Sea level change

• What is the definition of sea level?


  Sea level is the boundary between land and sea.
• What is the daily range of tides?


  Daily tides range by a few metres.
• What characterizes the Quaternary period in terms of sea levels?


  The Quaternary period features alternating glacial periods with falling sea levels and inter-glacial periods with rising sea levels.
• What is eustatic change?


  Eustatic change is when sea level rises or falls by itself.
• What is isostatic change?


  Isostatic change is when land rises or falls relative to the sea.
• How does eustatic change differ from isostatic change?


  Eustatic change is global, while isostatic change is local.
• What happens to sea levels during cold glacial periods?


  During cold glacial periods, precipitation forms ice sheets which store water, causing sea levels to fall.
• What occurs at the end of glacial periods regarding ice sheets?


  At the end of glacial periods, ice sheets melt and retreat, causing stored water to flow into seas and sea levels to rise.
• What is isostatic subsidence?


  Isostatic subsidence is when the weight of ice sheets causes the land to sink during glacial periods.
• What happens during isostatic recovery?


  During isostatic recovery, the melting of ice reduces weight, causing the land to rise.
• What are the isostatic changes occurring in the UK?


  • Scotland is rising due to past ice sheets.
  • Most of south-east England is sinking due to sediment weight.
  • South of England is at risk of floods from isostatic change and sea level rise.
• How much is Scotland rising due to isostatic change?


  Scotland is rising at rates of over 2 metres.
• How much is south-east England falling due to isostatic change?


  South-east England is falling by 2 metres.
• What has been the overall trend in sea level change over the last 24,000 years?


  The overall trend is that sea levels have been rising, with an increase of 120 metres since the last glacial period.
• What has contributed to the gradual increase in sea levels since 8000 years ago?


  The gradual increase in sea levels since 8000 years ago is mainly attributed to climate change and global warming.
• What significant event occurred on Boxing Day 2004?


  A 9.0 to 9.3 magnitude earthquake caused a tsunami in the Indian Ocean.
• What was the impact of the 2004 earthquake on Banda Aceh?


  The earthquake caused 15m high waves that flooded Banda Aceh, sinking land and permanently flooding parts of the city.
• How did the earthquake affect the seabed and water displacement?


  The earthquake caused the seabed to rise, displacing $30 \text{ km}^3$ of water, which triggered the tsunami.
• What is the principle illustrated by the damage caused by tectonic activity?


  The principle is that change in natural systems involves high-magnitude low-frequency events.
• What are the landforms caused by changing sea levels?

  • Emergent coastlines: fall in sea level
  • Submergent coastlines: rise in sea level
• What are emergent coastal landforms?


  • Raised wave-cut platforms and beaches
  • Raised beaches common in Scotland
  • Example: Isle of Arran
• What are submergent coastal landforms?


  • Rias: sheltered winding inlets, common in south-west England (e.g., Kingsbridge estuary)
  • Fjords: formed by flooding deep glacial troughs, found in Norway, Chile, New Zealand
  • Dalmatian coastlines: ridges and valleys parallel to the coast, best example in Croatia
• What does the IPCC say about sea levels over the last 3000 years?


  The IPCC states that sea levels stabilized 3000 years ago.
• What was the average sea level rise from the late 19th to late 20th century?


  The average sea level rise was 1.7 mm per year.
• What was the average sea level rise from 1993 to 2010?


  The average sea level rise was 3.4 mm per year.
• What does the IPCC estimate for sea level rise by 2100?


  The IPCC estimates sea level could rise between 30 cm and 1 m by 2100.
• What causes sea level rise according to the IPCC?


  Sea level rise is caused by thermal expansion of water due to melting and heating of freshwater ice, like in Antarctica.
• What is the impact of climate change on Kiribati?


  • 33 low-lying islands in the Pacific Ocean.
  • Many islands could disappear in the next 50 years due to rising sea levels (1.2 cm/year).
  • 2014: President purchased land in Fiji for agriculture.
  • Government launched a migration policy for jobs in New Zealand and neighboring countries.
• How much above sea level are some islands in Kiribati?


  Some islands are only 1 metre above sea level.
• What is the rate of sea level rise in Kiribati compared to the global average?


  Sea levels in Kiribati are rising by 1.2 cm a year, which is 4 times more than the global average.
• What measures has the Kiribati government taken to address climate change impacts?


  The Kiribati government has launched a migration policy allowing people to apply for jobs in New Zealand and other neighboring countries.