While NASA does perform some remote sensing for ocean research, the main federal agency in charge of ocean research is the National Oceanic and Atmospheric Administration (NOAA).
This is their research website: https://research.noaa.gov/Labs-Programs/oar-programs. It has a link to their NOAA Office of Ocean Exploration and Research.
Examples of NASA activities and missions supporting ocean monitoring and research are:
- Oceanography - NASA Science Mission Directorate
- Grace Mission and GRACE-Follow-On
- Aquarius
- SWOT
- SeaSat, Topex/Poseidon, Jason…
