Dissolved gases in the deep North Atlantic track ocean ventilation processes

Area of Science:

• Oceanography
• Geochemistry
• Climate Science

Background:

• Gas exchange between atmosphere and ocean is crucial for global climate and biogeochemistry.
• Direct observations of these processes are limited, hindering understanding of physical mechanisms.
• Dissolved noble gases and their isotopes are valuable, yet underexplored, tracers of air-sea interactions.

Purpose of the Study:

• To evaluate gas exchange parameterizations using high-precision noble gas isotope and elemental ratio data.
• To investigate the role of deep convection and bubble-mediated gas exchange in the North Atlantic.
• To distinguish physical from biogeochemical signals in deep-ocean gas concentrations.

Main Methods:

• Collected high-precision noble gas isotope and elemental ratio data from the deep North Atlantic.
• Utilized an ocean circulation model to evaluate gas exchange parameterizations.
• Compared dissolved N2/Ar measurements with physics-only model predictions.

Main Results:

• Revealed deep-ocean undersaturation of heavy noble gases and isotopes due to cooling-driven air-to-sea transport.
• Indicated a substantial role for bubble-mediated gas exchange in transferring sparingly soluble gases.
• Identified excess N2 in deep North Atlantic waters, suggesting significant benthic denitrification.

Conclusions:

• Noble gas data provide critical validation for ocean circulation models and air-sea gas exchange processes.
• Deep convection in high latitudes significantly impacts noble gas distribution.
• Nitrogen removal rates in the deep Northeastern Atlantic are at least three times the global average, implying strong coupling with carbon export.