Variations in Mediterranean–Atlantic exchange across the late Pliocene climate transition

Abstract

Abstract. Mediterranean-Atlantic exchange through the Strait of Gibraltar plays a significant role in the global oceanclimate dynamics in two ways. On one side, the injection of the saline and warm Mediterranean Outflow Water (MOW) contributes to North Atlantic deep-water formation. In return, the Atlantic inflow is considered a sink of less saline water for the North Atlantic Ocean. However, while the history of MOW is the focus of numerous studies, the Pliocene Atlantic inflow has received little attention so far. The present study provides an assessment of the Mediterranean-Atlantic exchange with a focus on the Atlantic inflow strength and its response to regional and global climate from 3.33 to 2.60 Ma. This time interval comprises the mid-Pliocene warm period (MPWP; 3.29-2.97 Ma) and the onset of the Northern Hemisphere glaciation (NHG). For this purpose, gradients in surface δ 18 O records of the planktonic foraminifer Globigerinoides ruber between the Integrated Ocean Drilling Program (IODP) Hole U1389E (Gulf of Cádiz) and Ocean Drilling Program (ODP) Hole 978A (Alboran Sea) have been evaluated. Interglacial stages and warm glacials of the MPWP revealed steep and reversed (relative to the present) W-E δ 18 O gradients suggesting a weakening of MediterraneanAtlantic exchange likely caused by high levels of relative humidity in the Mediterranean region. In contrast, periods of stronger inflow are indicated by flat δ 18 O gradients due to more intense arid conditions during the severe glacial Marine Isotope Stage (MIS) M2 and the initiation of NHG (MIS G22, G14, G6-104). Intensified Mediterranean-Atlantic exchange in cold periods is linked to the occurrence of icerafted debris (IRD) at low latitudes and a weakening of the Atlantic Meridional Overturning Circulation (AMOC). Our results thus suggest the development of a negative feedback between AMOC and exchange rates at the Strait of Gibraltar in the latest Pliocene as it has been proposed for the late Quaternary.

Horizontal and Vertical Distribution of Perfluoroalkyl Acids (PFAAs) in the Water Column of the Atlantic Ocean

“…Previously, studies have concluded that the Atlantic Ocean is a source of contamination to the Mediterranean Sea or that there is no significant flow of PFAAs between the water bodies . These conclusions were based on comparisons of surface water measurements made in different studies in the Mediterranean Sea , and the Atlantic Ocean. ,, However, since outward transport of Mediterranean seawater into the Atlantic Ocean occurs at intermediate depth (500–1500 m) as well as at the surface, comparisons of surface water measurements alone are not suitable to determine the flux of PFAAs between the two water bodies.…”

Phenotypic strategies for Jasione L. or the challenge that taxonomy face to recent floristic responses along western Eurasia

“…Such community diversity would be decisive to guarantee its migrations under climatic changes: richness of herbaceous life forms (Tomiolo and Ward 2018), ability for propagule fast migrations (Matlack 1994), or because of their biological capacities to colonize alpine environments (Alexander et al 2015). In this sense, the genetic flux involved along such glacial-interglacial processes (García-Gallardo et al 2018;Suc et al 2018) caused remarkable changes in the vegetation.…”