A new study by PML scientists has been published in Proceedings of the National Academy of Sciences (PNAS) describing the first direct measurement of air-sea methanol exchange over the open ocean, along a north-south transect of the Atlantic.
In the surface ocean, methanol is rapidly consumed by marine microbes as a source of carbon and energy. There are many sources of methanol in the atmosphere, including emissions from trees and gases, fossil fuel combustion and industrial fuel use. Methanol is the second most abundant organic gas in the atmosphere and affects the atmospheric chemistry. It is also indirectly linked to climate because the abundance of methanol affects the concentration of the hydroxyl radical – a natural ‘cleansing agent’ of the atmosphere that removes many pollutants in the air (including the major greenhouse gas methane).
Transport of gases between the ocean and the atmosphere, known as ‘air-sea gas exchange’, has profound implications for our environment and the Earth’s climate. The main goal of this study was to understand of how much, and in which direction, methanol is being transferred between the atmosphere and the ocean. The study also utilised methanol as a ‘proxy gas’ with which to study the general physical processes involved in air-sea gas exchange. The rate of transfer of soluble organic compounds like methanol is currently poorly understood, largely due to a scarcity of open-ocean measurements.
The research estimated the global oceanic uptake of methanol and examined the lifespan of this compound in the lower atmosphere and the upper-ocean with respect to gas exchange. It also quantified the rate of methanol deposition and examined the governing processes near the air-sea interface. The study improves our overall understanding of the roles organic compounds play in the atmosphere as well as ocean.