Scotland’s Pockmarks: understanding the link between gas-escape features and buried carbon in fjordic systems

Scotland’s fjords and firths are important stores of organic and inorganic carbon – often referred to as ‘blue carbon’. Despite being recognised three decades ago as major carbon stores and globally important sequestration sites, quantifying the blue carbon in fjordic sedimentary systems has remained a largely neglected topic. Recent ground-breaking work has provided the first estimates of total carbon storage within marine sediments around Scotland (Burrows et al., 2014; Smeaton et al., 2016). The more recent of these studies shows that the original estimates of organic carbon within Scotland’s fjords significantly underestimates the actual total, probably by around two orders of magnitude.
Pockmarks – roughly circular, crater-like, depressions in the sea bed – are currently known to occur preferentially within Scotland’s fjords and coastal waters. Initial research has shown that the highest abundance of pockmarks around western Scotland are found in sediments within several recently designated Marine Protected Areas (MPA) and/or Special Areas of Conservation (SAC). These pockmarks typically occur within fine-grained glacial or postglacial fjordic sediments known to be important repositories of blue carbon. High productivity biomass and burrowed mud habitats are also well represented within these MPAs/SACs.
This project will aim to formalise and understand the relationship between organic-rich sediments, gas-escape features (pockmarks) and blue carbon stocks in Scotland’s fjords, specifically within MPA designations.
This project has three primary aims:
• to map and quantify the distribution and morphological variation of sea-bed pockmarks in waters around western Scotland (focusing on MPAs / SACs);
• to quantify the degree of bathymetric and geological control on pockmark morphology and formation;
• to assess the relationship between pockmark distribution, shallow sub-sea-bed gas storage, and potential sedimentary carbon stocks in fjordic sediments.