Historical marine datasets are available at the Carbon Portal

The OTC have submitted 941 historical marine data sets to the Carbon Portal. These datasets were taken from the data product Surface Ocean CO2 Atlas (SOCAT) version 4,  and were collected on VOS lines currently in the ICOS labelling process.

These data were collected prior to 2015 when OTC came into being and has not gone through standardised processing and quality control in accordance to the ICOS data lifecycle. They can not be considered to be official ICOS data.

The datasets can be found at the Carbon Portal data serach page (note that this search facility is under development and more features will be added). Selecting 'ICOS OTC representing SOCAT' under the 'Data submitter' filter will give you a list of links to the individual data sets.