Directly measured mid-depth circulation in the northeastern North Atlantic Ocean.

Area of Science:

• Oceanography
• Climate Science
• Geophysics

Background:

• Ocean circulation, particularly heat transport, is crucial for global climate regulation.
• Satellite observations are limited to surface waters, leaving deep ocean currents under-measured.
• Accurate measurements of deep ocean circulation are essential for climate modeling.

Purpose of the Study:

• To quantify absolute velocities of water masses at two distinct depths in the northeastern North Atlantic.
• To investigate the pathways and extent of warm water transport from subtropical regions and the Mediterranean Sea.
• To determine the influence of seafloor topography on deep ocean current patterns.

Main Methods:

• Deployment of acoustically tracked floats for comprehensive, direct observation of deep ocean currents.
• Quantitative mapping of absolute velocities at approximately 600 m depth (thermocline) and another deeper level.
• Analysis of current pathways in relation to the Mid-Atlantic Ridge and its topographical features.

Main Results:

• The majority of northward heat transport via the Gulf Stream system stays within the subpolar region, with limited entry into the Rockall trough or Nordic seas.
• Warm, saline Mediterranean outflow reaches high latitudes through narrow slope currents and mixing, challenging previous assumptions.
• Ocean currents consistently cross the Mid-Atlantic Ridge at deep gaps, indicating topographical control on circulation.

Conclusions:

• Deep ocean circulation patterns are significantly influenced by seafloor topography, particularly at the Mid-Atlantic Ridge.
• Understanding these deep currents is vital for accurate climate change predictions and oceanographic models.
• The transport mechanisms of warm, saline waters to high latitudes have been refined by this study.