SIMbRICS: Sea Ice Microbiology and the Role In Cycling of Sulfur (DMS, DMSP, DMSO, MT)

The Arctic Ocean is undergoing unprecedented changes as the Earth warms due to climate change. Increasing global temperatures are resulting in increased rates of glacial melting and retreat, thawing of the permafrost and a steady trend towards reduced sea ice extent in winter. Inputs of freshwater into the Arctic Ocean are also increasing as a result of the increased melting rates. As the sea ice retreats, the reflective surface of the ice is replaced by absorptive 'dark' ocean, and results in a greater absorption of incoming sunlight and heat energy, thus driving up the rate of global temperature increase. However, this picture is too simplistic, and there are many physical and biological processes taking place within the Arctic Ocean water and sea ice which we do not fully understand, but which could affect our projections of changes within the Arctic Ocean.

In Autumn 2019, the German Icebreaker FS Polarstern is undertaking a unique expedition, to sail to the edge of the Arctic sea ice in the Russian Laptev Sea, and allow the sea ice to form around the ship. The ship will then drift with the ice pack, close to the North Pole, and exit the sea ice in Autumn 2020 near the east coast of Greenland. This opportunity will allow scientists access to newly formed 'first year' sea ice, as well as older 'multi-year' ice, and allow them to study all aspects of the Arctic environment across an entire year and all the seasonal changes: physical interactions between atmosphere, sea ice and water column, and the biological activities taking place in all three environments. It is essential we work towards gathering this information now, as it will allow us much better understanding of the processes taking place, and allow us to improve our model predictions of how the Arctic will change over the coming decades.

This project has been designed as a key part of this expedition, and will study the formation of a gas called dimethylsulfide (DMS), a key ingredient in the cocktail of gases that makes up the 'smell of the sea'. It is produced worldwide by single celled algae and bacteria in both freshwater and saltwater environments, but our previous research has shown that sea-ice-dwelling algae produce concentrations of DMS tens to hundreds of times higher than in the water. While only a small proportion (up to 16%) of this DMS is released into the atmosphere, once there it forms cloud-seeding compounds which can influence our weather and climate. When it rains, sulfur compounds are deposited back into the soils of our continents. The remainder of the DMS formed in the oceans stays there, facing consumption by marine microbes and incorporation into the oceanic sulfur cycle. As we know that sea ice is an important source of DMS, the reduction in sea-ice extent with increasing climate change will have significant effects on the volume of DMS entering the atmosphere.

Our project aims to investigate the changes in the microbial (bacterial and algal) community across the seasonal changes in the Arctic, and to look at how these changes affect the production rates of DMS and associated organic sulfur compounds. To this end, we will undertake 2 months stationed on FS Polarstern during the boreal spring, and form international collaborations to extend our sample availability to over 6 months through spring to summer. We will continue our research in the home laboratory by studying so-called 'model micro-organisms' which we will collect during our time at sea (or in the ice!). All our data collected in the Arctic will be compared to our previous studies in the Antarctic, to give a much clearer picture of the importance of the polar regions as a source of DMS, and how climate change will affect our global climate as these areas change.

This project will provide critical information for the processes controlling sulfur cycling in the Arctic Ocean, and will link in situ concentrations and production and loss rates alongside molecular biological studies of the microbial community for the first time, and to extend this over an annual cycle. As part of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), this project will be a major contributor to the first year-round expedition to explore the Arctic climate system as part of a major international collaboration, and a baseline for understanding the changes which will take place in the Arctic Ecosystem as climate change progresses. As such, the impacts of this fundamental research will be relevant for a number of different audiences including marine scientists, microbiologists, modellers, atmospheric and climate scientists, policy makers, as well as the general public.

Academic audiences will benefit from this research through better understanding of production and loss processes for sulfur compounds within the Arctic sea ice and water column. The Polar Regions are experiencing particularly strong climate change, and at the same time are hot spots for DMS cycling, and the potential feedbacks of altered atmospheric DMS fluxes for regional climate control are particularly high, and an essential component for modelling regional and global future climate change. The planned work on sulfur cycling in the Arctic will enhance the existing limited literature on DMS production from the sea ice zone. Many processes in the Arctic climate system are poorly represented in climate models because they are not sufficiently understood: climate scientists will benefit from the new knowledge gained that will be incorporated into models with an increased capability to better predict DMS concentrations in seawater and sea ice, and the resulting emissions to the atmosphere. Beneficiaries include organizations such as the Intergovernmental Panel for Climate Change (IPCC).

Policy makers will benefit from the research through the improved capabilities of future climate modelling based on the insights from the research as described above. Climate change is undoubtedly the biggest and most important challenge faced by humanity and policy needs to be formulated and enacted in order to avoid dangerous levels of climate change to occur. Through improving climate forecasting, our research will contribute to the knowledge base on which policy makers can make informed decisions that will steer the direction of the UK, European and global economic and environmental strategies for the next decades.

The general public will benefit from this research through better informed environmental policy (above) and better climate predictions. It is essential to communicate the outcomes of complex environmental processes to the public in order to generate a better overall public understanding of science. MOSAiC has a detailed outreach plan in place for dissemination of information throughout the year-long drift, and beyond, to include video documentaries for TV broadcast, blogs, press releases and detailed stories. We plan to incorporate our outreach activities within this core media pool, as well as use a wide variety of methods to engage with general public end-users, including a detailed project website (for example www.dimethylsulfide.org), regular updates by social media such as the Twitter accounts of institutions and investigators involved (e.g @WarwickLifeSci, @HSchafer_lab, @Chen_group, @DutchDMS), publications in popular magazines (e.g. Microbiology Today, Planet Earth, the Conversation), as well as presentations to the public through presentations during Open Days and public science events.