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Over a 6 million square km region of the central Pacific ocean, at abyssal depths of almost five thousand metres, lies a vast mineral resource in the form of small potato-sized deposits called polymetallic nodules. They are highly-enriched in metals of importance for industry, including the development of new sustainable technologies. Although the region lies in international waters, countries have now signed 16 exploration contracts with a UN-organised international regulator and the United Kingdom is sponsor to two of these, covering an area more than the size of England. It is a requirement of both the regulator and the sponsoring state to ensure that serious harm is avoided to the marine ecosystem in this region - a hitherto untouched deep-sea wilderness. Developing a sustainable approach to polymetallic nodule mining is a challenge as the nature and importance of the Pacific abyssal ecosystem is largely unknown, as are the capacity of the ecosystem to cope with and recover from mining impacts. Our project aims to provide the critical scientific understanding and evidence-base to reduce the risks of this industrial development, taking advantage of two new and unique opportunities to solve these problems in a single programme. Firstly, the UK contractor that holds the UK-sponsored exploration contract (UK Seabed Resources) is planning a mining test in 2023, which will allow us to test the immediate impacts of a seabed mining vehicle for the first time. Secondly, as a partner in the first full-scale mining test done in 1979, they have been able to release new data on the location and results of a 40-year old large-scale mining operation. Our project team have secured access to data and test plans, to allow detailed experimental evaluation of impact and recovery from realistic mining disturbance on a decadal scale of vital relevance to understanding the long-term sustainability of deep-sea mining. The project aims to better understand the ecosystem in the Pacific abyss and how the different components interact and interconnect. We will start by assessing the water and its dynamic flows over time and space. This complex physical environment will be monitored for a year to capture its variabilities, particularly "storm events" near the seabed. We will use this to make predictions about where the sediment plume generated by mining will be transported and settle back to the seafloor. We then assess the linkages between the water, sediment surface and sub sediments, evaluating the natural cycling of nutrients and metals that is important to maintain ecosystem health. The impacts of mining and recovery of these processes will be assessed. Mining will lead to changes in the structure of the seabed, its shape and the physical nature of the sediments, which will be mapped and linked to biological patterns. The biological processes that lead to these patterns will be assessed by detailing the life histories and reproduction of the organisms present and their connectivity between areas near and far, and then determining their role in maintaining structured communities of life, a high biodiversity and a functioning food web. We will then evaluate the functions in the ecosystem that these organisms provide, which help maintain a healthy ecosystem. The impact of mining and recovery of all these patterns and processes will be determined using our experimental areas to assess the biological and functional consequences of disturbance in the deep sea. These changes are likely complex, so a range of mathematical models will be used to better understand and predict the consequences of mining activities at larger time and space scales. Such predictive power, along with the evidence from the scientific assessment, will provide information that is critical for understanding and reducing the environmental risk of future mining activities.

Ocean noise levels have increased substantially over the past 50 years. Shipping, resource exploitation and offshore construction increasingly dominate ocean soundscapes. At the same time, sounds of biological origin are reducing due to overfishing and habitat degradation. Climate change is affecting natural sounds, for example due to changing ice conditions in polar regions. Existing evidence shows that noise affects marine animal behaviour, physiology and can have direct impacts on their survival. Ocean sound thus plays a central role in the health of ocean ecosystems, and it is important for offshore industries and regulators to know whether and where it is increasing or decreasing. Finally, ocean sound measurements can also be used for quantification of wind speed, the observation of air-sea interactions and to study extreme weather events. Passive acoustic monitoring (PAM) is a transdisciplinary approach to monitoring ocean sound, including anthropogenic activities, biological sounds, and physical processes. However, long-term observations of ocean soundscapes are hampered by the high costs of ship-based instrument deployments in remote marine regions. Autonomous ocean gliders provide a solution to this problem, as they can cover large spatial scales and depth ranges at reduced economic and environmental costs. Ocean gliders are ideal for PAM applications. They glide quietly without propulsion noise, and they can carry one or several hydrophones, offering multiple acoustic monitoring possibilities, including near real-time detection and localisation of protected species. Further, gliders collect environmental data, such as temperature and salinity, which allow estimates of the sound speed profile, important for sound propagation modelling. These variables also provide context for species distribution and habitat models. The 10 standalone acoustic recording units which will be integrated in the UK ocean glider fleet will provide a step-change in the UK's national capability in ocean monitoring. This new capability will build capacity within the wider UK research community to enable dedicated or opportunistic PAM observations within ongoing glider-based ocean observation programmes, such as CLASS and AtlantiS, and facilitate new ocean sound focussed research in UK waters and global oceans. Cross-institute access to PAM equipment integrated in the UK glider fleet presents an overdue, next step towards building a more comprehensive approach to global ocean observations. Obtaining this national capability is particularly timely, as ocean sound has recently been recognised as an Essential Ocean Variable (EOV) by the Global Ocean Observing System (GOOS). Studying this EOV will advance our understanding of physical ocean processes, how different anthropogenic sources affect ocean ambient sound, the effects sound has on marine life, and how acoustics can be used to assess biodiversity and ecosystem health. Such knowledge is essential for mitigating human impacts and protecting ocean environments and associated ecosystems. The required infrastructure and logistics to undertake glider-based PAM are already in place at the Marine Autonomous and Robotics Systems (MARS) facility at the National Oceanography Centre (NOC) and the Scottish Association for Marine Science (SAMS), where the equipment will be based. The acquisition of integrated acoustic equipment for ocean gliders will establish new and strengthen existing science collaborations and provide a long-term data resource for scientists, policymakers, offshore industries, and their regulators.

