Image: China Dialogue Ocean/zhuanlan.zhihu

China’s coastal sea levels rise accelerating

CHINA
Friday, May 05, 2023, 07:00 (GMT + 9)

The recently released China Sea Level Bulletin shows that China’s coastal sea levels in 2022 were the highest since records began in 1980.

From 1980 to 2022, sea levels rose an average of 3.5 mm per year, according to the bulletin. The rate is itself increasing, averaging 4.0 mm per year over the past 30 years – higher than the global mean for the same period. Over the past 11 years (2012–2022), China’s sea levels have consistently been the highest on record.

What will happen to China if the sea level rises by 100 meters? A rise up to 10 meters.Image:  L7 geographic/zhuanlan.zhihu

Rising sea levels – one outcome of global warming – are gradually eroding coastlines and squeezing coastal zone ecosystems. In coastal cities, they have aggravated the problems of storm surges, saltwater intrusion and even catastrophic flooding.

Data shows that a 150 mm rise in the mean global sea level, compared with 2020, would mean an increase of around 20% in the numbers of people likely to suffer a 100-year coastal flood. Over the next 30 years, China’s projected sea level rise will exceed the global average, reaching 66–165mm, the bulletin finds.

The government began national surveying work on the impact of changing coastal sea levels in 2009, and has made recommendations for addressing it.

According to observations, from 1993 to 2010, the sea level rose by an average of 3.2 millimeters per year. There are many reasons for sea level rise, one of which is the water originally stored on land entering the ocean in the form of snowfall. Photo: Manuel Bortoletti / chinadialogue Ocean

A section of the National Climate Change Adaptation Strategy 2035, released in 2022, is devoted to improving the capacity of marine and coastal ecosystems to adapt. This would be done in part by improving disaster warning and assessment systems; building disaster prevention infrastructure for coastal cities; and protecting and restoring coastal ecosystems.

The strategy also proposes adjusting design requirements for flood defences in coastal cities in accordance with rising sea levels, and strengthening coordination on adapting to the rise in the Guangdong–Hong Kong–Macau region and the Yangtze River Delta.

Global sea level rise is mainly caused by factors such as warming and expansion of sea water caused by climate warming, melting of land glaciers and polar ice caps. The communiqué pointed out that under the background of global warming, air and sea temperatures along China's coasts have increased significantly, and sea levels have accelerated.

Food Chain Collapse: A study last year showed that warming seawater has reduced the total amount of fish that can be sustainably caught by 4% since the 1930s. The worst affected areas are the Sea of ​​Japan, where warming has reduced fisheries by 35 percent, and the East China Sea by 8 percent. Photo: Manuel Bortoletti / chinadialogue Ocean

Over the past 40 years, China's coastal sea level has been rising at an accelerated rate, and its long-term cumulative effect has caused coastal ecosystem compression and tidal flat loss, affecting coastal groundwater resources, and increasing the degree of disasters caused by storm surges, coastal city floods, and salt tide intrusion. At the same time, land subsidence in coastal areas has led to a rise in relative sea level, increasing the impact of disasters.

Wang Hua said that in 2022, the high sea level along China's coast will intensify the impact of storm surges, which will have a heavy impact on the coasts of Guangdong, Zhejiang and Shandong; due to the combined effects of high sea level, astronomical tides and heavy rainfall, Zhejiang and Compound coastal floods occurred in Hainan and other coastal areas, causing large economic losses. Compared with 2021, the salt tide intrusion in the Yangtze Estuary, Qiantang River Estuary, and Pearl River Estuary has intensified overall. Coastal erosion in some monitored coastal sections of Jiangsu, Guangdong, and Hainan has intensified, and the range of seawater intrusion in some monitored areas along the coastal areas of Liaoning, Shandong, and Jiangsu has increased.

Source:  China Dialogue Ocean and China News Agency reporter Pang Wuji

[email protected]
www.seafood.media

Print