Comparison of in-situ measurements from the Norströmsgrund lighthouse to Copernicus reanalysis products

Abstract

Here, we aim to extend the full-scale data measurements of ice conditions and the resulting structure behaviour at the Norströmsgrund lighthouse to other locations in the Baltic Sea via comparison to the met-ocean conditions from Copernicus reanalysis products. The sea ice velocity produced by the global reanalysis product of the Copernicus Marine Environment Monitoring Service compares favourably to the measurements taken at Norströmsgrund, producing a skewed lognormal similar to the distribution observed during the measurement campaigns. The sea ice thickness from the reanalysis is less applicable; the inspected model produces estimates of level ice thickness near Norströmsgrund over an area of approximately 9.3 km x 3.9 km, averaging out the effect of ridges and leads. A transformation from level ice statistics to first year ice statistics is thus required for application to other locations in the Baltic Sea. Atmospheric reanalysis of air temperature, barometric pressure, wind speed, and wind direction match perfectly over a much larger area (approximately 83 km x 35 km near the Norströmsgrund lighthouse). Comparison to met-ocean conditions both on-site and via Copernicus reanalysis products show some evidence that frequency lock-in events are connected to changes in local conditions; further analysis is required for confirmation.