Theme 3: Atmospheric deposition and ocean biogeochemistry

Focus on key regions where atmospheric depositions and their impacts are important to marine primary production and biogeochemistry. These regions include the Mediterranean Sea, the Southern Ocean, the Tropical Atlantic, and the North Pacific.

Encourage the setup and maintenance of time series sampling stations (over the ocean, on islands, and/or in coastal areas) to monitor and accurately estimate atmospheric depositions and fluxes (vertical and horizontal) of bio-available nutrients to the marine environment.

Support comparative studies on the budgets of bio-available nutrients in the surface waters of the key regions mentioned above in order to address the role of atmospheric deposition, particularly in nitrate-, phosphate- and iron-limited regions. With these comparative studies, regional coupled modelling can address both the atmosphere and the ocean.

Use new and improved tools to effectively study the impacts of atmospheric deposition on ocean biogeochemistry, such as isotope tracers and molecular biology techniques (genomics, transcriptomics, and proteomics). Also, new remote sensing platforms have become available in the recent years and may provide significant advances. Specifically, the new network of Geostationary satellites (GOES 16/17, Himawari 8/9, GOCI, and others) make observations of the ocean basins every 10 minutes (day and night). A much better understanding of aerosol transport evolution and deposition will be gained through these new tools. While only one of them has dedicated channels for ocean observations (GOCI), its observing region is the North Pacific, a key of interest for aerosol-ocean interactions. An improved understanding of wet deposition over the ocean by precipitation is expected with the new merged data base of senior and newest measurements from the constellation of satellites in the Global Precipitation Mission (GPM) into the Integrated Multi-satellitE Retrievals for GPM (IMERG; https://gpm.nasa.gov/gpm/imerg-global-image) with a half hour frequency and 6 hr latency.

AMBIEnCE: https://projectambience.wordpress.com/
Tudor Hill: http://www.bios.edu/research/projects/tudor-hill-marine-atmospheric-observatory/

Because of the overlapping nature of many SOLAS and GEOTRACES activities, closer interactions between the two organizations are being pursued, particularly in the area of atmospheric and water column sampling, where each program has different strategies and different overall goals. A first attempt to bring the two communities together towards coordinating common goals and protocols resulted in a recent publication (Meshkidze et al., 2020, Perspective on identifying and characterizing the processes controlling iron speciation and residence time at the atmosphere-ocean interface, https://doi.org/10.1016/j.marchem.2019.103704).

Given the recent discovery of dust deposition in the NE Pacific from North American sources and the large volume of research output from the East Asian community on the subject of aerosol deposition, the team leaders recommend investigating whether there is US and Asian interest for a joint study focusing on aerosol transport and deposition in the North Pacific. The team leaders will contact individual key scientists on both sides of the Pacific and evaluate if there is interest for a coordinated initiative. The topic session “Atmospheric nutrient deposition and microbial community responses, and predictions for the future in the North Pacific Ocean” was accepted for the PICES-2020 and -2021 annual meetings.