Baltic Atlas of Long-Term Inventory and Climatology

The project "Baltic Atlas of Long-Term Inventory and Climatology" (BALTIC) of the Baltic Sea Research Institute Warnemünde (IOW) was first announced on the meeting of the ICES Working Group on Marine Data Management in April 2000 in Hamburg and to the ICES Baltic Committee Meeting in September 2000.

With the aim to support e.g. climate-related investigations, interdisciplinary studies, numerical modelling and regular monitoring, BALTIC is intended to provide the research community with a comprehensive "climate atlas" for the Baltic Sea, inspired by famous paradigms like the COADS (Woodruff et al. 1987) or the Levitus (1982) global oceanographic data sets, going beyond the well-known data collections of Bock (1971), Lenz (1971) or Janssen et al. (1999) in terms of a significantly more extensive observational data basis involved, but remaining pristine and unbiased by refraining from the incorporation of any numerical model data.

In the past years, a lot of historical CTD and bottle data had been reconstructed in the "Historical Data Rescue" (HDR) framework of the marine research institutes around the Baltic Sea. Starting from the data already available in the data banks of IOW, the Federal Maritime and Hydrographic Agency (BSH), and the International Council for the Exploration of the Sea (ICES), the final goal is to build a collection of virtually all accessible oceanographic observation data of the Baltic Sea. In a preceding study, it had been found that indeed much more data than presently stored in the ICES database are available to be included into this project.

In a first stage, the atlas is only based on oceanographic temperature/salinity/pressure and oxygen/hydrogen sulphide/nutrient measurements with highest possible spatial and temporal resolution. In subsequent future steps, the intended additional quantities will be those immediately derived thereof, like e.g. density, sound speed, entropy, enthalpy, pycnocline depth, or halocline depth. In further stages of development, data like density anomaly, alkalinity, biological abundances, or pollution may be added.

The first version of the BALTIC atlas covering the years 1900-2005 was finished in 2007 and is freely available for non-commercial applications from the monograph

Future extensions of it are intended to follow. To accomplish its destination as a comprehensive observational long-term data set, freely available for research and educational purposes, data from as many as possible research cruises need to be incorporated. This applies particularly to data which may have been measured in the context of specific projects or studies, safely kept in some data bank but without being looked at ever since. Hence, from its very beginning, BALTIC is a project open for support by interested cooperation partners. To overcome well-known mutual concerns in this regard, it has two data exchange policies:

A) Partners provide IOW with their original readings. IOW performs additional quality checks and processes the data into the BALTIC data base. IOW does not use these data for any other purpose, and does not pass them to third parties without permission. This costs little effort, but may cause concern about a violation of originator rights.
B) Partners perform the additional BALTIC quality checks on their own and compute for the BALTIC grid cells the statistical moments, as required for their seamless concatenation with the existing set at IOW. This method costs higher efforts, but does not interfere with the originator rights.

Up to now, the secure second policy has not been employed yet.

The 'backbone' of the BALTIC atlas is the data holding in the IOW database, collected by IOW and its precursor institutions since 1952. This basic data was extended with national (disjoint) data sets provided by partners supporting the BALTIC project, BSH (Germany), SMHI (Sweden), NERI (Denmark) and IMGW (Poland). In the following step, data from the ICES data bank were added, excluding the duplicates, i.e. all ICES data identical with the national data included already before. The data sets provided by the BED (Sweden) did not exceed the already existing ones from ICES and MIRYB (Poland). Additionally, data from EMI (Estonia) and GEOMAR (Germany) became available at a later project phase.