Advances in understanding of air–sea exchange and cycling of greenhouse gases in the upper ocean

Abstract

The air–sea exchange and oceanic cycling of greenhouse gases (GHG), including carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), carbon monoxide (CO), and nitrogen oxides (NOx = NO + NO2), are fundamental in controlling the evolution of the Earth’s atmospheric chemistry and climate. Significant advances have been made over the last 10 years in understanding, instrumentation and methods, as well as deciphering the production and consumption pathways of GHG in the upper ocean (including the surface and subsurface ocean down to approximately 1000 m). The global ocean under current conditions is now well established as a major sink for CO2, a major source for N2O and a minor source for both CH4 and CO. The importance of the ocean as a sink or source of NOx is largely unknown so far. There are still considerable uncertainties about the processes and their major drivers controlling the distributions of N2O, CH4, CO, and NOx in the upper ocean. Without having a fundamental understanding of oceanic GHG production and consumption pathways, our knowledge about the effects of ongoing major oceanic changes—warming, acidification, deoxygenation, and eutrophication—on the oceanic cycling and air–sea exchange of GHG remains rudimentary at best. We suggest that only through a comprehensive, coordinated, and interdisciplinary approach that includes data collection by global observation networks as well as joint process studies can the necessary data be generated to (1) identify the relevant microbial and phytoplankton communities, (2) quantify the rates of ocean GHG production and consumption pathways, (3) comprehend their major drivers, and (4) decipher economic and cultural implications of mitigation solutions.

Simultaneous determination of seawater trimethylamine and methanol by purge and trap gas chromatography using dual nitrogen-phosphorus detector and flame-ionization detector

“…One carbon (C1) compounds, defined as molecules with no carbon-carbon bond, such as methane, methanol, methyl sulfides and methyl amines, are widespread on earth and play key roles in atmospheric chemistry and global warming (Yang et al, 2013;Masson-Delmotte et al, 2018;Sun et al, 2019;Mao et al, 2022;Hopkins et al, 2023;Bange et al, 2024). While methane and dimethyl sulfide have been intensively studied due to their impact on climate change (Charlson et al, 1987;Dean et al, 2018;Zhuang et al, 2018a;Forster et al, 2021;Mao et al, 2021), little is known about the biogeochemical cycling of other C1 compounds, such as trimethylamine and methanol (Van Neste et al, 1987;King, 1988;Singh et al, 2001;Zhuang et al, 2019;Fitzsimons et al, 2023).…”