Land Ocean Carbon Transfer (1-year extension)

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The Land Ocean Carbon Transfer (LOCATE) programme has established genuinely new and highly effective collaborations across NOC, CEH, PML and BGS to deliver new understanding of terrigenous dissolved organic matter (tDOM) fluxes across streams, rivers, estuaries and into coastal seas and the global ocean. These fluxes collectively represent a significant and changing, yet poorly understood, component of the global C cycle. Together, we have already achieved the following, major advances: 1) the first internally consistent integration of tDOM fluxes to the tidal extent of GB rivers, demonstrating that coniferous forestry in uplands enhances this flux; 2) the largest study of tDOM transport across temperate estuarine waters, highlighting that the composition and fate of this material is strongly influenced by human activities on land; 3) the most comprehensive assessment of the distribution of tDOM throughout the North Sea, identifying that the bulk of tDOM exported from the Northwest European and Scandinavian landmasses must be buried or remineralized internally, with potential losses to the atmosphere; 4) the development of a fundamentally new model, UniDOM, that unifies concepts, state variables and parameterisations of tDOM turnover across the land-ocean aquatic continuum (LOAC). Our developments in understanding the fluxes and fate of tDOM have brought into sharp focus how little is known about greenhouse gas (GHGs; CO2, CH4, N2O) fluxes and the processes that control these in aquatic ecosystems. Our key stakeholders, including BEIS and major water companies, recognise that this lack of understanding hinders national GHG emissions reporting and the development of sustainable land- and water management policies to enable the UK government to achieve net-zero GHG emissions by 2050. Building upon our previous achievements, our proposed extension activities aim to:1) develop a GHG budget for the GB LOAC, 2) understand the biotic and abiotic processes that control these, and 3) assess the influence of human activities. We will achieve these through a series of interconnected objectives that combine desk-based syntheses and modelling activities, analysis of archived samples from our original year-long GB-scale field programme, use of our legacy focal catchments to establish a suite of baseline observations, and stakeholder engagement. We will continue to work with our diverse range of regional, national and international stakeholders to identify where and how this new understanding can achieve beneficial outcomes for policies and practices relating to C sequestration and climate regulation.