The effect of submarine CO₂ vents on seawater Implications for detection of subsea carbon sequestration leakage

• Published in: Limnology and oceanography Vol. 60; no. 2; pp. 402 - 410
• Main Authors: Botnen, Helle Augdal, Omar, Abdirahman M., Thorseth, Ingunn, Johannessen, Truls, Alendal, Guttorm
• Format: Journal Article
• Language: English
• Published: John Wiley and Sons, Inc 01.03.2015
• ISSN: 0024-3590; 1939-5590
• DOI: 10.1002/lno.10037

The effect of submarine carbon dioxide (CO₂) vents on seawater carbonate chemistry have been determined using hydrographical and marine carbonate data obtained from two submarine hydrothermal vent fields, as well as a reference station, all near the Jan Mayen Island in the Norwegian-Greenland Sea. We have shown that one can successfully determine the excess carbon that enters the seawater from the vents by applying a modified version of a back-calculation technique, which is traditionally used to study the invasion of excess atmospheric CO₂ in the surface ocean. As a result of this excess carbon, total dissolved inorganic carbon (C T) in the seawater surrounding the vents was on average 12 μmol kg−1 (1-30 μmol kg−1) higher compared to samples obtained from a reference station outside the venting areas. The observed excess C T was most significant between 100 m and 200 m but was noticeable in all depths with the exception of the upper 10-20 m. The absence of a venting CO₂ signal in the surface water and the realism of the results are discussed. We believe the present method is promising for monitoring (detection and quantification) of CO₂ leakage into the water column due to its high sensitivity and readiness for automation.