The NOAA National Centers for Environmental Information (NCEI) manages the world's largest collection of freely available oceanographic data. The oceanographic archive includes data dating back to the 1700s from every imaginable platform and from every corner of the world ocean. NCEI is the merger of NOAA's three former National Data Centers: The National Oceanographic Data Center (NODC), the National Climatic Data Center (NCDC), and the National Geophysical Data Center (NGDC). Currently, the holdings of the former NODC are available through DataONE though NCEI is investigating the possibility of including more of its environmental data holdings from the atmospheric, climatic, and geophysical domains.
NOAA NCEI Oceanographic Data Archive