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.

The collection in the archive is remarkable for several reasons. A huge amount of data (more than 750 shelf metres) is stored, 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 particular, there were no losses during the Second World War.

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. Probably for practical reasons, weather observations were tabulated as early as the first half of the 18th century. In several cases, observations were conducted every time the ship bell was struck, resulting in 48 observations in the course of one day. The early part of the logbook collection is from the Little Ice Age, and numerous ice observations in the Danish waters have been preserved.

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 have been made.

The original logbooks are being scanned by the National Archive in highest possible resolution. The scans will then be transcribed by means of machine learning. This is possible, since the political system in Denmark was absolutistic between 1660 and 1848, and logbooks from different periods resemble each other much more than is the case for the nautical heritage in other seafaring nations. Where this is not possible, the data will be transcribed with the help of volunteers. For the oldest logbooks, which are in free text rather than in tabular form, we could locate older transcriptions which are much easier to read tahn the original data, either by machine or manually.

All transcribed data will be made publicly available. They can be used for future research or as input for reanalysis projects. We will present first results of our analysis.