The volcanic plume from the Eyjafjallajökull eruption has caused significant disruption to air transport across Europe. The regulatory response, ensuring aviation safety, depends on dispersion models. The accuracy of the dispersion predictions depend on the intensity of the eruption, on the model representation of the plume dynamics and the physical properties of the ash and gases in the plume. Better characterisation of these processes and properties will require improved understanding of the near-source plume region. This project will bring to bear observations and modelling in order to achieve more accurate and validated dispersion predictions. The investigation will seek to integrate the volcanological and atmospheric science methods in order to initiate a complete system model of the near-field atmospheric processes. This study will integrate new modelling and insights into the dynamics of the volcanic plume and its gravitational equilibration in the stratified atmosphere, effects of meteorological conditions, physical and chemical behaviour of ash particles and gases, physical and chemical in situ measurements, ground-based remote sensing and satellite remote sensing of the plume with very high resolution numerical computational modelling. When integrated with characterisations of the emissions themselves, the research will lead to enhanced predictive capability. The Eyjafjallajökull eruption has now paused. However, all three previous historical eruptions of Eyjafjallajökull were followed by eruptions of the much larger Katla volcano. At least two other volcanic systems in Iceland are 'primed' ready to erupt. This project will ensure that the science and organisational lessons learned from the April/May 2010 response to Eyjafjallajökull are translated fully into preparedness for a further eruption of any other volcano over the coming years. Overall, the project will (a) complete the analysis of atmospheric data from the April/May eruption, (b) prepare for future observations and forecasting and (c) make additional observations if there is another eruption during within the forthcoming few years.

The subpolar region of the North Atlantic is crucial for the global climate system. It is where coupled atmosphere-ocean processes, on a variety of spatial scales, require an integrated approach for their improved understanding and prediction. This region has enhanced 'communication' between the atmosphere and ocean. Here large surface fluxes of heat and moisture make the surface waters colder, saltier and denser resulting in a convective overturning that contributes to the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). The AMOC is an ocean circulation that carries warm water from the tropics northward with a return flow of cold water southwards at depth; it is instrumental in keeping Europe's climate relatively mild. The Iceland Sea - to the north and east of Iceland - is arguably the least studied of the North Atlantic's subpolar seas. However new discoveries are forcing a redesign of our conceptual model of the North Atlantic's ocean circulation which places the Iceland Sea at the heart of this system and suggests that it requires urgent scientific focus. The recently discovered North Icelandic Jet is thought to be one of two pathways for dense water to pass through the Denmark Strait - the stretch of ocean between Iceland and Greenland - which is the main route for dense waters from the north to enter the Atlantic. Its discovery suggests a new paradigm for where dense water entering the North Atlantic originates. However at present the source of the North Icelandic Jet remains unknown. It is hypothesized that relatively warm Atlantic-origin water is modified into denser water in the Iceland Sea, although it is unclear precisely where, when or how this happens. We will test this hypothesis and investigate this new ocean circulation paradigm. We will examine wintertime atmosphere-ocean processes in the Iceland Sea by characterising its atmospheric forcing, i.e. observing the spatial structure and variability of surface heat, moisture and momentum fluxes in the region and the weather systems that dictate these fluxes. We will make in situ observations of air-sea interaction processes from several platforms (an aircraft; and via project partners an unmanned airborne vehicle, a meteorological buoy and a research vessel) and use these to evaluate meteorological analyses and reanalyses from operational weather forecasting centres. These meteorological analyses and reanalyses are a blend of observations and model output and represent the atmosphere as best we know it. We will carry out numerical modelling experiments to investigate the dynamics of selected weather systems which strongly influence the region, but appear not to be well represented; for example, the boundary layers that develop over transitions between sea ice and the open ocean during cold-air outbreaks; or the jets and wakes that occur downstream of Iceland. We will use our unique observations to improve model representation of these systems. We will also carry out new high-resolution climate simulations. A series of experiments will cover recent past and likely future situations; as well as some idealised situations such as no wintertime sea ice in the Iceland Sea region. We will use a state-of-the-art atmospheric model with high resolution over the Iceland Sea to investigate changes in the atmospheric circulation and surface fluxes. Finally, in collaboration with our international partners, we will analyse new ocean observations and establish which weather systems are important for changing ocean properties in this region. We will use a range of ocean and atmospheric models to establish how current and future ocean circulation pathways function. In short, we will determine the role that atmosphere-ocean processes in the Iceland Sea play in creating the dense waters that flow through Denmark Strait and feed into the lower limb of the AMOC.

