3.4 Sea Level Change

Question 1

What are the two different types of sea level change?

Answer 1

eustatic

isostatic

Question 2

What is eustatic sea level change?

Answer 2

caused by the change in the volume of water in the sea, or by a change in the shape of the ocean basins

Question 3

Are the effects of eustatic change local or global?

Answer 3

global

Question 4

What are the main causes of eustatic change?

Answer 4

1. changes in climate
   increase in temperature causes melting of ice sheets, which increase sea level, water expands which increases sea level further
   decrease in temperature causes more precipitation to fall as snow, the volume of water stored in glaciers and decreases the sea level
2. tectonic movements of the earth’s crust that alter the shape of ocean basins, sea floor spreading increases the volume of the basin and so decreases the sea level

Question 5

What is isostatic sea level change?

Answer 5

caused by vertical movements of land relative to the sea.
downward movement of the land causes sea level to rise locally
uplift of land causes sea level to fall

Question 6

Are the effects of isostatic change global or local?

Answer 6

local

Question 7

What are the main causes of isostatic change?

Answer 7

1. uplift or depression of the earths crust due to accumulation or melting of ice sheets, slow uplift of land can continue for thousands of years after the weight of a glacier has gone, accumulation of sediment can cause depression
2. subsidence of land due to shrinkage after abstraction of groundwater
3. tectonic processes, one plate is forced under another

Question 8

Why does sea level vary on a short time scale?

Answer 8

due to tidal cycles, onshore winds, low atmospheric pressure systems
temporary rise

Question 9

Describe the previous sea levels through time

Answer 9

1. last glacial period, water was stored in ice sheets so sea level was lower - 130m than present
2. temperatures started to increase, ice sheets melted and sea level rose
3. sea level has fluctuated since then
4. since 1930 sea level is rising

Question 10

How long ago was the last glacial period?

Answer 10

110,000 - 12,000 years ago

Question 11

What is the main cause of sea level rise?

Answer 11

climate change

Question 12

What is global warming?

Answer 12

when global temperature increases

Question 13

Why has the temperature increased rapidly over the last century?

Answer 13

due to human activities such as deforestation and during fossil fuels which cause climate change

Question 14

Why do human activities cause climate change?

Answer 14

increase the concentration of greenhouse gases in the atmosphere

Question 15

What do greenhouse gases do?

Answer 15

they absorb outgoing long-wave radiation so less is lost to space. as the concentration increases more energy is trapped and the plant warms up

Question 16

Why does climate change increase sea levels?

Answer 16

causes an increase in sea level due to the melting of ice sheets and thermal expansion of water in oceans

Question 17

How high is the global sea level rising per year?

Answer 17

2mm

Question 18

What is the predicted sea level rise per year going to be in 2100 if greenhouse gas emissions are still high?

Answer 18

8-16mm