The planktonic foraminifera Globorotalia truncatulinoides in Central - Western Mediterranean Sea during the Little Ice Age

Abstract

The study of the climate changes of the last centuries allows comparison of data from historical documents, instrumental and paleodata records with multi-decadal variability arising from external forcing and internal climate variability. In this framework, the marine fossil records represent a fantastic archive to document the climatic variability over the last 500 yrs. In this framework, Globorotalia truncatulinoides oscillations have been recorded from several marine sediment cores collected in the central and western Mediterranean Sea. G. truncatulinoides represents a deep dwelling winter species in the Mediterranean Sea and its life-cycle is characterized by a vertical migration in the water column. The abundances of this species over the last 500 yrs demonstrates its potential value as bio-indicator of particular oceanographic condition during the Maunder Minimum (MM) event of the Little Ice Age (LIA). The comparison between the G. truncatulinoides abundance patterns of the Balearic Basin, central and south Tyrrhenian Sea and central and eastern Sicily Channel allows to highlight a similar response of this species during the MM event in the central-western Mediterranean Sea. The ecological meanings of this species and its peculiar high abundance percentage values in the total assemblages suggest the development of enhanced vertical mixing conditions during MM winter season with a strong advection of nutrients from the nutrient-rich deeper layers and enhances the productivity levels in the mixed layer. The intensified vertical mixing could be linked to persistence of an atmospheric blocking event recorded by several authors during the MM. In fact, this time-interval is characterized by an atmospheric blocking event. These particular climatic conditions could be responsible of intense deep vertical mixing phenomenon during the winter season producing the ideal ecological conditions for G. truncatulinoides proliferation. In addition, we suggest that maximum abundance of G. truncatulinoides left coiled is a response to more active dense water formation within the Mediterranean Sea during a cold time-period such as the MM. This research has been financially supported by the ERC-Consolidator TIMED project (REP-683237).