The Arctic region is undergoing dramatic changes, in the atmosphere, ocean, ice and on land. The Arctic lower atmosphere is warming at more than twice the rate of the global average, the Arctic sea ice and Greenland Ice Sheet melt have accelerated in the past 30 years. Notable observed changes in the ocean include the freshening of the Beaufort Gyre, and 'Atlantification' of the Barents Sea and of the Eastern Arctic Ocean. Such profound environmental change is likely to have implications across the globe - it is often said, "What happens in the Arctic doesn't stay in the Arctic". Past work has indicated that Arctic amplification can, in principle, affect European climate and extreme weather, but a clear picture of how and why is currently lacking. The 2019 Intergovernmental Panel on Climate Change (IPCC) Special Report on Oceans and Cryosphere concluded "changes in Arctic sea ice have the potential to influence midlatitude weather, but there is low confidence in the detection of this influence for specific weather types". ArctiCONNECT brings together experts in climate dynamics, polar and subpolar oceanography, and extreme weather, in order to transform understanding of the effects of accelerating Arctic warming on European climate and extreme weather, through an innovative and integrative program of research bridging theory, models of varying complexity, and observations. It will (i) uncover the atmospheric and oceanic mechanisms of Arctic influence on Europe; (ii) determine the ability of state-of-the-art climate models to simulate realistic Arctic-to-Europe teleconnections; and (iii) quantify and understand the contribution of Arctic warming to projected changes in European weather extremes and to the hazards posed to society.

UK-OSNAP: Summary What is climate? The sun's energy is constantly heating the Earth in equatorial regions, while in the Arctic and Antarctic the Earth is frozen and constantly losing heat. Ocean currents and atmospheric weather together move heat from the equator towards the poles to keep the Earth's regional temperatures in balance. So climate is simply the heat moved by ocean currents and by the weather. Earth's climate is warming: the average temperature of the Earth is rising at a rate of about 0.75 degrees Centigrade per hundred years, caused by carbon dioxide in the atmosphere trapping heat that is normally lost to space. Can we forecast how climate might change in the future? There is an old adage that rings true: "Climate is what you expect; weather is what you get". Hot weather in one summer does not tell us that climate is changing because the weather is so variable day-to-day and even year-to-year. We need to average over all the weather for a long time to decide if the climate is changing. We would like to know if the climate is changing before our descendants face the consequences, and that is where our project comes in. The ultimate ambition of climate scientists is nothing less than forecasting climate up to 10 years in advance. Is this possible? After all we know weather forecasts become somewhat unreliable after three to five days. The answer is yes because of the ocean. Slow and deep currents give the ocean a memory from years to hundreds of years, and the ocean passes this memory onto the climate. If we know the condition of the ocean now, then we have a good chance of understanding how this will affect the climate in years to come. We have set ourselves a huge task, but will be helped by colleagues in the US, Canada, Germany, Netherlands, Faroe Islands, Iceland, Denmark and Scotland. We will continuously measure the ocean circulation from Canada to Greenland to Scotland (the subpolar North Atlantic Ocean). This has never been attempted before. We have chosen the North Atlantic because the circulation here is important for the whole of Earth's climate. This is because in the high latitudes of the North Atlantic, and the Arctic Ocean that it connects to, the ocean can efficiently imprint its memory on the atmosphere by releasing the huge amounts of heat stored in it. In the UK we are on the same latitude as Canada and Siberia, and the Shetland Islands are further north than the southern tips of Greenland and Alaska, but the Atlantic Ocean circulation keeps the UK 5-10 degrees Centigrade warmer than those other countries. We can measure across an entire ocean by deploying reliable, self-recording instruments. We will use moorings (wires anchored to the seabed and supported in the water by air-filled glass spheres) to hold the instruments in the important locations. Every year from 2014 to 2018 we will use ships to recover the moorings and the data, then put the instruments back in the water. We will also use exciting new technology. Autonomous underwater Seagliders will fly from the surface to 1 km depth on year long-missions surveying the ocean, from Scotland to 2000 km westward into the Atlantic. The Seagliders transmit their data to our lab every day via satellite, and the pilot can fly the glider remotely. Also there is a global fleet of 3000 drifting floats to continuously measure the top 1 km of the ocean. Satellites provide important measurements of the ocean surface. With these new measurements, we will find how the heat carried by the ocean changes through the months and years of the project, and we will use complex computer models to help explain what we find.

