The top part of the ocean is warming up 24 per cent faster than a few decades ago. Considering that 71% of the earth’s surface is covered in saltwater, stretching down on average to 3,688 meters (12,100 ft), imagine how much hot water you’d need to make a cold bath warm again. Then think about how much heat would need to be pumped into a body of water to increase the temperature even a tiny bit.
Ninety per cent of the heat trapped by greenhouse gases goes into the oceans. The top part of the ocean is warming up 24 per cent faster than a few decades ago. And in 2019 the oceans were found to be the warmest they’d ever been since measurements began 60+ years ago .
What are the impacts?
Warming oceans kill fish and coral reefs. The stress of temperature change causes coral reefs to “bleach”, meaning they reject the symbiotic algae that live inside them, which causes them to have less energy to consume.
Healthy reefs are noisy places, imagine an underwater village full of fish singing to each other and shrimp chatting away. But bleached reefs are quiet, strange-smelling places. No one wants to stay in a ghost town, not even fish. If the reefs are bleached, this puts the fish off settling on the reef and starting their little fishy families. Without the fish there to maintain the reef by cleaning it and recycling nutrients, the reefs become quiet, lonely places. Once the coral die, it's very unlikely for the reefs to ever bounce back and this can have major issues for the whole underwater ecosystem.
Warming oceans also increase the intensity of hurricanes and coastal cyclones which can cause devastation on land. The significant rainfall during these two weather events is expected only to get worse as they become more intense. Plus, warm water takes up more room than colder water, and this is contributing to rising sea levels.