This dataset consist of annual ocean heat measurements from climate.gov

There are three columns
year: year of observation
month: all of the months are June
heat content anomaly (10^22 Joules): ocean heat as to compared to the average between 1955 and 2006 measured in 10^22 Joules

https://www.climate.gov/news-features/understanding-climate/climate-change-ocean-heat-content