Description: Data were collected on and off the shelf northwest of Svalbard during cruises in January, March, May, August and November 2014. The sampling depths were 1, 5, 10, 20, 30, 50, 100, 200, 500, 750, and 1000 m, as well as at the depth of the Chl a maximum. The sampling concentrated on the core of the northwards drifting warm Atlantic water, which enters the Arctic Ocean north of Svalbard either south or north of the Yermark plateau. Transects were sampled across the core of the Atlantic water inflow at 79N, and additionally at 79.4N in May and August. Heavy drift ice restricted the sampling to the shelf and shelf-break in May and August 2014. During January, March, and November, the area north of Svalbard was largely ice-free, which allowed sampling off the shelf-break into the Arctic Ocean during winter. At all stations, depth profiles of temperature, salinity and fluorescence were taken with a CTD (Seabird SBE 911 plus). Water was sampled with Niskin bottles from discrete depths for analysis of inorganic nutrients, chlorophyll a (Chl a), microbial abundance, bacterial production (BP), as well as DOM and POM. In May and August, three process stations each (in datasheet referred to as P-stations: P1, P3, P4 in May, and P5, P6, P7 in August, at these stations more time-demanding processes were investigated, such as in situ primary production and vertical export of POM. Chl a was determined by filterig 100-500mL water onto Whatmann GF/F glass fiber filters. Chl a was determined fluorometrically (10-AU, Turner Designs) from triplicates of each filter type after extraction in 5 mL methanol at room temperature in the dark for 12 h without grinding. Abundances of microorganisms: picophytoplankton, nanophytoplankton, virus, heterotrophic bacteria, and heterotrophic nanoflagellates were determined on an Attune(R) Focusing Flow Cytometer (Applied Biosystems by Life technologies) with a syringe-based fluidic system and a 20 mW 488 nm (blue) laser. Samples were fixed with glutaraldehyde (0.5% final conc.) at 4°C for minimum 2 h, shock frozen in liquid nitrogen, and stored at -80 °C until analysis. Total organic carbon (TOC) in unfiltered seawater was analyzed by high temperature combustion using a Shimadzu TOC-VCSH. All samples were acidified with HCl (to a pH of around 2) and bubbled with pure N2 gas in order to remove any inorganic carbon. Calibration was performed using deep seawater and low carbon reference waters. A blank consisting of milliQ water was analyzed every eighth sample to assess the day-to-day instrument variability. Concentration of total nitrogen (TN) was determined simultaneously by high temperature combustion using a CPH-TN nitrogen analyzer. Total organic nitrogen (TON) was calculated by subtracting the inorganic nitrogen (NOx = NO3 + NO2 + NH4+) measured from parallel nutrient samples. The instrument was calibrated using a standard series of acetoanilide and the accuracy of the instrument was evaluated using seawater reference material provided by the Hansell CRM (consensus reference material) program. For analysis of particulate organic carbon (POC) and particulate organic nitrogen (PON), triplicate subsamples (100 - 500 mL) were filtered onto precombusted Whatman GF/F glass-fibre filters (450°C for 5 h), dried at 60°C for 24 h and analyzed on-shore with a Leeman Lab CEC 440 CHN analyzer. Prior to analysis, the dried samples were fumed by concentrated HCl in 24 h before re-drying at 60°C for 24 h to remove inorganic carbon. Unfiltered seawater was filled directly from the Niskin bottles into 30 mL acid washed HDPE bottles and stored at -20°C. Nitrite and nitrate (NO-2 + NO- 3 ), phosphate (PO3- 4 ) and silicic acid (H4SiO4) were measured on a Smartchem200 (by AMS Alliance) autoanalyser following procedures as outlined in Wood et al. (1967) for NO-3 + NO-2 , Murphy and Riley (1962) for PO3-4 and Koroleff (1983) for the determination of H4SiO4. The determination of NO-3 was done by reduction to NO-2 on a built-in cadmium column, which was loaded prior to every sample run. Seven-point standard curves were made prior to every run. Two internal standards and one blank were inserted for every 8 samples and these were used to correct for any drift in the measurements. Concentration of NH+4 was determined directly in fresh samples using ortho-phthaladehyde according to Holmes et al. (1999)

