sea level change

• what can cause short-term sea level change?

  high tide and low tide- a daily phenomena due to the gravitational pull of the moon

  wind strength and direction- these can change causing a change in sea level for a couple of minutes

  atmospheric pressure- the lower the pressure, the higher the sea levels
• isostatic - localised sea level change:

  • isostatic sea level change could be due to post-glacial adjustment (glaciers weigh down the land beneath, and so the land subsides until it melts)
  • for example, post-glacial adjustment for the UK after the Ice Age has caused Southern England to subside around 1mm per year and Scotland to rebound and increase around 1.5mm per year
  • tectonic activity such as earthquakes and volcanic eruptions may cause land subsidence, thus causing isostatic sea level increase
• eustatic rise- global sea level change:

  • eustatic rise is due to thermal expansion- water expands as it gets warmer, and so the volume of water increases, which as a result sea level increases
  • this is due to global warming
• predicting sea level change is very difficult because various factors could affect changes, and the cause still isn't very understood
• why do people move to coasts, despite the high flood risk?

  due to tourism, high-yield agricultural land or housing pressure

  coastalisation is the movement of people towards the coast

  coastalisation can increase the environmental vulnerability of these locals to flooding due to storm surges
• when does a storm surge occur?

  when there is a short-term change in sea level, which may be due to low pressure during a depression or tropical cyclone
• how can a storm surge be exacerbated?

  through subsidence of the land- through tectonic activity or post-glacial adjustment

  by removing natural vegetation- mangrove forests are the most productive and complex ecosystem in the world. mangroves also provide protection against extreme weather events like cyclones which are very common in the Bay of Bengal.

  due to global warming
• How does global warming exacerbate storm surges?

  as the surface of the ocean gets warmer, it's estimated that the frequency and intensity of storms will increase, and so the severity of storm surges and flooding is also expected to increase
• why are mangroves destroyed?

  due to pressure for land space

  for tourism, local industry or housing
• consequences of sea level change for communities?

  some areas of the coast may have significantly reduced house and land prices as the area becomes known to be at significant risk

  this can lead to economic loss for homeowners and local coastal economies

  in the UK, many insurers don't provide home insurance to people living along coastlines that are at extreme risk of erosion or storm surges
• how do storm surges damage the environment?

  they destroy plant successions and damage many coastal landforms

  depositional landforms are most likely to be destroyed due to their unconsolidated nature
• environmental refugees:

  • globally, more than 1 billion people live on coasts that are at risk from coastal flooding and 50% of the world's population currently live within 200km of the coast
• • as storm surges and erosion along some coastlines are predicted to increase, so too is the volume of environmental refugees displaced internally or internationally
  • people may lose their homes, way of life, and culture as they are forced to migrate to avoid the rising eustatic sea level and the rising risk of coastal flooding