booklet 10 - sea level change

• Eustatic changes in sea level

  changes in sea level that occur over the whole earth as a result of changes in seawater volume or ocean basin capacity and thermal expansion. Associated with periods of glaciation Can be short, medium and long term
• Isostatic changes in sea level

  localised sea level changes and movement of land caused by land rising and falling. Also caused by melting glaciers. Medium term
• Tectonic changes in sea level

  Can be global or local sea level change and caused by movement of tectonic plate - sudden uplifts, down thrusts as well as collision and spreading of plates. Rapid effect so short term
• tectonic uplift or down thrust

  short term
• Isostatic change


  medium term
• Continental separation and collision

  long term
• thermal expansion


  short/medium term
• Global warming and ice melting

  short/medium term
• isostatic readjustment


  Land that is covered in ice is getting slowly pushed down relative to se level. As ice melts from some land areas the land begins to rebound back to its previous position. This melting of ice causes the weight and pressure to be removed so the land rises and slowly recovers (isostatic recovery)
• Impact of isostatic readjustment on the UK

  Isostatic readjustment has had huge impacts on the coastlines of the UK. In the north, the land is rising for example in Scotland because of melting ice. The south however is sinking as a result of the melting ice. This process is causing emergent and submergent landforms to occur all over the uks coastlines.
• Sea level change in past 10,000 years

  At maximum, sea level was 130m lower than present day

  The sea level has been rising since 1930 due to global warming
• Implications of melting Antarctica ice on future sea level

  The melting of the Antarctica Ice will have huge implications.

  
  

  Sea levels will rise by large amounts causing flooding to be a much more common problem not just locally but globally. Islands and communities like Kiribati will completely disappear. Food security will be an issue as farmland will become salinized as well displacement of coastal wetlands. Entire ecosystems may be lost. More extreme weather like storm surges will be more common
• What is thermal expansion

  Top layer of water is getting warmer so ice caps are melting, this causes eustatic sea level rise
• Example of changes in relative sea level and land with tectonic activity

  TONHUKU earthquake - this effected over 200 meters of eastern coastline of Honshu and it dropped 0.6 meters in 2011

  Boxing day earthquake - 1600km fault line slipping, the sea bed rose by several meters and it reduced what the Indian ocean can hold
• ways in which oceans volume is increasing

  - due to melting ice from glaciers and ice sheets

  - due to thermal expansion - as water warms it changes volume
• unpredictability of sea level rise is due too...

  - not knowing what co2 emissions are going to be and how much warming will increase

  - we don't know how ice sheets are going to respond
• What is the range in prediction of sea levbel rise

  predictions vary from 18cm to 59cm between 1990 and 2090
• Impacts of sea level rise in the uk

  - entire ecosystems are at risk

  - tourism and recreation at risk

  - farmland is inundated with water so food security is impacted

  - 60% of the population at major risk

  - The east and south east of England are most at risk

  - services like schools, hospitals would be threatened
• Kiribati case study


  Kiribati is made of 33 atolls and is located in the Pacific

  It is under threat as the Pacific is the region most at risk, sea levels are rising up to 4m and 100% of the population live within 1km of coast. IN 50 years Kiribati will be underwater

  impacts -

  21000 people will have 1m or more of water

  people are having to relocate inland and relocate to land in Fiji

  risk of flooding and saline inundation

  People don't want to move to due immense attachment to their home