Temperature and salinity records of the Tyrrhenian Sea during the last 18,000 years
Abstract We have used the modern analogue technique to derive sea surface temperature (SST) records of the last 18,000 years from two well-dated deep-sea cores recovered in the Tyrrhenian Sea. Results show two major cooling events synchronous with the European and North Atlantic Oldest and Younger Dryas events. A later cooling of lower amplitude is observed between about 8000 and 4500 yr BP. Tyrrhenian SSTs were similar to those of the upper Holocene only during the Bolling/Allerod event and at the beginning of the Holocene. We compared the SST and the planktonic foraminiferal oxygen isotope records to estimate the surface salinity variations. Our reconstruction shows that salinity decreased in the Tyrrhenian Sea during the three cold events, whereas high SSTs correlate with high salinities. During most of the last 18,000 years. Tyrrhenian Sea salinity variations were similar to those of the North Atlantic Ocean near the entrance of the Mediterranean Sea. The salinity gradient between the two basins was thus constant, indicating that the western Mediterranean circulation pattern and the freshwater budget were not significantly different from the modern one. The case was however different during the middle Holocene, when the strong salinity decrease associated with the sapropel deposit in the eastern Mediterranean basin had no equivalent in the North Atlantic Ocean. This peculiar event can only be explained by a local climatic change and an increase of precipitation.