Pathways and Emissions of climate-relevant TRace gases in a changing Arctic Ocean (PETRA)

The Arctic Ocean is exceptionally susceptible to climate change. Recent studies have shown that surface seawater is warming faster than in other oceans. In addition, atmospheric CO2 dissolution in seawater is causing Ocean Acidification (OA). The documented retreat of sea-ice will increase light penetration, including UV. These environmental parameters (temperature, OA and UV) are highly likely to act as stressors and alter the Arctic Ocean ecosystem structure and function which in turn will feed back on climate. One such feedback is the cycling of climatically active trace gases and their emission to the atmosphere (here: CH4, N2O, DMS, CO). These trace gases are rapidly produced and consumed by a number of physical and biological processes. For example, the biggest source of CO in surface seawater is via UV-induced photochemical reactions. Yet, the likely response of trace gas cycling to climate change remains largely unexplored. This hinders our ability to predict the future direction of this important climate-feedback. We propose to investigate this feedback by a) developing the basic understanding which will underpin a predictive tool and b) developing the predictive tool itself (computer model). We will achieve this using three complimentary tools:
Firstly, novel, high-tech spatial observations of trace gases (with depth as well as horizontal) which will allow us to identify major controls on their cycles and estimate their present flux to the atmosphere.
Secondly, direct experiments where the three stressors will be manipulated while trace gas cycling pathways are monitored. The novelty of our approach here, lies in the use of individual and combined stressor manipulation (e.g. OA alone versus high temperature and OA together). This will allow us to explore potential synergistic or antagonistic effects between stressors. We will use state-of-the-art chemical and biological observations to track changes in trace gas cycling. For example, we will monitor the abundance and activity of key genes involved in trace gas cycling. These experiments will give us explicit and refined understanding of trace gas cycling in relation to the stressors.
Thirdly, we will employ computer modelling which will translate this understanding into a predictive tool that will be used to predict the impact of future climate change.
Finally, and in order to rapidly translate our relevant findings to policy, we will engage with the public, policymakers, international science programmes and Intergovernmental Panel on Climate Change (IPCC) through our comprehensive impact plan.

Who and How? The main beneficiaries outside of the scientific community for our project are:
The media and the public: PETRA researchers are very involved in promoting a good public understanding of science, particularly ocean acidification and the impact of climate change on the carbon cycle. The work of PETRA will serve as a basis for supporting active discussions on what to do about climate change, and how the earth and particularly the Arctic Ocean is responding to it. Through our involvement with LikeToBe.org and PETRA sponsorship of schools involvement we will engage directly with key stage 3 to 5 students, and will produce web-based material for teaching purposes. This will be directed to communicate the expeditionary and state of the art nature of this project, to instil the excitement of discovery based science, whilst providing a unique learning experience with respect to the significance of climate change to marine ecosystems.

Policymakers: National and international policymakers will benefit from results of PETRA to inform policy on climate change. PETRA will provide information on the Arctic contribution to cumulative trace gases. This information is relevant to determine what CO2 emissions pathways are realistic for given climate targets, and the risks associated with these pathways.

The IPCC,UNFCCC and Arctic Council: PETRA will provide key information on the anthropogenic influence on oceanic fluxes of climatically active, including greenhouse gases (N2O, CH4, CO) (1) over the historical period informing the understanding of trace gas balance that the IPCC tries to achieve, and (2) projected for various levels of CO2 and climate change, informing the cumulative CO2-equivalent budget associated with climate targets. This will contribute to decision making associated with the implementation of the Paris Agreement on climate change, by helping to assess which climate target is achievable and how, and what is the difference between various levels of climate change which will influence the revisions of Nationally Determined Contributions.