North Atlantic oscillation is a climatic phenomenon in the North Atlantic Ocean of fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores high. Through east-west rocking motions of the Icelandic Low and the Azores high, it controls the strength and direction of westerly winds and storm tracks across the North Atlantic. It is related to and highly correlated with the Arctic oscillation.
Similar to the El Niño phenomenon in the Pacific Ocean, the North Atlantic oscillation is one of the most important drivers of climate fluctuations in the North Atlantic and surrounding continents. The relative strengths and positions of the Icelandic low-pressure system and the Azores high-pressure system vary from year to year and this variation is known as the NAO.
Yearly NAO indexes.
Source: graph drawn by Hanno using data published on the web by J.W. Hurrell (Climate Analysis Section, National Center for Atmospheric Research, Boulder, Colorado, USA) as "Climate indices" (http://www.cgd.ucar.edu/cas/jhurrell/indices.html)
PS: The paths taken by Icelandic lows and Azores highs are determined by the path taken by the jet stream - see http://my.opera.com/nielsol/blog/jet-stream.