What is Sea-level change?
Sea level is the average height of the ocean surface between high and low tide.
What the factors of short term sea level changes?
- High and low tide alter local sea level.
- Atmospheric air pressure low = rise in sea level.
- Winds can push water towards coast.
What the factors of long-term sea level changes?
- Isostatic change: local rise/fall in LAND level.
-Eustatic change: global rise/fall in WATER level
What are storm surges?
Storm surge are short term rises in sea level caused by low air pressure.
What the factors of storm surges?
- Depressions in Mid latitudes e.g UK
- Tropical cyclones
What factors can make storm surges worse?
- Strong winds push waves so height increases
- High/spring tides occur.
What is the research done by IPCC?
Hint: Sea level changes statistics.
Sea levels rose by 3.2mm each year 1993-2010. If Greenland Ice Sheet melts, sea level could rise by 7m.
Maldives Case Study
- 340,000 population
- 1200 islands
- Highest island is 2.3m above sea level.
- If sea level rises by 50m, 77% of the land will be lost.
- Malé has a 3m sea wall & artificial island Hulhmalé which cost $32M
Bangladesh Case Study
Bangladesh’s Coast is very vulnerable to flooding for a numebr of reasons:
- Very low lying river delta (1-3m above sea level)
- Storm surges meet river discharge
- Intense rainfall from tropical cyclones
- Unconsolidated sediment
- Deforestation of mangroves
What is the examples of Isostatic Change?
- Accretion: the weight of sediment causes land to sink
- Tectonic Uplift: movement of tectonic plates may cause land to rise.
- Isostatic Rebound: (post-glacial isostatic adjustment) after an ice age, glaciers will melt so land rises.
What are the example of Eustatic change?
- Global Warming: when the ice caps melt, this extra water will flow into the oceans and raise sea level.
- Global Cooling: water will be locked up in ice caps/glaciers, so sea level will lower.
- Thermal Expansion: if temperature rises, water will expand, which makes sea level rise.
What is the Greenhouse effect?
- This is a natural process that helps maintain a global temperature at 15°C
- Around 30% of Sun’s radiation is reflected back into space.
- The rest is absorbed or re-emitted by the Earth.
What is the Ice Age?
- The last Ice Age was 16,000 years ago
- North-West UK was covered in km^2 of ice, causing the land to subside
- In South UK, the land rose to balance this.
- As Ice melted around 10,00 years in Scotland the South-East is now sinking.
What are the case studies of tectonic activity
In terms of coasts.
- Tectonically active regions (New Zealand) experience uplift as fold mountains are formed.
- 1964 Alaskan Earthquake caused major changes to the coastline.
What are flood risk?
Places that are higher risk; are low lying coasts.
What are the factors of people that inhabit vulnerable coasts?
- They are popular with tourists
- Deltas & esturaries are good for trading with upriver places
- Deltas are fertile & ideal for farming.
What are the factors of erosional rate?
- Long fetch & destructive waves
- Structural weaknesses in cliffs
- Cliffs that are vulnerable to mass movement & weathering.
- Strong longshore drift
- It can also be increased by HUMAN activity such as offshore dredging.
What are Emergent Coastlines?
- Created when sea level FALLS
- Often have rocky coastlines with cliffs and flat raised platforms.
What is a raised beach?
Wave cut platform higher than current sea level, not reachable by high tide.
Examples: West Coast of USA
What is fossil cliffs?
Found behind raised beaches, have wave-cut notches & arches.
West Scotland - Isle of Arran
What are submergent coastlines?
- Created when sea level rises and floods the land
- Often by river valleys or glacially-carved valleys.
What is a Ria?
A river valley flooded with sea water, have a V-shaped cross section, common periglacial areas
eg South England
What are Fjords?
A glacial valley flood with seawater, have U-shaped croos section, common in glaciated areas
eg West Norway
What is a Dalmatian Coastline?
Formed where valleys lie parallel to each other and are flooded so only the tops are visible, making them look like islands.
eg Dalmatian Coast, Croatia
