Methyl bromide cycling in a warm‐core eddy of the North Atlantic Ocean

• Published in: Global Biogeochemical Cycles
• Main Authors: Yvon‐Lewis, Shari A, Butler, James H, Saltzman, Eric S, Matrai, Patricia A, King, Daniel B, Tokarczyk, Ryszard, Moore, Robert M, Zhang, Jia‐Zhong
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: eScholarship, University of California 2002
• Subjects: methyl bromide; degradation; production; air/sea flux; vertical mixing; Atmospheric Sciences; Geochemistry; Oceanography; Meteorology & Atmospheric Sciences; North Atlantic
• Online Access: https://escholarship.org/uc/item/8928t6hs; https://escholarship.org/content/qt8928t6hs/qt8928t6hs.pdf; https://doi.org/10.1029/2002gb001898

We conducted a detailed investigation of the evolution of methyl bromide concentrations, degradation rates, and ventilation rates for 26 days in a naturally contained, warm-core eddy of the North Atlantic Ocean. This is the first study of the oceanic cycling of methyl bromide in a natural, contained system with a complete suite of supporting measurements of physical and chemical variables. Methyl bromide concentrations in the mixed layer ranged from 2.3 to 4.2 nmol m-3, degradation rates ranged from 0.1 to 0.9 nmol m-3 d-1, net sea-to-air exchange rates ranged from 0 to 0.5 nmol m-3 d-1, and net loss rates through the thermocline were less than 0.1 nmol m-3 d-1. From a mass balance for methyl bromide in the mixed layer, we calculated production rates ranging from <0.1 to 1.3 nmol m-3 d-1. The median of this range, 0.48 nmol m-3 d-1, is higher than the ∼0.15 nmol m-3 d-1 necessary to maintain the reported global oceanic emission of 56 Gg yr-1. This is reasonable, because our study area was supersaturated in methyl bromide, whereas the ocean as a whole is undersaturated.