NOAA@NSIDC is pleased to announce that the Arctic Sea Ice Concentration and Extent from Danish Meteorological Institute Sea Ice Charts, 1901-1956, Version 1 data set has been updated to Version 1.1. Version 1.1 adds quarter-degree gridded fields of sea ice concentration in NetCDF format to the existing shapefile and image representations of ice concentration from the Danish chart series.
The data set is derived from Arctic Sea Ice Charts from Danish Meteorological Institute, 1893 - 1956, Version 1. These charts show observed and inferred sea ice extent for summer months based on compiled observations reported by a network of national organizations, shore-based observers, scientific expeditions, and ships. Symbols drawn on the charts give an indication of ice conditions in regions, usually near the ice edge, where ice was observed. We used these to estimate ice concentrations in these regions. The Danish mapmakers inferred a circum-Arctic ice edge where ice was not observed. In our derived product, ice within this edge is flagged as present and is not given a concentration.
The Danish charts have been used for research since the earliest attempts to understand the role of sea ice in the global heat budget. Providing the chart information in NetCDF format builds on a legacy that includes work to digitized the charts that was done in the 1970s by P. M. Kelly, J. Walsh, and others. Much of this work is described in the NSIDC Glaciological Data series. See the User Guides for Arctic Sea Ice Charts from Danish Meteorological Institute, 1893 - 1956 and Arctic Sea Ice Concentration and Extent from Danish Meteorological Institute Sea Ice Charts, 1901-1956 for links to these in the References.
To access these data and view the documentation, visit the data set landing page.
Data Set DOI: https://doi.org/10.7265/N5MP517M