Nov 28 2012 , Sweden
Nations rise from sea
In contrast to worries from the Maldives to Manhattan of storm surges and higher ocean levels caused by climate change, the entire northern part of the Nordic region is rising and, as a result, the Baltic Sea is receding. “In a way we’re lucky,” said Lena Bengten, environmental strategist at the Lulea Municipality in Sweden, pointing to damage from Superstorm Sandy that killed more than 200 people from Haiti to the US.
The uplift of almost a centimetre (0.4 inch) a year, one of the highest rates in the world, is part of a continuing geological rebound since the end of the Ice Age removed a vast ice sheet from regions around the Arctic Circle. “It’s a bit like a foam rubber mattress. It takes a while to return to normal after you get up,” said Martin Vermeer, a professor of geodesy at Aalto University in Finland. Finland gains 7 sq km (2.7 sq miles) a year as the land rises. In the Lulea region just south of the Arctic Circle, mostly flat with pine forests and where the sea freezes in winter, tracts of land have emerged, leaving some Stone Age, Viking and Medieval sites inland.
That puts human settlements gradually out of harm’s way from sea flooding, unlike low-lying islands from Tuvalu to Kiribati or cities from New York to Shanghai. Facebook is investing in a new data centre in Lulea on land that was once on the seabed.
But rising land also means costs. Lulea is planning to deepen its port by 2020 to let in bigger ships and offset land rise at a cost of 1.6 billion Swedish crowns ($237.86 million). “Even if we didn’t have the ambition to have larger ships we would still have to do it on a smaller scale just to compensate for the land rise,” said Roger Danell, head of the port.
Dredging just for existing ships would cost 400 million crowns as the water gets shallower at the port that was last deepened in the 1970s, construction manager Jeanette Lestander said. Main exports are iron ore and the main import is coal.
But a projected rise in sea levels due to global warming means dredging to offset land rise for the next 40 years will be slightly less than in the 1970s.
“The rate of sea level fall will be slowing,” Lestander said during a visit to the port. The future sea fall is estimated at 0.7 cm a year from 0.9 cm. In the north of Sweden, 200 km inland and 170 metres above current sea level, archaeologists recently found a 10,700 year-old Stone Age hunters’ camp near Pajala that was originally by the Ancylus Lake, the forerunner of the Baltic Sea.
“We carbon-dated burnt bones from a fireplace,” archaeologist Olof Ostlund at the Norrbottens museum said. The hunters would have been near the retreating ice sheet that was once 3 km (1.9 miles) thick.
Experts examined sediments that showed the camp was on the shore of the former giant lake, briefly isolated from the North Sea by land uplift in the south before breaking through again.
Lulea’s old town, with a 15th century church and bright red-painted wooden houses, was originally built on an island for safety when it was as an outpost of the then Swedish-Finnish Kingdom to counter Russian influence near the Arctic Circle. Now the village is high and dry, out of sight of the sea. Sheep graze on a field in what used to be the port. In one spot, Sweden’s coastline has risen about 300 metres since the Ice Age ended about 10,000 years ago.
The falling water level puzzled people for generations. Some Christians believed it was caused by still-receding waters after the Biblical story of Noah, who built an Ark to rescue the world’s animals from a god-sent flood.
Elsewhere in the world, many nations are worried by potential costs if sea levels rise in line with scenarios by the UN panel of climate scientists for a gain of 18 to 59 cm (7-24 inches) this century after 17 cm in the last century. The panel says that rising temperatures, caused by emissions of carbon dioxide from burning fossil fuels, are the cause.