BEIJING, Jan. 18 (Xinhua) -- The temperature of oceans in 2017 reached a record high, the Chinese Academy of Sciences (CAS) said Thursday.

According to the CAS Institute of Atmospheric Physics, compared to 2015, the year with the second warmest ocean on record, the extra heat in the upper two kilometers of sea water across the globe in 2017 represented 700 times as much as energy as China's electricity use in 2016.

The Atlantic and Antarctic oceans warmed up the fastest, as warming has already taken place in most of the other seas.

The marine ecosystems remains in jeopardy as a result, with coral reefs and the creatures that live on them threatened, researchers at the institute said.

The expansion caused by warming contributes to rising of sea levels, while more sea ice and ice shelves will melt and ocean currents will be affected.

The heat content of the ocean is a key indicator of climate change. Due to its high specific heat capacity, sea water contains the main signals, as it stores 90 percent of the energy for global warming.