A large area of freely navigable water in which floes may be present in concentration under 1/10th; if there is no sea ice present, the area may be termed open water, even though icebergs are present.
Sea ice terminology describing a large area of freely navigable water in which ice is present, with a concentration less than 1/10. In open water no ice of land origin is present.
The interval in time from the first point atwhich an instrument or spacecraft was producing and sending data until thelast such time, ignoring possible gaps.