Global climate change threatens our future. Urgent societal action is demanded. However, crucial uncertainties regarding the future climate still need to be addressed. Extreme climate events are wreaking enormous environmental, societal, and economic tolls and they are becoming increasingly common and intense. The huge number of uncertainties related to our future climate combine with the sensitivity of the Earth's climate system to create extremely demanding challenges. Extending our understanding for deriving effective solutions demands interdisciplinary collaboration to determine the dominant factors in climate change. Currently, there is a lack of highly qualified mathematicians with the necessary training and experience to address the diverse problems and urgent challenges posed by climate change using computational and data-driven research. Our Centre for Doctoral Training (CDT) will train new cohorts of PhD students and build a scientific community to address the grand mathematical challenges raised by the significant levels of uncertainty in our future climate. The mission of our CDT will be to prepare graduates with strong mathematics, physics and engineering backgrounds to apply their skills in mathematical modelling, scientific computing, statistics and machine learning to key climate-related problems in oceanic, atmospheric and engineering contexts. By bringing together leading experts from Imperial College London, the University of Reading and the University of Southampton along with a wide range of external partners, our CDT will be uniquely placed to equip future mathematicians with the tools required to address global climate uncertainties. Our CDT will achieve its goals by developing the mathematics and its applications that are required to understand, better predict and, ultimately, respond to impending changes in the Earth's climate and the associated risks. A particular emphasis will be the creation of a vibrant environment to integrate strong cross-disciplinary engagement and collaboration, both within and between cohorts and disciplines, in advancing the range of scientific techniques, fundamental theories, approaches and applications. This will include engaging with academics, government organisations, industry and the public. As a result, the development of outstanding skills in mathematics and science communication will be a priority. The collaborative and peer-to-peer interactions will help develop the complementary techniques and approaches that will underpin essential technical research and innovation and will be coupled with exciting opportunities to discover and advance fundamental mathematics to provide practical solutions in climate science and beyond. Our CDT will act as a seed for growing the capability and capacity to inform decisions and efforts related to climate change on a rapid timescale. The technical focus of our CDT will be enhanced by activities to appreciate the social, political and economic dimensions of societal response to climate change. Furthermore, sustained efforts to mitigate and adapt to climate change will be required during the coming decades. For this reason, along with building a professional community of graduates, the CDT will invest in imaginative outreach programmes involving school pupils and undergraduates, building on opportunities through the institutions partnering with the CDT, including the Grantham Institute for Climate Change and the Environment, the National Oceanography Centre, the National Centre for Earth Observations, the UK Meteorological Office, the European Centre for Medium-Range Weather Forecasts, and the Natural History Museum.

Changes in Ocean Heat Transport (OHT) have been associated with changes in climate over the oceans and continents. Signals such as the Atlantic Multidecadal Oscillation (an oscillation of the averaged surface temperature in the North Atlantic ocean), which drives anomalously dry/wet conditions over European, are thought to be primarily generated by basin wide fluctuations in the Atlantic Overturning Circulation and associated OHT. At the core of the link between OHT and anomalous climate conditions is a chain of events: changes in OHT result in changes in the Ocean Heat Content (OHC) over a broad range of depths, which in turn modifies the Sea Surface Temperature (SST). It is ultimately through this SST modification that the OHT changes can influence the atmospheric circulation. It has to be emphasized, however, that the OHT-OHC-SST chain is not systematic. In fact, it is likely that a large fraction of the OHT variability does only result in weak SST changes and thus little climate impact. Our current understanding of the link between OHT changes and climate variability is primarily based on statistical analyses of climate model simulations. Our proposal is that we need to understand better the mechanisms behind this link to be able to understand what the limited available observations can tell us about the ocean's impact on climate in real world, and whether or not our climate models are good approximations of the latter. Specifically, here are a few key questions that we wish to address: What makes an OHT change climatically important and potentially relevant to society? Is the OHT-OHC-SST chain properly represented in ocean and climate models? What are the implications for predictions of future climate change on the 1 to 10 year timescale of most relevance to many environmental policies of governments and businesses? To address this, we propose to explore the ocean interior dynamics that constrains the OHT-OHC-SST chain and its representation in climate prediction systems. An important innovation of the project is a methodology to evaluate the potential climate impact of OHT changes, to be used to interpret decade-long observations of the Meridional Overturning Circulation and associated OHT changes by the UK funded RAPID project and its successors. We will combine an analysis of subsurface ocean observations (Argo dataset) and ocean reanalysis products, a modeling approach with idealized models (to study physical processes) and realistic configurations (to link most readily with climate models and observations), and an evaluation of a global climate model and decadal prediction products. Besides contributing to the success of UK-funded projects (like RAPID mentioned above, but also the upcoming OSNAP), this research will also benefit the UK community in terms of evaluation and potential improvements of the UK climate models and prediction systems (UKESM1/NEMO, Met Office DePreSys).