For the first time in the modern age we have the opportunity to study at first hand the environmental impact of a flood basalt (>1 km3 fissure eruption). Flood basalt eruptions are one of the most hazardous volcanic scenarios in Iceland and have had enormous societal and economic consequences across the northern hemisphere. A flood basalt eruption was included in the UK National Risk Register in 2012 as one of the highest priority risks. The Holuhraun eruption reached the flood basalt size sometime after 20 October 2014. It is now the largest flood basalt in Iceland since the Laki eruption in 1783-84, which caused the deaths of >20% of the Icelandic population by environmental pollution and famine and likely increased European levels of mortality through air pollution by sulfur-bearing gas and aerosol. The pollution from Holuhraun has been intensifying over the last few weeks, reaching a "Dangerous" level for the first time in Iceland on 26 October (as defined by the World Health Organisation). During 18-22 September, SO2 fluxes reached 45 kt/day, a rate of outgassing rarely observed during sustained eruptions, suggesting that the sulfur loading per kg of erupted magma (we estimate >0.35 wt%) exceeds both that of other recent eruptions in Iceland and perhaps also other historic basaltic eruptions globally, raising questions regarding the origin of these prodigious quantities of sulfur. A lack of data concerning conversion rates of SO2 gas into aerosol, the residence times of aerosol in the plume and the dependence of these on meteorological factors is limiting our confidence in the ability of atmospheric models to forecast gas and aerosol concentrations in the near- and far-field from Icelandic flood basalt eruptions. Preliminary study of the erupted products highlights two extraordinary features: (1) matrix glasses contain up to 1000 ppm sulfur (<100 ppm is expected for degassed melt) and are extremely heterogeneous and (2) abundant sulfide liquid globules in the matrix glass are "caught in the act" of breaking down on quenching, suggesting that sulfur is not only supplied by the melt, but also by the breakdown of sulfide liquid during degassing. These observations highlight a previously overlooked but potentially very large reservoir of sulfur that leaves little petrological record. These results might go some way towards understanding the extremely high sulfur yield of this eruption and have implications for assessing the environmental impact. This project combines the expertise of a large group of researchers to understand better the sulfur and chalcophile metal budget of the Holuhraun eruption. We will follow the formation of sulfide liquids, through to their breakdown on degassing, to the outgassing of SO2 gas and conversion to aerosol. The entire pathway is not well understood, particularly given complexities related to the rapid magma ascent rates postulated for the Holuhraun magmas and the lack of ash in the plume, both of which we hypothesise impose kinetic constraints on sulfur processing in different parts of the system. We will carry out detailed petrological, geochemical measurements of lavas and plume chemistry to understand the sulfur budget and to feed into models of plume chemistry and dispersion, which are essential for hazard monitoring.

The Fagradalsfjall eruption in Iceland began on 19th March 2021 and until the 27th of April was characterised by low-altitude continuous degassing of mainly sulfur dioxide. On 27th April, the nature of the eruption changed to continuous lava fountaining, then changed again on 2nd May from continuous to pulsed fountains up to 300m high with a doubled lava discharge rate. Since 27th April, long-range transport of the volcanic plume off the coast of Iceland has occurred and satellite imagery shows that the eruption has been influencing clouds in the North Atlantic. The eruption presents a rare opportunity to make the first ever aircraft measurements of cloud properties perturbed by volcanic activity. Volcanic eruptions that emit gases such as sulfur dioxide into the lowermost part of our atmosphere have been recognised in the last decade as a perfect natural lab to study how emissions affect cloud amount and the physical properties of clouds, which includes the size of the tiny droplets that make up clouds. Clouds have a net cooling effect on climate because they reflect some of the incoming sunlight back to space. It is also known that emissions of gases such as sulfur dioxide (be they man-made or natural) cause changes to cloud properties once the gas-phase species are converted to airborne particles, but the details of the interplay of clouds, particles and the amount of sunlight reflected back to space are extremely complex and challenging to represent in climate models despite decades of research efforts. This project would deliver the very first measurements of cloud characteristics including changes in the vertical in areas that have been affected by the volcanic emissions. This can then be contrasted to areas that have not been affected by volcanic emissions. When combined with satellite data, our dataset will enable a new understanding of cloud and aerosol particle interactions, which in turn will help to improve model representation of these climate-relevant processes. Better models will provide a more accurate estimate of climate change, which will help to better prepare and mitigate climate change hazards.

Weather-driven hazards, such as floods, storms, landslides and severe winter weather, account for 90% of the world's natural disasters, causing significant impacts to people, infrastructure and natural environments. Across Northern Europe, these hazards are becoming more pervasive in a changing climate. As they do, and as other 'emergent' hazards, such as wildfires and droughts, start to affect parts of Northern Europe where they have not before, transport links and supply chains, ecosystems, agricultural yields and forestry are increasingly being impacted. These impacts are intrinsically linked to resilience and coping capacities, with their severity greatest in the most vulnerable and remote regions, including people, economies and communities, the infrastructure that supports and connects them, and the goods and services they produce. Recent floods and landslides in remote regions across Northern Europe have been related to the same weather systems, however our understanding of the timing and impacts from these interconnected events is poorly understood, highlighting a critical need to better understand, and find novel solutions to, the emerging risks of weather-driven natural hazards in remote regions. The EMERGE project, formed by a new multi-hazard focused international partnership between the University of Strathclyde, the Icelandic Meteorological Office, and the Norwegian Water Resources and Energy Directorate, in collaboration with British Geological Society, Newcastle University, and the Scottish Environment Protection Agency, brings together experts to explore weather-driven hazards - primarily extreme rainfall, landslides and floods - and their emergent and compounding risks across Northern Europe's remote and vulnerable regions. EMERGE has a focus of the UK, Norway and Iceland, aimed at bringing together researchers that work in similar climatic zones to foster collaboration and create novel, cutting-edge science that is beneficial to both the UK and its near neighbours. EMERGE's activities will address critical research questions relating to: (1) the emergence and compounding risks of weather-driven natural hazards in remote regions; (2) the observation, prediction and monitoring of these hazards across the UK, Iceland and Norway; and (3) regional research priorities and resilience-building strategies. These will be explored through a series of expert workshops and 'living labs' in Glasgow, Oslo and Reykjavik, supported by wider dissemination activities, that will create a forum that fosters open scientific collaboration, knowledge brokering and information sharing, and identifies needs and opportunities. Our remote communities and environments must undergo significant change if they are to successfully transition to being climate resilient. The grand challenge presented by climate change, combined with the disproportionate impacts of natural hazards in remote regions, demands a new international approach to society's interaction with the environment in order to build a more equitable and sustainable future. The new partnerships formed by EMERGE will develop world-leading research to produce critical new scientific knowledge and support the development of solutions that build climate resilience in some of our most vulnerable regions.