The data sets referred to on this web page are collections [see data sources Northern Hemisphere and data sources Southern Hemisphere] of visual ship-based sea-ice observations carried out from the ship's bridge while the ship cruises through the sea ice. These observations have been standardized according to the ASPeCt protocol and for the Arctic additionally according to the ASSIST/IceWatch protocol. These observations contain the ship's position, the day and time of the observation (hourly, with an observation radius around the ship of about 1 km), the total sea ice concentration, the partial concentrations of the three thickest sea ice types, and for these, respectively, thickness, type, fraction and height of deformation sea ice, floe size, snow properties and depth, and for the Arctic also melt-pond fraction.
For more information see, e.g.: https://icewatch.met.no/ and https://data.aad.gov.au/aspect/ . A tutorial allows to learn how sea-ice observations are carried out according to the ASPeCt protocol.
The two pictures at the top illustrate how the sea ice thickness is estimated by looking at the tilted ice floe and a scale attached to the ship's hull (in this case the research icebreaker Polarstern).
There are two kinds of this data offered here. The first kind is the original ASPeCt observations data file covering expeditions into the Antarctic of years 1980 through 2005 (see Worby et al., 2008).
The second kind are data files with a collection of the more recent observations, hence extending the original ASPeCt observation data set through 2015, and adding observations collected in the Arctic (Data of years 2006 through 2015 for the Arctic are part of the data set of Hutchings, 2018, see references). Cruises considered in the current release at ICDC are from May 2002 through December 2015.
This data collection has been updated at ICDC on April 12, 2019.