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Climate Change - Sea Level Rise Impact

 

Future Sea Level Rise in Orkney

Orkney Sustainable Energy was established in 1995 to design, develop and operate wind energy projects, and by producing renewable energy, we hope to provide an alternative to using fossil fuels for our energy supply. The use of fossil fuels results in the emission of carbon dioxide, and the continuing influx of CO2 into the atmosphere is having an increasing impact, with climate change and global warming two major consequences. One of the more significant impacts is sea level rise, however because the magnitude of change appears small, sea level rise has not yet been fully recognised.

To give an understanding of the risk and impact of sea level change, a model has been developed that uses Ordnance Survey data to show how the coastlines of Orkney will change over the coming years. Orkney will be strongly affected by sea level changes, due to the scattered nature of the archipelago, and with many low lying islands there is the risk that some islands will be submerged. There is also the strong likelihood that new islands will be created in the quite near future, with rising seas cutting through the low-lying land that link the islands.

The model considers predicted coastline changes over the next 5000 years, and use a rate of change of 1.1m relative sea rise per hundred years. This is made up of 1cm per annum sea rise caused by thermal expansion of the seawater along with melting of the Greenland and Antarctic ice sheets, combined with 1mm per annum fall in the Orkney landmass; this is the consequence of isostatic changes following the last ice age. It can be seen that by the middle of the current century at least three new Orkney islands will have been created – Deerness, South Walls and Rothiesholm. As the sea levels continue to rise it can also be seen that major changes will occur should the Greenland ice sheet fully melt. Based on the rate of sea change predicted by the IPCC, it can be seen that the Orkney Mainland will divide in two when the relative sea level rises 7m, in approximately 500 years’ time. This is a very short timescale, when it is considered how long people have lived in Orkney. A higher resolution assessment of the impact on the core of the Orkney World Heritage Site has also been completed, with the strong possibility that rising seas will destroy the Standing Stones of Stenness and will turn the Ring of Brodgar into an island.  It should be noted that this 7m sea level rise is significant as a raised beach has been found at this level on the north coast of Hoy; http://www.landforms.eu/orkney/sea level change.htm. Raised beaches provide evidence of higher sea levels, with the likelihood that the Hoy beach occurred during a warming period in the last ice age, and accordingly it's evident that Orkney has seen this degree of sea level rise in the past.

The assessment considers the continuing impact of sea level rise assuming that no efforts are made to stop climate change and global warming, until the Antarctic ice sheets melt in 5000 years time. This will result in sea level rise of around 60m and it can be seen that many of the Orkney north isles become fully inundated, leaving only the higher parts of Rousay, the West Mainland and Hoy. This is a very different picture of Orkney; however it does appear that at least there will be land remaining to live on. It should be noted that most of the major conurbations are at sea level and the major cities would become submerged if the ice sheets melt, leading to significant changes to society.

This prediction assumes that mankind makes no effort to reduce fossil fuel use, however it is to be hoped that changes will occur once the consequences of altering the climate have been fully recognised.

Richard Gauld

Orkney Sustainable Energy

9 October 2013

 


North isles sea level rise 

 

Orkney Mainland sea level rise 

 

Orkney World Heritage Site and the impact of rising sea level 

 

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