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Climate change

Where the harbours are drying out

The sea level is rising everywhere in the world, except along the coasts of Finland and Sweden. But the sea is still rising here; it's just that the land is rising faster.

von Jòn Bjarki Magnússon



 

“We should be pretty safe for now“, says Martin Vermeer, a professor of geodesy at Aalto University in Helsinki, the capital of Finland, when talking about the effects of sea level rise in his home country. While global sea level is currently rising at an average of three millimeters per year Finland´s landmass is rising three to nine millimeters per year. In Scandinavia, the so called post-glacial uplift has been ongoing for ten thousand years or since the pressure from the huge weight of the glaciers was lifted off the land at the end of last glacial period.

“Globally sea level rises by about three millimeters per year in the last decade, whereas the land uplift, the post-glacial uplift in Scandinavia for example, reaches up to nine millimeters per year, so it is about three times faster than the sea level is rising at the maximum“, says Stefan Rahmstorf, professor of Physics of the Oceans at Potsdam University and Head of Earth System Analysis at the Potsdam Institute for Climate Impact Research. „That is why many places, especially around Scandinavia, experience relative sea level drop.“

The fact that the land in Finland is rising at the same rate as the sea or even faster means that sea level is dropping everywhere along the coastline. The same goes for Finlands neighboring country, Sweden, where land is rising at similar rates. This is causing problems along the coastlines of these countries such as for the shipping industries in the area. „The conditions for sea transportation in the area is getting more tricky“, says Sven Knutsson, professor of Soil Mechanics at Luleå University of Technology.

Fennoscandian land uplift (mm/yr) relative to the centre of the Earth. Land is rising 9 mm per year where the center of the glacier was but only 1-2 mm at the old margins, for example by the west coast of Norway. (Finnish Geospatial Resarch Institute.)

The port of the town of Luleå in northern Sweden is one of the biggest in the country when it comes to shipping goods and the biggest in terms of tons passing through. An easy and open access to the Baltic Sea is fundamental for the large iron ore industry and other industries in the area. But now it is being threatened.

“The land rise itself is creating a more shallow port“, says Henrik Vuorinen, the managing director for the port of Luleå in Sweden. Vuorinen describes how the port, which was built in the mid seventies, is getting to shallow for the larger ships that are coming into the port nowadays. „During these last forty years, the land has risen by approximately half a meter due to the post-glacial rebound.“

This is why the town of Luleå is working on a project to deepen its port so that bigger ships will be able to freight goods through there. „We plan to make a rather large dredging operation to deepen the fairway into Luleå“, says Vuorinen who hopes that the new and deeper harbor will be ready by 2023. The so called Iron Port Project, which is partly financed by the European Union, will cost about 1.7 billion Swedish crowns.

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Luleå is a town in northern Sweden highly affected by the post glacial uplift that has been ongoing for last ten thousand years.

 

Drying lakes

But the shallowing sea water in the Baltic Sea is not the only thing worrying people in the area, says Sven Knutsson, professor of Soil Mechanics at Luleå University of Technology. Swedes are known for enjoying a swim in their fresh water lakes during the hot summer months but inhabitants of Luleå and surrounding areas are now worried about their lakes. As the the land rises they slowly become smaller and shallower. Knutsson describes how grass is already growing in these shallow lakes making them more dirty and less attractive than before.

“It becomes more of a muddied terrain instead of this open free space it used to be with its clear water“, Knutsson says adding that there is an ongoing discussion amongst the locals on what can be done about this. „There is a very strong debate in our city if the city should make some measures in order to keep the water surface free which is of course very expensive and they would be fighting against nature and loose anyway.“ Other things people are concerned with is the constant growth of the numerous small islands in the Baltic Sea. „Islands which were separated with water earlier are now connected“, says Knutsson.

Finland is gaining new land

Across the Baltic Sea people are facing different problems. Ostrobothnia makes up a land area in Western Finland where floods have become more common due to land rise. Martin Vermeer, a professor of geodesy at Aalto University in Helsinki, the capital of Finland, describes how land is rising faster by the coastline than further east which is causing rivers to tilt. „The big rivers flow from the east to the Gulf of Bothnia, and because of the land is rising more in the west than in the east, it is tilting“, he says adding that this can cause big river floods especially during spring time when the rivers are full of melting snow water.

