Cruise report Atlantic-Arctic Ocean Change (AOC2025)

The cruise was to the southern Greenland Sea, in particular waters west and northwest of Jan Mayen. The focus was on: i) tracing the path of freshwater from sea ice melt and the east Greenland current into the Greenland Sea, ii) studying the optical properties and characteristics of the spring phytoplankton bloom, iii) quantifying the impact of associated zooplankton grazing and vertical fluxes of carbon, iv) investigating the production and character of volatile organic carbon released by the bloom, and v) mapping the seafloor and collecting sediment cores to derive reconstructions of conditions during the Holocene. Ice conditions limited the western extent of operations so that all stations were in the Greenland Sea and along the ridge extending between Greenland and Jan Mayen. Underway from Tromsø the newly installed multi-beam was tested and prepared, and the underway thermosalinograph started. Water column and seafloor sampling started at ~5W, 73N on the 19th of May, with a transect along 73N. By ~7W the transect was ceased due to difficult ice conditions and a new transect further south was initiated at ~6W, 72.5 N and continued westward to ~11.5W where we reached the ice edge and which we then followed SW to make a new transect sailing east along 72N from ~12W to 7W. The next transect started at ~8W, just North of Jan Mayen, and progressed westwards along 71.5 N to 16 W. We then proceeded to stations and seafloor mapping of a seamount within a triangle near the ice edge (13.5W/71.5N, 14.5W/72, 16W, 71.5N). The final transect extended westwards along 71N, between ~16W and 10.5W. At approximately midday on the 31st of May sampling activities ceased and the ship commenced its return to Hirtshals. Sampling activities in the study region included, vertical profiles of water column properties, water column samples, vertical plankton net hauls, sediment coring and sea floor mapping with a multibeam and sub-bottom profiler. Two ARGO float deployments were planned but only one was completed as the second float was found to have a fault.