Oceans worldwide recorded their highest heat levels ever in 2025, absorbing an estimated 23 zettajoules of energy, according to a new international study published in Advances in Atmospheric Sciences. This represents a significant increase from 2024 and underscores a sustained warming trend in the upper 2,000 meters of the ocean. Researchers noted that while global average sea-surface temperatures were the third warmest on record, specific regions experienced record heat. This ocean warming contributes to sea-level rise and intensifies extreme weather events.