This dataset contains gridded Sea Level Anomalies (SLA) for the North Sea, computed from multi-mission satellite altimetry at DGFI-TUM. SLA are provided in monthly temporal resolution between May-1995 and May-2019. The high-frequency cross-calibrated SLA observations are gridded by a least-squares approach on an unstructured triangular mesh with a spatial resolution of 6 – 8 km. The grid nodes cover the investigation area from 4°W to 12.2°E and from 50°N to 61°N. The data is provided as Format 4 Classic NetCDF files and contains beside the SLA values, uncertainty and auxiliary information per grid node. Moreover, a Mean Sea Surface (namely the DTU15MSS (Andersen et. al, 2016)) is included and enables a transformation from SLA to Sea Surface Heights (SSH).
The SLA estimates are corrected using latest atmospheric and geophysical corrections and by the application of the ALES retracker (Passaro et al., 2014) in the case of conventional altimetry missions and by ALES+SAR (Passaro et al., 2020) in the case of Delay-Doppler altimeter observations. More information regarding the corrections and pre-processing of the along-track SLA measurements are provided in NorthSEAL: A new Dataset of Sea Level Changes in the North Sea from Satellite Altimetry
In addition to SLA, information concerning sea level (SL) trends and the annual cycle are provided for each grid node. For the investigation period, absolute SL trends range in the order of 1.5 to 3.5 mm/year, with a basin average trend of 2.61 +- 0.95 mm/year. The mean value of the correlations of the data with tide gauge (TG) observations is 0.85, which exceeds correlations based on currently available global gridded SL dataset. The accuracy of the linear trends - assessed by a comparison with Vertical Land Motion (VLM) corrected TG observations - is in the same order of magnitude as similar products: RMSE of 1.4 mm/year when correcting with GPS VLM estimates; RMSE of 1.15 mm/year when correcting with GIA VLM. More information regarding uncertainty information can be found in the related publication.
