No abstract

Deep sea mining for poly-metallic nodules impacts the environment in many ways. A key potential hazard is the creation of a sediment plume from resuspending sediment during seabed mining. The resuspended matter disperses with currents but eventually resettles on the seabed. Resettling causes a blanketing of the seafloor environment, potentially causing harm to in-, epi- and hyperbenthic communities with possible cascading effects into food webs of deep sea habitats. Mapping the extent of such blanketing is thus an important factor in quantifying potential impacts of deep-sea mining.One technology that can assess seabed blanketing is optical imaging with cameras at square-kilometre scale. To efficiently analyse the resulting Terabytes of image data with minimized bias, automated image analysis is required. Moreover, effective quantitative monitoring of the blanketing requires ground truthing of the image data. Here, we present results from a camera-based monitoring of a deep-sea mining simulation combined with automated image analysis using the CoMoNoD method and low-cost seabed sediment traps for quantification of the blanketing thickness. We found that the impacted area was about 50 percent larger than previously determined by manual image annotation.

Across the Arctic Ocean, rapid sea ice retreat and thinning are occurring as a consequence of climate change (Stroeve & Notz, 2018). The Eurasian sector of the Arctic Ocean used to have prominent seasonal ice cover but has experienced large sea ice losses in recent years, especially during winter (Onarheim et al., 2018;Polyakov et al., 2017). The area north of Svalbard is part of the European Arctic Corridor with the greatest exchange of water in and out of the Arctic (Wassmann et al., 2010). The largest winter sea ice loss of the entire Arctic Ocean was recorded here between 1979 and 2012 (Onarheim et al., 2014), likely because of increased storm frequency and warmer temperatures of the Atlantic water (AW) advected into the area (Duarte et al., 2020;Renner et al., 2018). Unlike many regions of the Arctic Ocean that are strongly stratified, weakly stratified AW enters the area north and east of Svalbard and is exposed to direct ventilation in winter, caused by cooling and weakening of the halocline during sea-ice formation; a process called Atlantification (Polyakov et al., 2017). The shallower AW inflow

The Nansen Legacy Q3 cruise, 5-27 August 2019, initiated the seasonal investigations of the Nansen Legacy transect. The transect represent an environmental gradient going through the northern Barents Sea, and included 7 process stations (P1-P7) lasting 6-53 hrs. CTD stations were taken to increase the hydrographic resolution on the transect. The program included measurements and sampling from the atmosphere, sea ice, ocean and sea floor. Data collected ranged from physical observations, chemical, biological and geological data collection, and the aim was to link observations and measurements to improve our understanding of the systems involving both climate, human impacts and the ecosystems. Deployment of moorings and gliders extended the observational capacity in time and space, outside the cruise period.