Abrupt climate shift in the Western Mediterranean Sea

Area of Science:

• Oceanography
• Climate Science
• Marine Biology

Background:

• Oceanographic measurements over a century show gradual increases in Mediterranean water temperature and salinity.
• Vertical stratification of water masses remained largely unchanged until 2005.

Purpose of the Study:

• To report evidence of reinforced thermohaline variability in the deep western Mediterranean basin.
• To detail the chronological order of abrupt structural changes in intermediate and deep water layers starting in 2005.
• To track the route of newly formed water masses and assess their impact on the North Atlantic and Mediterranean ecosystems.

Main Methods:

• Analysis of long-term oceanographic measurement data.
• Identification and characterization of dense water formation events.
• Tracking the dispersal of new water masses within the Mediterranean and towards the Atlantic.

Main Results:

• Significant dense water formation events occurred, producing warmer, saltier, and denser water masses than previously recorded.
• Abrupt changes in the structure of intermediate and deep water layers were observed starting in 2005.
• New deep waters are flowing eastwards and towards the Atlantic Ocean via the Strait of Gibraltar.

Conclusions:

• The Mediterranean deep basin is experiencing reinforced thermohaline variability, indicating a climate shift.
• Outflowing deep waters will impact the North Atlantic's heat and salt content.
• Modifications in Mediterranean abyssal ecosystems and biogeochemical cycles are anticipated.