ROPEWALK (Rescuing Old data with People's Efforts: Weather and climate Archives from LogbooK records) - a digitization project for three centuries of weather observations on board of Danish ships

The project ROPEWALK, funded by the AP Møller Mærsk Fund, is a joint initiative of the Danish National Archive and the Danish Meteorological Institute over the period 2023-2026. The aim of the project is to digitize and transcribe all weather observations in ship journals and logbooks stored in the Danish National Archive.

A huge amount of data (more than 750 shelf metres) is stored in the archive, beginning as early as the 1680s. With the exception of the Napoleonic wars and the Danish state bankruptcy in 1814, the data is complete. In the archive, logbooks from Danish ships over large parts of Northern Hemisphere are found. Of particular interest are observations from two regions, the Øresund and Greenland:

In connection with the Sound duties which every ship passing the sound or belts had to pay between 1426 and 1857, weather observations were made on board of war ships placed at strategic locations near Copenhagen, Helsingør and Nyborg. These ships had to ensure that no one passed without paying the duties. Weather observations on board of these ships were tabulated starting as early as the first half of the 18th century,  and in several cases, observations were conducted every time the ship bell was struck, resulting in as many as 48 observations in the course of one day. For the oldest logbooks, which are in free text rather than in tabular form and go back to the Little Ice Age, we could locate transcriptions which are much easier to read than the original data.

The other group of logbooks which are of particular interest are from voyages to the colonies, in particular to (western) Greenland. The Greenlandic Trade Company had a monopoly for commerce with Greenland for nearly 200 years, and foreign ships would not be allowed to call a port. These "Greenland Voyages" were conducted several times per year.

In many cases, detailed sea ice observations, both from the Øresund region and the Greenland voyages, have been conducted.

The scanning of the original logbooks and journals by the National Archive in highest possible resolution is now almost complete. We have therefore initiated the transcription of the scanned documents by means of machine learning. We will present first results of this analysis.

All transcribed data will be made publicly available and can be used for future research or as input for reanalysis projects.