- Our oceans are much warmer than we previously thought, according to a new study. They are also heating up faster than was believed, driven by climate change caused by humans.
- The study, published this week in the journal Science, showed that the world’s oceans have got much warmer since the 1960s. Its authors said 2018 would be the warmest year on record for oceans.
But what happens when the oceans get warmer, and what does it mean for us?
- When water heats up, it takes up more space. That means as oceans warm, sea levels rise. The study says this effect alone could make sea levels rise 30cm (12 inches) by the end of the century. “That doesn’t sound like much, but there are many large cities around the world, much built on reclaimed land, that are not more than 30cm above sea level.
- But on top of that, warming oceans are causing polar ice sheets to melt faster, which will make sea levels rise even more. The combination of melting ice and expanding water could cause sea levels to rise by up to a meter by 2100. Hundreds of millions of people could be forced to leave their homes.
- Warmer oceans make tropical storms more intense and longer lasting.
- Warming temperatures also mean changing rainfall patterns.
- Coral reefs are especially sensitive to warmer seas. Between 2016 and 2017, half the corals at the Great Barrier Reef were killed by two ocean heat waves. Almost three-quarters of the world’s coral reefs were affected by those heat waves and experts say warmer oceans mean these sorts of die-offs will become much more common.
- Another problem for sea life is that increased flooding causes more nutrients to be washed into the sea. This leads to plankton blooms and ultimately causes some parts of the sea to be starved of oxygen, making it hard for fish to live there.
- Warm oceans hold less oxygen, which makes the problem worse.
- Fish species respond to warmer oceans by migrating to cooler areas.
- There is a severe food security risk in the tropics.
- Warmer seas are causing sea ice to melt. Sea ice floats on the ocean surface, so when it melts it doesn’t affect sea levels. It’s bad news for animals that depend on sea ice to survive — including polar bears. But it’s also a problem for some Arctic communities.
- The only positive is we now have a better understanding of the relationship between human emissions and ocean warming. “That gives stronger evidence as to why controlling emissions is so important for our generation — and the next.”