Last year was the hottest year on record for Earth’s oceans, according to two scientists at the Institute of Atmospheric Physics at the Chinese Academy of Sciences (IAP/CAS). The increase in ocean heat led to a 1.7-millimeter global sea level rise – and other consequences like “declining ocean oxygen, bleaching of coral reefs, and melting sea ice and ice shelves.”

Ocean, wave, waves, beach, sand, water, Russia

The ocean absorbs over 90 percent of the planet’s “residual heat related to global warming,” according to the researchers, Lijing Cheng and Jiang Zhu, whose work recently came out as an early online release in the journal Advances in Atmospheric Sciences. While they said the increase in ocean heat content for last year happened in most of the world’s regions, the Atlantic and Southern Oceans displayed more warming than the Indian and Pacific Oceans.

Related: Rising ocean temperatures are cooking the Great Barrier Reef to death

According to National Geographic, the two scrutinized ocean temperature data from multiple institutions, including the United States’ National Oceanic and Atmospheric Administration. Scientists started gathering the data during the 1950’s – and in the late 1990’s, ocean temperatures started to take off, per the publication. The IAP ocean analysis reveals “the last five years have been the five warmest years in the ocean.”

Ocean, wave, waves, beach, sand, water, Russia

National Geographic pointed out people visiting the beach probably wouldn’t notice the temperature rise, but a warming ocean could still have damaging impacts. Sea ice coverage and thickness have both taken a hit. And the window to save Earth’s coral reefs is closing quickly.

The researchers said in their paper, “The global ocean heat content record robustly represents the signature of global warming…The human greenhouse gas footprint continues to impact the Earth system.”

+ Advances in Atmospheric Sciences

Via Institute of Atmospheric Physics, Chinese Academy of Sciences, The Guardian and National Geographic

Images via Deposit PhotosAnt Rozetzky on Unsplash and Tim Lautensack on Unsplash