25. Implications of Climate Change for Marginal and Inland Seas

As confined water bodies, the semi-enclosed and inland seas are particularly vulnerable to the global change. The climate change trends observed in the marginal seas reflect a spectrum of interactions between the ocean, atmosphere and the continents, and this is why their responses are generally more complex than those characteristic for the open ocean. In this article, we start with the ongoing climate change processes in the deep ocean versus the semi-enclosed and marginal seas, and then discuss case studies based on the recent data collected from marginal or inland seas, namely, the Black Sea, the Kara Sea, and the Aral Sea. We show, in particular, that over much of the last few decades, the sea surface temperature changes in the Black Sea had the opposite sign compared to those in the world ocean. The sea temperature within the uppermost oxygenized layer of the Black Sea exhibited significant correlation with North Atlantic Oscillation. Furthermore, we show that in the Kara Sea, which is poorly covered by observational data, pH is likely to have been growing during the last two decades, in contrast with the global acidification trends, possibly, in connection with the long-term variability of fluvial runoffs from Yenisey and Ob rivers modulated by wind forcing. The Aral Sea represents an extreme response of a large inland water body to climate change and anthropogenic impacts. The Aral Sea level has dropped over 26 m since 1960, and its volume decreased by a factor of 10. The desiccation was primarily caused by anthropogenic diversions of water from the tributary rivers, but about 30% of the level drop was associated with climate change at the regional scale. We discuss the ongoing changes in the ionic salt composition of the Aral Sea water accompanying the desiccation.