Seasonal salinity increases on the shelf shape annual to decadal freshening in a Northeast Greenland sill fjord

As part of “Marine-Basis” program within the Greenland Ecosystem Monitoring framework 7 hydrographic transects were carried out in August between 2015 and 2021 using a SBE19+ CTD. These transects extended from the head of the fjord to the Northeast Greenland Shelf except when challenging ice conditions prevented realization of CTD casts outside Young Sound. Transects were completed within 2 days. In addition, three moorings were deployed at YS0 (20.28°W, 74.3°N), YS3.07 (20.32°W, 74.3°N), and GH5 (19.7°W, 74.17°N). YS0 and YS3.07 were inside the fjord, approximately 10 km along-fjord of the outer sill (20.22°W, 74.25°N), while GH5 was deployed on the adjacent East Greenland Shelf at ~18 km from the outer sill. Observations at YS0 covered the period between August 2016 and August 2021 while data from YS3.07 spanned between August 2017 and August 2019, and August 2020 through August 2021. Both moorings were equipped with two SBE 37SMP CTDs which measured temperature, conductivity and pressure every 10 and 20 minutes at two different depths. Instruments were serviced and redeployed each August. At YS0, the lower CTD was positioned between 62 and 68 m while the upper CTD was between 25 and 37 m. At YS3.07, CTDs were deployed at depths between 15 and 22 m and between 85 and 92 m. On the adjacent Northeast Greenland Shelf, GH5 was deployed in August 2019 and recovered in August 2021. This mooring was equipped with an SBE37SMP CTD which sampled temperature, conductivity and pressure at a nominal depth of 27-28 m. The moored CTDs had accuracies of ±0.002 °C for temperature and ± 0.0003 S m−1 for conductivity.