Human activities have caused atmospheric CO2 levels to increase dramatically, but their growth has been slowed by the oceans absorbing approximately one quarter of this anthropogenic carbon (Canth). Globally, the North Atlantic Ocean stores the highest quantities of Canth, due to local CO2 uptake from the atmosphere, and large-scale ocean currents, particularly the Atlantic Meridional Overturning Circulation (AMOC) delivering waters high in Canth to northern locations where they cool, get denser and sink to great depths away from contact with the atmosphere. Models project that the size of this carbon sink will reduce in the coming decades despite continued atmospheric CO2 increases, as surface warming increases stratification, decreases CO2 solubility, and AMOC weakening slows the transport of dense waters to depth. However there is substantial model spread regarding flux peak, and decline timing. The same models show a large range in ocean carbon transports, often related to AMOC representation. The balance between air-sea fluxes and ocean transports to North Atlantic Canth accumulation is thus not well constrained both now and into the future, and subject to large uncertainties. Previous observational studies have attempted to quantify the contributions of these processes to Canth accumulation in order to assist with model verification and validation. However, it is not currently possible to directly measure anthropogenic air-sea CO2 fluxes - they are chemically identical to those with 'normal', non-human-derived CO2. And while they can be calculated indirectly from trans-ocean basin decadal repeat cruises, this approach is subject to large uncertainties. It is thus impossible to constrain why fluxes (or carbon transports) vary on shorter timescales, or how they interact with the AMOC. For this we require frequent estimates of ocean transports combined with frequent estimates of how quickly carbon concentrations are increasing in the ocean. This project will look to do precisely that. Firstly, we will generate new high-resolution estimates of Canth transports across the subtropical and subpolar boundaries of the North Atlantic, relying on the outputs from the RAPID (10day) and OSNAP (monthly) mooring arrays. At RAPID, we will extend to 2024 the 2004-2013 time-series we published in 2021 and that identified a stable, northward Canth transport that was highly variable over all time scales (weekly, monthly, seasonally, annually, interannually), and highly correlated to the AMOC. We will collect new sub-seasonal water samples in Florida Straits, at the western boundary. The waters that flow through the Straits represent the vast majority of the upper, northward-flowing part of the overturning circulation but we don't currently account for any variability in water mass characteristics (chemical or otherwise) in the transport calculation there, so are not fully characterising the AMOC:carbon coupling. We'll generate a novel Canth transports time-series for 2014-2022 at the OSNAP, identifying how it co-varies with AMOC, and RAPID carbon transports. We'll track the changing interior (anthropogenic) carbon signal using novel, publicly-available datasets based on ship and autonomous platform data. Combined, we'll form a North Atlantic budget with transports at the southern and northern boundaries, and evolving concentrations in the interior. The residual will represent Canth entering (or leaving) through the surface - the air-sea flux. The contributions of air-sea fluxes and ocean circulation to regional carbon accumulation will be determined, better understanding how, with AMOC, they work together to store carbon. The calculation scheme, its components and transport/air-sea flux/AMOC relationships will be tested in earth system models, before observations are compared to simulation outputs. Our findings will help improve the accuracy of climate models, which is crucial for predicting the effects of climate change.

The receding Greenland Ice Sheet (GrIS) is now the largest contributor to global sea-level rise. A major driving force behind this recession is the encroachment of warm ocean water through fjords to the faces of marine-terminating outlet glaciers (MTOGs) that drain the ice sheet. Satellite data confirm that these glaciers have thinned, accelerated and retreated over the past few decades, but with significant temporal and spatial variability. Despite this information, our ability to predict how, and at what rate, the ice sheet will respond to future warming is made difficult by a lack of direct observations from these remote and often ice-infested areas and by the limited time-series of existing datasets. Constraining Greenland's likely decay trajectory is necessary to evaluate policy options with regard to its contribution to sea level rise. However, the wider effects of this decay also encompass the marine environments bordering the landmass. Increasing the supply of freshwater to these areas (as meltwater and icebergs) alters circulation patterns and impacts North Atlantic weather systems, including those affecting the UK. It also brings nutrients to offshore areas that promote marine productivity, which in turn has the potential to draw down more atmospheric CO2 and bury organic carbon in fjord and shelf sediments. To date, these processes have not been quantified and we need to improve our understanding of this negative feedback to climate change before it can be incorporated into predictive models. One way to determine which ice-ocean-marine ecosystem scenarios are analogues for future warming scenarios is to extend the record of modern observations back over the last 11,700 years of the Holocene using proxies from marine sediment cores. A few records of 20th Century iceberg calving and warm water encroachment exist around Greenland but there are no comprehensive, coupled records of past glacier change, ocean warming and marine productivity for earlier periods. Here, we propose to generate these long-term records for the Holocene era for a key location in SE Greenland (Kangerlussuaq Fjord) calibrated by observations of the present-day system over three annual cycles. We will then use numerical modelling constrained by our new data to test how the Greenland Ice Sheet responded to climatic warming during the Holocene, particularly during the Holocene Thermal Maximum when summer temperatures were analogous to those predicted for 2100. We will acquire a full suite of oceanographic, biological and geological observations during a 6-week multidisciplinary cruise to SE Greenland on the UK's new polar research vessel, the RRS Sir David Attenborough, making full use of its state-of-the-art capabilities as a logistical platform. We will use cruise datasets to determine modern interactions between warm water inflows and glacial meltwater outflows, and to quantify marine productivity, sedimentation and nutrient cycling. At the same time, we will collect long and short marine-sediment cores and terrestrial rock samples to constrain past changes in glacier dynamics and derive coupled proxy records of ocean temperatures and carbon burial/storage. To do this, we will calibrate the sediment-core signals with our modern observations using an anchored mooring and repeat observations.