China’s coasts feel the heat of rising sea levels
- The country needs to protect its coastline and make sure it can adapt to cope with storm surges, erosion and salt tides, report says
- Increase in global temperatures is causing ocean water to expand and land ice to melt, expert says
Sea levels along China’s densely populated coastal provinces are rising faster than ever, sending the water line up to 42 metres inland in some places, according to the Ministry of Natural Resources.
In an annual report released on late last month, the ministry said sea levels around the country rose an average of 3.4mm (0.13 inches) a year from 1980 to 2020, up from the 2.6mm 30-year average in 2010.
In the next 30 years, China’s coastal sea levels were expected to rise by 55-170mm, the report said, urging preventive action.
“China should protect its coasts ... and improve the country’s ability to adapt to rising sea levels,” it said.
The reported increases are on a par with figures worldwide, with the best estimates putting the global average rise in the past decade at 3.6mm per year, according to Benjamin Horton, director of the Earth Observatory of Singapore at Nanyang Technological University.
“About a third of its current rise comes from thermal expansion – water grows in volume as it warms. The rest comes from the melting of ice on land.”
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The ministry said that in 2020, the average temperatures around the world were 1.2 degrees Celsius higher than pre-industrial levels and among the warmest on record.
The report said sea level rises intensified storm surges, erosion and salt tides, with provinces such as Zhejiang and Guangdong provinces hit particularly hard. In Zhejiang alone, Typhoon Hagupit inflicted more than 73 billion yuan (US$11.3 billion) in agriculture and infrastructure losses when it hit in August.
The report said that while there had been improvements overall in coastal erosion since 2019, conditions had deteriorated in Liaoning, Jiangsu, Fujian and Guangxi. In Yancheng, Jiangsu province, the water line moved as much as 42 metres (138 feet) further inland last year, the report said.
Concerns of saltwater contaminating freshwater supplies had grown in the past year for Liaoning, Hebei and Jiangsu provinces.
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Compounding the problem is China’s practice of groundwater extraction that causes land subsidence. “People are pumping out the water from rocks below cities and towns. That lowers the land surface at the same time that the sea levels are rising. So more of the housing, factories and power stations are becoming more vulnerable,” said John Moore, chief scientist at the College of Global Change and Earth System Science at Beijing Normal University.
Moore said another cause of concern was the increasing frequency of floods as sea levels rose.
“The mean sea level has a dramatic impact on the return frequency of large floods. If you have an event that is expected once every 100 years, a rise in sea level by 30cm – which is less than what we expect to happen this century – that ‘100-year flood’ becomes something you expect almost every year,” he said.
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Moore said that by 2100, the world’s oceans could rise by a metre. In the worst-case scenario where Antarctic ice loss was left untackled, sea levels could rise by 2 metres.
“We are pretty much stuck with at least 30cm of sea level rise this century, simply because of the heat that the ocean has absorbed over the last few centuries,” Moore said.
The big question is the melting of giant ice sheets in Greenland and Antarctica.
“If all the ice in Greenland melted, it would raise global sea levels by seven metres,” Horton said.
“Antarctica is a giant, twice the size of Australia, two to three kilometres thick. It has enough water to raise sea levels by 65 metres. If a few per cent of the Antarctic ice sheet were to melt, it would cause devastating impacts.”