Description: As marine-ice around Antarctica retracts, a vast ‘blue carbon’ sink, in the form of living biomass, is emerging. Properly protected and promoted Antarctic blue carbon will form the world’s largest natural negative feedback on climate change. However, fulfilling this promise may be challenging, given the uniqueness of the region and the legal systems that govern it. In this interdisciplinary study, we explain: the global significance of Antarctic blue carbon to international carbon mitigation efforts; the urgent need for international legal protections for areas where it is emerging; and the hurdles that need to be overcome to realize those goals. In order to progress conservation efforts past political blockages we recommend the development of an inter-instrument governance framework that quantifies the sequestration value of Antarctic blue carbon for attribution to states’ climate mitigation commitments under the 2015 Paris Agreement. Key policy insights Blue-carbon emergence around Antarctica’s coastlines will potentially store up to 160,000,000 tonnes of carbon annually. Blue-carbon will emerge in areas of rich biomass that will make it vulnerable to harvesting and other human activities; it is essential to incentivise conserving, rather than commercial exploitation of newly ice-free areas of the Southern Ocean. Antarctic blue carbon is a practical and prime candidate to build a cooperative, inter-instrument, non-market mitigation around; this should be considered at the ‘blue COP’ UN Climate change discussions in Spain. Allowing Antarctic fishing states to account for the carbon storage value of blue carbon zones through a non-market approach under the Paris Agreement could provide a vital incentive to their protection under the Antarctic Treaty System. The Scientific Committee on Antarctic Research would be the ideal body to facilitate the necessary connections between the relevant climate and Antarctic governance regimes.

Description: Carbon capture and storage by southern polar benthos is potentially the largest negative feedback on climate change. Most feedbacks on global climate change are positive; they exacerbate physical change. The few known strong negative feedbacks, those which reduce physical change, are polar, and include i) broadening existing sinks with sea-ice losses over polar continental shelves, ii) subarctic vegetation growth increases and iii) formation of new sinks where ice shelves collapse. To date, carbon sequestration gains have been recorded around the Antarctic coastal shallows where they are likely to be offset by fjordic losses associated with sedimentation, and open coast losses through increased iceberg scouring. These feedbacks are complicated by additional positive forcing associated with greater heat absorption from albedo change. In contrast there is no albedo change (negligible sea ice losses) over sub-Antarctic shelves, where rising sea temperatures are likely to increase carbon storage by animals. The continental shelves along polar continent margins and archipelagos are wide, deep and rich in life. Most species known from polar waters live on these shallower shelf regions and it has been observed that they play an increasingly important role in the carbon cycle. Carbon is transported through the system by being fixed in photosynthesis by algae, which are eaten by benthic invertebrates, and then buried when the animal dies. We aim to measure how much carbon is held per unit area of the seabed per year and how this varies in time and space. Teasing apart biological processes in these important geographic regions is vital to our understanding of global carbon capture. One of the biggest sources of error in this regard is understanding the extent to which these feedbacks are effects of climate forcing on sub-Antarctic and Arctic shelf benthos performance. This type of carbon sequestration, termed blue carbon (associated with natural processes), is likely to increase, so long as sea ice and ice shelf losses continue to be sustained. Our research project, titled Antarctic Seabed Carbon Capture Change (ASCCC) has participated in the Antarctic Circumnavigation Expedition (ACE) in 2016 and 2017 to address the question ‘How will regional warming influence how much carbon is captured and stored by life on the seabed around Antarctica and the sub-Antarctic?’, from which we plan to estimate increased benthic carbon stored across the southern polar region due to recent ice shelf losses, sea ice losses and temperature increases.

Description: Continental shelves around Antarctica are a globally important carbon sink, due to both oceanographic CO2 absorption and biological fixation and trophic cascading. Most carbon passing through the foodweb is pelagic and is recycled through microbial loops. However significant masses are accumulated and immobilized (within calcareous skeletons of benthos), accounting for sequestration potential of 106 tonnes per year. Burial potential is enhanced by being largely untrawled by human harvesting and too deep for iceberg scouring. Yet these are also true for subAntarctic island shelves where there are considerable phytoplankton blooms, little or no sea ice and warmer sea temperatures (enabling faster meal processing time by benthos) – yet their potential as a carbon sink has been largely ignored. We report on the Antarctic Seabed Carbon Capture Change (ASCCC) project which sampled most of the high southern latitude continental shelves during the 2016/17 Antarctic Circumnavigation Expedition (ACE). Video and photo- equipped trawls collected imagery and benthos samples allowing us to estimate changes in intra and inter-shelf variability in benthos density and biomass. Growth models constructed from age structure of sampled species with growth check lines (e.g. bryozoans, bivalves, brachiopods etc) enable annual carbon accumulation to be estimated. Preliminary data and analyses suggest that continental shelves of 40-55°S may be globally significant, both in terms of absolute carbon storage but also in trying to reduce error in climate models. See www.asccc.co.uk