This ambitious project will enable a step change in understanding of the sporadic but large flows of sediment, climatically-important organic carbon, and pollutants through submarine canyons, which connect continental shelves worldwide to the deep-sea. >9000 large submarine canyons occur on all the world's submerged margins, often dwarfing river systems in scale. Such canyons can transfer large quantities of natural sediments, organic carbon and nutrients that sustain important ecosystems, and are increasingly recognised as hotspots for seafloor pollution that threatens the biodiversity they host. The sediment flows that travel along canyons can be fast and dense, breaking cables that underpin global communications. It is therefore important to understand when and how such flows are triggered, the amount of material that is transported, and crucially, how these vary between types of canyon. Monitoring of turbidity currents has focused on 'land-attached' canyons fed by rivers or long-shore drift, where powerful turbidity currents have been shown to effectively transport sediment and carbon over 1000s km. Despite accounting for >70% of canyons worldwide, land-detached canyons (that lie far from shore) remain un-monitored, exposing a major gap in our understanding of global particulate transport. This bias results from a long-held view that land-detached canyons are disconnected from sediment inputs during present day sea levels. New measurements in Whittard Canyon (in the Celtic Sea, 250 km from shore) challenge this paradigm, revealing that land-detached canyons can feature turbidity currents of similar frequency and power to major land-attached canyons. These surprising new results raise the following questions, and motivate our project, which aims to determine the mechanisms and fluxes of particulate transfer via land-detached submarine canyons to the deep-sea for the first time. How can frequent turbidity currents occur if a canyon head lies far from present day sediment supplies? We will deploy an array of sensors on the continental shelf and within the Whittard Canyon head to measure the conditions before and coincident with turbidity currents, and will repeatedly map the seafloor to identify how and where sediment is transported to the canyon head. We will then make the first source to sink measurements along a land-detached canyon, and the second of any major deep-sea canyon worldwide, hence in itself this will represent a significant scientific milestone. What is the nature, concentration and burial efficiency of organic carbon or pollutants, and how does this compare to land-attached canyons? We will analyse seafloor and sediment trap samples to determine what quantities of organic carbon and pollutants are transported along the canyon, and to what extent they remain effectively locked up in the seafloor as a result of burial. Phytoplankton blooms occur at the head of Whittard Canyon during spring and summer, when turbidity currents are most frequent, providing fresh (marine) organic carbon in a similar manner to how river floods convey fresh carbon to land-attached canyons. We also observe mobile litter accumulations so will test to what extent turbidity currents transport pollutants as well as organic carbon and how its distribution relates to seafloor biodiversity hotspots. As well as posing an ecological threat, pollutants such as microplastics may effectively act as 'tracers', evidencing contemporary canyon flows. What volumes of natural and anthropogenic material are transferred via land-detached canyons? Global budgets exist for particulate transport to and across the ocean, but none include land-detached canyons. We will provide a first order calculation to assess the global significance of land-detached canyons, first assessing the contribution to deep sea transport across the Celtic Margin, and then up-scaling our results to determine what is missing from existing global budgets.