A giant dam to protect us from rising sea levels?

An "extreme" infrastructure project is needed to save cities from immersion, scientists warn. This is one possible solution.

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The floods will come, sooner or later. Sea levels are rising faster than ever before and could rise several metres over the next 80 years if greenhouse gas emissions are not reduced rapidly, according to the latest research by UN scientists. What does this mean? That we will see how the major cities of the world, including London, New York, Shanghai or Los Angeles, will end up underwater, while the world would lose 1.79 million square kilometres of land (the size of Libya in Africa).

Within Europe, the Netherlands is particularly at risk, with one third of the country already below sea level.

Possible solutions?

A Dutch scientist, Sjoerd Groeskamp, oceanographer at the Royal Netherlands Institute for of Sea Research, proposed to build two mega dams in the North Sea in an attempt to protect 25 million Europeans from this foreseeable rise in sea level. The idea is to build a giant dam 475 kilometres long between Scotland and Norway and an additional barrier approximately 160 kilometres between France and England.

"An increase of ten meters is expected for the year 2500, according to the darkest scenarios," says Groeskampy. "This dam is therefore a call to do something now about climate change".

The article, published in the American Journal of Meteorology, suggests that the cost would represent 0.1% of the annual gross national product for 20 years of all countries that would be protected by dams (it would amount to between 250 billion and 500 billion euros). According to Groeskamp, construction is "technically feasible", as the depth of the North Sea between France and England has rarely exceeded 100 metres and between Scotland and Norway the average is about 127 metres.

"We can currently build fixed platforms at depths of more than 500 meters, so such a dam seems feasible," he said. It would, however, be a construction of two dams on an unprecedented scale. The North Sea would be closed off and the Baltic Sea would lose direct access to the rest of the world’s oceans.

Consequences

The result would ultimately be the creation of a huge lake to the south and east of Britain, around western Norway, northern France, and would represent the entire coasts of Denmark, Sweden, Finland, Estonia, Latvia, Lithuania, Poland, the Netherlands and Germany. The dam would have consequences for wildlife in the North Sea, as the tide would disappear in much of the sea, carrying with it the transport of sediments and nutrients.

"The sea would eventually become a freshwater lake," Groeskamp said. "That will drastically change the ecosystem and therefore also have an impact on the fishing industry".

They cautioned, however, that the costs and consequences of doing nothing for sea-level rise would be "much higher".

Looking towards the future

The future looks frightening. If global average temperatures rise by 1.5 degrees Celsius compared to pre-industrial times, sea levels could rise to 77 centimetres by 2100, according to the Intergovernmental Panel on Climate Change (IPCC). We should not lose sight of this data, as the ceiling enshrined in the Paris Agreement is likely to be broken between 2030 and 2052 if global warming continues at its current pace, according to a 2018 IPCC report.

Reference: Sjoerd Groeskamp, Joakim Kjellsson. The Northern European Enclosure Dam for if climate change mitigation fails . American Journal of Meteorology 2020, https://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-19-0145.1 DOI 10.1175/BAMS-D-19-0145.1

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