Carbon Connections: understanding the carbon interactions between adjacent marine sedimentary environments. 

<p>Annually, continental shelf sediments bury an estimated 137 Mt of organic carbon (OC) making these sedimentary systems an integral component of the global carbon (C) cycle. Within continental shelfs individual sedimentary environments can range between inshore fjord to offshore non-deltaic settings each vastly differing in their ability to trap and lock away OC. Of these different environments fjord sediments have been shown to be hotspot for the burial and storage of OC burying and estimate 18 Mt OC yr<sup>-1</sup>, which equates to ~11% of all marine C burial (Smith et al., 2015). In Scotland, the postglacial sediments of the mid-latitude fjords are estimated to store 252 ± 62 Mt OC (Smeaton et al., 2017) with a further 84,000 tonnes of OC being trapped and stored each year (Smeaton et al., 2021). It is clear that fjord sediments are an integral element of the global C cycle and could potentially be crucial long-term climate mitigation. Yet these systems do not exists in isolation and how these system interact with other marine sedimentary systems remains an open question.  </p><p>Current research is largely focused on the close interactions between fjord sediments and the terrestrial environment (Cui et al., 2016; Smeaton and Austin, 2017) but recent research in Scotland and Norway has indicated the marine environment can play as large if not greater role in the OC dynamics of fjords than terrestrial ecosystems (Faust and Knies, 2019; Smeaton et al., 2021).</p><p>Here we explore the interactions between the sediments of the Loch Linnhe fjord complex on the West coast of Scotland and the adjacent continental shelf. Using an array of geochemical techniques the source, age and depositional history of the OC held within the sediments will be investigated to understand the geochemical processes driving OC burial and storage in both the fjord and continental shelf sediments. By integrating state-of-the-art spatial analytics with the geochemical measurements we further seek to quantify how these different sedimentary settings interact and how these processes drive OC dynamics across a continental shelf.    </p><p> </p><p><strong>References </strong></p><p>Cui, X., Bianchi, T.S., Savage, C. and Smith, R.W., 2016. Organic carbon burial in fjords: Terrestrial versus marine inputs. <em>Earth and Planetary Science Letters</em>, <em>451</em>, pp.41-50.</p><p>Faust, J.C. and Knies, J., 2019. Organic matter sources in North Atlantic fjord sediments. <em>Geochemistry, Geophysics, Geosystems</em>, <em>20</em>(6), pp.2872-2885.</p><p>Smeaton, C., Austin, W.E., Davies, A.L., Baltzer, A., Howe, J.A. and Baxter, J.M., 2017. Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks. <em>Biogeosciences</em>, <em>14</em>(24), pp.5663-5674.</p><p>Smeaton, C. and Austin, W.E., 2017. Sources, sinks, and subsidies: Terrestrial carbon storage in mid‐latitude fjords. <em>Journal of Geophysical Research: Biogeosciences</em>, <em>122</em>(11), pp.2754-2768.</p><p>Smeaton, C., Yang, H. and Austin, W.E., 2021. Carbon burial in the mid-latitude fjords of Scotland. <em>Marine Geology</em>, <em>441</em>, p.106618.</p><p>Smith, R.W., Bianchi, T.S., Allison, M., Savage, C. and Galy, V., 2015. High rates of organic carbon burial in fjord sediments globally. <em>Nature Geoscience</em>, <em>8</em>(6), pp.450-453.</p>