Atmospheric deposition of trace elements and nutrients to the ocean can significantly modify seawater chemistry and influence oceanic productivity.  However, mounting evidence suggests that the response of phytoplankton to atmospheric deposition depends on the chemical composition of the aerosols and varies across different phytoplankton species.  Responses are also different depending on oceanographic setting and season. To determine if and how nutrients, metals and other constituents from atmospheric deposition influence plankton activity and community structure in the ocean we analysed nutrient and metal concentrations in marine aerosols and tested how these constituents impact phytoplankton.  This is done using incubation experiments with natural phytoplankton assemblages and different sources and amounts of aerosol or pure nutrients and metal additions.  Variance in utilization of nutrients and susceptibility to metal toxicity was identified among different taxa, suggesting that aerosol deposition could potentially alter patterns of marine primary production and phytoplankton community structure.  In addition, input of bioaerosols can also affect phytoplankton communities and should be considered. Importantly, up to 25% of airborne microbes are viable upon deposition and may compete for resources with marine organisms. Airborne viruses can also infect specific phytoplankton hosts and hence impact the ecosystem. Natural and anthropogenic change could impact the chemical and biological composition of aerosols with consequences to ocean chemistry and productivity with potential feedbacks to the carbon cycle.

How to cite: Paytan, A.: Atmospheric Deposotion Impacts on Marine Biogeochemistry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-902, https://doi.org/10.5194/egusphere-egu22-902, 2022.

To fulfill the international objective “…to reach global peaking of greenhouse gas emissions as soon as possible … and to undertake rapid reductions thereafter in accordance with best available science...to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century”, the Paris Agreement implemented the Global Stocktake Process to assess regularly the world’s collective progress towards achieving the purpose of the agreement and its long-term goals.

National greenhouse gas (GHG) inventories report only anthropogenic fluxes. However, many GHG sources are difficult to separate from the natural fluxes. Moreover, inventories cannot easily be scaled to the globe given the use of different approaches for GHG budgeting but, more importantly, because the states of the natural ocean and land sinks are not considered. Fast developments in the scientific capabilities to quantify GHG budgets and their trends consistently from the global to the national scale as well as accurate attribution of budgets to natural and anthropogenic processes are needed.

In Global Carbon Budgets top-down and bottom-up estimates still show large discrepancies at regional or country scale, due to large and multiple sources of uncertainty. Reducing these uncertainties and improving regional GHG budgets is currently the focus of the second “REgional Carbon Cycle Assessment and Processes” (RECCAP-2) initiative supported by the Global Carbon Project. This effort is fueled by an ever-expanding constellation of and in-situ and satellite-based GHG observations, and by increased process-based and data-driven modelling capabilities.

Here, I will discuss some of the elements that still challenge our ability to robustly link global to the regional and country carbon budgets, and their implications for the Global Stocktake. I will then show recent examples on how multi data-stream approaches can be used to identify and understand sources of discrepancies between top-down and bottom-up estimates and to improve attribution of regional carbon budgets to specific natural and anthropogenic processes.  

How to cite: Bastos, A.: Carbon budgets from global to regional scales: current challenges and future perspectives, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3435, https://doi.org/10.5194/egusphere-egu22-3435, 2022.