Nitrogen-containing compounds, including glycine betaine (GBT), choline and trimethylamine N-oxide (TMAO) are ubiquitous in marine organisms. They are used by marine organisms as compatible solutes in response to changes in environmental conditions, such as increasing salinity, because they do not interfere with cell metabolism. They also have beneficial effects in protecting proteins against denaturation due to chemical or physical damage. In the marine environment, these compounds are frequently released from these organisms directly into seawater due to changing environmental conditions, such as by viral lysis or grazing. The released nitrogenous osmolytes serve as important nutrients for marine microorganisms, which can use them as carbon, nitrogen and energy sources. It is well known that the degradation of these nitrogenous osmolytes contribute to the release of climate-active gases, including volatile methylamines. Methylamines are important sources of aerosols in the marine atmosphere, which help to reflect sunlight and cause a cooling effect on the climate. Our NERC-funded research is starting to understand the microbial metabolism of these compounds and their seasonal cycles in the coastal surface seawater, but our understanding across the world's oceans is limited. Of particular importance to the Earth's climate is the Southern Ocean. The Southern Ocean is an important player in the Earth climate system, and is an ideal region to study ocean-atmosphere connections because of its isolation from continental emissions and the strong circumpolar atmospheric circulation, rendering its air pristine. Opportunities to study the Southern Ocean are rare however, and it remains under sampled even for the most routine measurements compared to the rest of the World's oceans. We have a unique opportunity within the Antarctic Circumnavigation Expedition (ACE) to make measurements and collect samples around the entire Southern Ocean, and near Antarctica. Twenty one other international projects will also be conducting research from the same expedition, and six of these projects have excellent links to our research. Unfortunately, there are no plans for after the expedition for the projects to collaborate and integrate data, which is a real missed opportunity. This proposal aims to develop a new international network with six ACE projects and use post-cruise activities to exploit data and knowledge generated to capitalise on our NERC-funded research on nitrogenous osmolytes and to increase its international breadth.