Another more positive effect people in Finland are experiencing due to land rise is all the extra land that is being added to the coastline. „Finland is gaining seven hundred hectares every year due to this uplift“, says Vermeer, stressing that a very thin strip is added to the western coastline of Finland every year. „And after a generation or so it is noticeable that there is more land than on old pictures.“ Newly added land is by default owned by the state but people owning land adjoining it can claim it. This has sometimes caused a stir between neighbors claiming the same land with such issues ending up in courts.

Although the inhabitants of Finland and Sweden do not have to worry about the effects of sea level rise for now it is highly likely that will change in the near future. As the atmosphere warms the sea level will likely continue to rise at accelerating rates, says Vermeer. „As temperatures go up the sea level rise will increase further and even Finland won´t be safe after that.“

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Sea-level rising

Where the land rises faster than the sea

At first glance it's a paradox: While globally sea levels are rising, they’re sinking in Scandinavia, Greenland, Canada and Alaska. And also more recently in Iceland.

von Jòn Bjarki Magnússon

This is shown by an analysis of 365 measurement points over a period of 50 years, from 1961 to 2011. Some of the levels in the northern hemisphere are falling with astonishing speed: In certain areas of Alaska and Canada, the sea level falls by up to two centimetres per year. On the coasts of Norway, Sweden and Finland it falls by 0.7 centimetres per year. The explanation: It is not the sea level that’s falling, it is the land that’s rising. Because the glaciers are melting and the immense weight of their ice mass has disappeared. And that is why the land rises.

The phenomenon has long been known in Scandinavia. In Iceland, it’s new. In 2015, an international team of scientists published a study that showed that parts of the central highlands of Iceland rise by more than three centimetres per year. Recent measurements of the national land survey authorities show a rise by one and a half centimetres in certain coastal areas.

The reason: The glaciers that once covered approximately 11 per cent of Iceland’s land mass have shrunk dramatically in recent decades. It’s predicted that they’ll be gone completely in about 200 years time.Many countries will shrink due to climate change and the rise in sea levels. “Iceland will first grow,” says Páll Einarsson, professor at the Institute of Earth Sciences at the University of Iceland. Einarsson was one of the first who explored the phenomenon in the early 1990s. “We were stunned when we started with the measurements. Meanwhile, the land elevation is taking place at a rate much faster than we had anticipated.”

In Scandinavia, the land has been rising for a long time; it is called the “Fennoscandian land elevation”. In 1491 the residents of a settlement called Östhammar were already complaining that the coast had pulled back from the city so far that the old port had become unusable. The people at that time had no explanation for it. They suspected the sea would drain, the sea levels fall. Over the centuries, several other ports became dry, and new ones had to be built.

“During the last glacial period, one single big glacier covered what is today Scandinavia,” explains Sven Knutsson, Professor of Soil Mechanics at the Technical University of Luleå in Sweden. In its center, the glacier was about 3,000 metres thick, and its immense weight pressed the ground down. As the ice retreated about 10,000 years ago, the ground began to lift. This post-glacial uplift continues today — up to nine millimetres each year.

Professor Knutsson emphasizes how much difference this makes — especially along a coast where the water is not very deep. “This means that we are talking about a land elevation of half a metre to one metre during a person’s lifetime.”

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But there are exceptions which seem difficult to understand at first glance. Some stations on the Norwegian and Swedish coast show sea levels rising up to one millimetre per year. The explanation: These areas are the furthest away from the old Fennoscandian glacier. The land here rises only 1 to 2 millimetres per year, and sea levels rise around 3 millimetres each year globally- so the net effect is that the sea level increases slightly.

Reykjavík is another exception. Here, the sea level increased by about 2.1 millimetres per year between 1961 and 2011. The explanation: While individual parts of Iceland rise by up to three centimetres per year, the land below the capital falls due to tectonic movement. Since the launch of GPS measurements in 2007 the land around Reykjavík fell by about two millimetres per year.

Reykjavik

Reykjavik

unsplash.com / Tim Trad

If global sea levels rise by about 3 millimetres per year, and Reykjavík falls by about two millimetres per year — the sea level would actually increase by 5 millimetres per year. However, it is only 2.1 millimetres. Why?

The explanation is provided by Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research: The ice cap at the North Pole is melting due to climate change and is getting smaller. This also reduces its gravity. The water — gradually — withdraws from the North Pole, which is why countries like Greenland, Iceland, and even Scotland and Alaska, are experiencing a decline in sea levels along their coasts.

For now. In the medium term, when the global levels continue to rise, this effect will diminish — and the northern countries will experience a rise in sea levels too.