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Climate change will raise the sea level in the Gulf of Finland
Posted on 5 May 2013 by John Hartz
The following article is a reprint of a news release posted by the Finnish Meteorological Institute on Apr 29, 2013
The Finnish Meteorological Institute has updated its estimates concerning the impact of rising sea levels on the Finnish coast.
Photo: Eija Vallinheimo
Post-glacial rebound and changes in the Earth’s gravity field protect the Finnish coast against rising sea levels, especially in the Gulf of Bothnia. In the Gulf of Finland, the sea level is starting to rise.
The rise in ocean levels varies regionally
Global warming raises ocean levels at an accelerating pace, currently on average about three millimetres per year. The reasons for this are the thermal expansion of sea water and the melting of glaciers. It is estimated that by the end of this century, ocean levels will rise at least about 20 centimetres. The highest estimates are nearly two metres.
There is, however, great regional variation in the rise, for reasons such as the uneven warming of seas, changes in the Earth’s gravity field, and changes in the circulation of seas. The Finnish Meteorological Institute has used the latest scientific publications to estimate the impact of these regional factors on the Finnish coast.
As glaciers melt, mass will shift from continents into seas. In consequence, the Earth’s gravity field and the height of the Earth’s crust will be altered. The mass of continental glaciers will no longer attract sea water as strongly as before. In addition, the Earth’s crust will rise under the lighter glacier. For this reason, the rise in the sea level will be minor near the melting glacier, whereas the rise will be felt more acutely further away from the glacier.In consequence, the melting of the continental glacier in Greenland will have a fairly small impact on the Finnish coast. The regional rise in Finland will remain below the global average.
The characteristics of the Baltic Sea affect the Finnish coast
In addition to the regional rise in ocean levels, local events in the Baltic Sea affect the sea level changes on the Finnish coast. In Finland, the uplift of the land after the last glacial period is still 4–10 millimetres per year. Moreover, climate models predict stronger western winds, which will push water into the Baltic Sea through the Danish straits and water will accumulate against the Finnish coast.
So far, post-glacial rebound has offset the rise in sea level in Finland, but the situation is gradually changing on the southern coast. It is estimated that the sea level will start to rise in the Gulf of Finland. In the Gulf of Bothnia, the uplift is still likely to even out the sea level rise in the coming decades.
If the highest projections come to pass, the sea level will rise everywhere on the Finnish coast: by as much as 90 centimetres in the Gulf of Finland by the end of the century, by 65 cm in the Bothnian Sea and by about 30 cm in the Bay of Bothnia.
The current estimate concerns the change in the average sea level in the long term. In addition, the impact of waves and other changes in the short-term variation of the sea level must be taken into account in building and other activities on the coast. In the near future, the Finnish Meteorological Institute will update its estimates of the lowest recommended building heights, where these factors will also be considered.
If the Gulf of Bothnia starts showing a rising trend too, that'd be a pretty big surprise.
English Wikipedia's article on the Baltic Sea has some interesting background on this topic, including a map showing about how much of Finland was submerged 11,000 years ago.
Why would you find a rising sea level trend there surprising? The region was squished down by the presence of the Fennoscandian ice sheet during the last ice age, and the land has been rising back up since then. The rate of glacial isostatic uplift slows over time, so a globally coherent melt of land-based ice (and consequent global sea level rise), such as today, will eventually overcome local factors.
It is an interesting fact that if the whole of the Greenland ice sheet melted, while average sea levels would rise by 7 metres, near Greenland the sea level would FALL by 100 metres! This is because the ice exerets a considerable gravitational force on the surrounding ocean.
http://www.youtube.com/watch?v=RhdY-ZezK7w
"There is, however, great regional variation in the rise, for reasons such as the uneven warming of seas,..."
I would have thought that uneven warming would not effect the regional sea level?
John Brookes@4,
You are correct. "uneven warming of seas" should be replaced by "isostatic rebound from last glacial maximum". This and "changes in the Earth’s gravity field" are the 2 mean SL variations we know. Of course we are considering long term, excluding short term noise such as tides and weather fluctuations. "Uneven warming" is part of the weather.
<pikaia> also considering the rotation of the earth, and the melt in the Antarctica, the highest rise should be equatorial so this estimate might not be too far off. (local housing infotainment) The lowest building limit currently for temporary residence buildings is (if I recall correctly) +2 m so there'll be a lot of ocean front cottages on sale in Finland in 2150, I guess. Currently their prices are way outside normal salary rates. Main reason of selling those to outsiders currently is testament disputes. In cities though, even residential buildings may sometimes be built this low. These might be pretty cheap after some heavy winter storm/harsh winter+fast spring (ending local infotainment)
oops, the equatorial argument might be wrong since it's projected that the high northern oceans would warm up the most relatively, thus the expansion of water would be higher in the northern hemisphere. but anyway the simple amount of ice melt = amount of sea level rise equation does not hold locally everywhere.
Just one more very OT thing. What is up with Tamino? No new blog posts for some time, and not taking comments...
<John Brookes> I think he said a few months back he's preparing a new book, so this may be related to that, real life hurries, that is.
Are there corresponding places where SLR is greater than expected from isostatic rebound? I seem to remember that some areas, such as the Missippi delta, are experiencing land lowering, due to isostatic rebound elsewhere on the crustal plate (one side of the dish is rising, the other side is falling). Such places would be subject to greater inundation, due to the double whammy of isostatic fall and SLR. Nasty combination, if I have my facts about right.
<pedantry>'Missippi'should be 'Mississippi'.</pedantry>
Sigh: old age has many pitfalls ... "8-/