The Effect of the Source of Deep Water in the Eastern Mediterranean on Western Mediterranean Intermediate and Deep Water

Yael Amitai,Yosef Ashkenazy,Hezi Gildor

doi:10.3389/fmars.2020.615975

Abstract

The deep water in the western Mediterranean Sea was found to be significantly affected by a climatic event that took place in the eastern Mediterranean during the 1990s. Numerical simulations of the entire Mediterranean Sea showed that multiple equilibria states in the eastern Mediterranean can exist under present-day-like conditions. The two stable states that were found are associated with intermediate water exchange between the eastern Mediterranean's Aegean and Adriatic Basins. In the first state, the Adriatic acts as a source of deep water that flows into the deep layers of the eastern Mediterranean; in the second state, there is no source of deep water in the Adriatic and the eastern Mediterranean intermediate water is warmer and saltier. We studied the water pathways, in both stable states, into the western Mediterranean and found that the eastern Mediterranean water's properties signature can be seen as far as the Gulf of Lion, which is an important open-ocean deep water convection site. Meaning that, the eastern Mediterranean water characteristics are manifested in deep and intermediate water properties all over the Mediterranean Sea. The water propagating from the eastern to the western Mediterranean also has different flow regimes, in both states, through the Sicily Strait and in the Tyrrhenian Basin, as seen from a Lagrangian analysis.

Highlights

The western Mediterranean Sea, from which warm and saline water flows to the Atlantic Ocean, has experienced substantial changes over the last decades
Deep water of the western Mediterranean Sea origin in open ocean convection events that take place in the Gulf of Lion area (Medoc Group et al, 1970). These were attributed to strong Mistral wind events (Cacho et al, 2000; López-Jurado et al, 2005; Font et al, 2007; Somot et al, 2018), and to the characteristics of water masses advected from the eastern Mediterranean into the western Mediterranean (Gasparini et al, 2005; Schroeder et al, 2006)
The difference between both states at the intermediate depth of 250 m (Figure 2) shows that there is a substantial influence of the Adriatic deep water formation (DWF) on the Adriatic itself and on the western Mediterranean’s Tyrrhenian Basin

Summary

Introduction

The western Mediterranean Sea, from which warm and saline water flows to the Atlantic Ocean, has experienced substantial changes over the last decades. Deep water of the western Mediterranean Sea origin in open ocean convection events that take place in the Gulf of Lion area (Medoc Group et al, 1970). These were attributed to strong Mistral wind events (Cacho et al, 2000; López-Jurado et al, 2005; Font et al, 2007; Somot et al, 2018), and to the characteristics of water masses advected from the eastern Mediterranean into the western Mediterranean (Gasparini et al, 2005; Schroeder et al, 2006). The western Mediterranean convection events were associated with the warm, saline Levantine Intermediate Water (LIW), which crossed the Sicily. Numerous studies demonstrated that the properties of LIW vary over different time scales (Mauri et al, 2019; Ozer et al, 2020). Wu and Haines (1996) modeled the LIW pathways in the Mediterranean and showed that the LIW’s salt content dictates the depth of convection in the GoL—namely, the saltier it is, the deeper it gets

Methods

Results

Conclusion