Wednesday, September 17, 2014

New Nordic land rises from sea as climate change creeps in

December 1, 2012 by  
Filed under News, Science, World

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A Stone Age camp that used to be by the shore is now 200 km (125 miles) from the Baltic Sea.  Sheep graze on what was the seabed in the 15th century. And Sweden’s port of Lulea risks getting too shallow for ships.

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 United States.

The uplift of almost a centimeter (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 center 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.

SHALLOWER 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 meters 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 meters since the Ice Age ended about 10,000 years ago.

BIBLICAL FLOOD

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 U.N. 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.

The U.N. projection excludes the possibility of an acceleration of the melt of Greenland and Antarctica, because that is uncertain.

Even so, many experts expect a quickening thaw and say that sea levels could rise in total by a meter this century.

Almost 200 governments are meeting in Doha, Qatar, this week to try to revive a U.N.-led effort to slow climate change that is also projected to cause more floods, droughts, heatwaves and more powerful storms.

Professor David Vaughan, of the British Antarctic Survey, said sea levels will change at widely differing rates due to land uplift or subsidence, shifts in gravity and variations in ocean currents and winds such as in the Pacific Ocean.

Sea levels near Greenland, for instance, could fall because its ice sheet has a strong gravitational pull that raises the local sea level. If the ice thaws, the water level will sink.

“Scandinavia will be emerging … sea level around Antarctica and Greenland will be going down. Almost every projection I have seen shows the highest rates of rise will be in the equatorial Pacific,” he said.

Near Lulea, local resident Hans Lindberg, 56, looks out of the wooden seaside cabin that his parents built in 1960 towards what was then the island of Kalkholmen a few hundred meters (yards) away.

“We could look out from here and only see the sea,” he said, pointing to a muddy bank where reeds are growing and linking the island to the mainland. Residents of the former island say they fear the link may bring unwanted visitors — perhaps burglars.

“You can walk to the island now. When I was young my father had a heavy boat that we could pull through the shallow part of the channel. That’s now impossible,” he said.

As evidence of the change, he shows a faded album with a black and white photo of two young girls — his sister and cousin — playing in a sandpit in the 1960s by the cabin. It shows an open sea with no sign of the muddy causeway.

It was the 18th century Swedish scientist Anders Celsius, after whom the temperature scale is named, who first estimated the rate of land rise by studying 16th property documents that marked offshore rocks, valued by hunters, on which seals basked.

By Celsius’ time, many of the “seal rocks” were so high out of the water that the mammals could no longer climb onto them, according to a book by historian Martin Ekman. With the data, Celsius was the first to come up with a rough estimate of the fall — a slight overestimate of 1.4 cm a year.

Aware that rising global seas will reduce the local land rise, Bengten at Lulea municipality says rules due to take effect in 2012 will ban new homes less than 2 meters (6 ft 6 inches) above sea level after a recent building surge.

“It’s a fashion. Elderly people were never attracted to living close by the sea — they know how cold, how damp and windy it was. Perhaps it comes with better buildings,” she said.

Many places, from North Carolina to Australia, have struggled with sea level rise amid property developers’ fears that it could wipe billions of dollars off values if coastal areas are re-defined as flood zones.

“Up in the north where land is rising most…there won’t be any problems this century,” said Thomas Hammarklint of the Swedish Meteorological and Hydrological Institute, since land rise would cancel out sea rise of up to a meter.

But he said that Stockholm, for instance, and areas in south and western Sweden where land is rising less fast might suffer.

One drastic option would be for nations around the Baltic Sea, including Russia, Germany, Poland and the Baltic nations, to build barriers from Denmark to Sweden at the narrow mouth of the sea near Copenhagen, he said, declining to estimate costs.

“The Baltic Sea would be a lake again.”

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