Sea Level Lecture 1- Introduction to sea level, what is it and why should we care? Flashcards
How many people are estimated to live in coastal floodplains?
200 million
If Antarctic and Greenland Ice sheets were to melt how much would global sea levels rise by?
70m
How many damage is Hurricande Katrina estimated to have made?
$96 billion
How many died in 2004 Indian ocean tsunami?
Quater of a million
What did the 1953 North Sea storm lead to?
Thames barrage
What time scale do waves happen across?
Seconds
What time scale do tides happen across?
hours, days, weeks, months, years
What time scale does weather happen across?
hours, days, weeks, months and years
What time scale does glacio-eustacy happen across?
Years to millennia
Name 4 causes of sea-level changes?
Waves, tides, weather and glacio-eustacy
What is MSL?
Mean sea level
What is mean sea level?
Arithmetic mean of hourly tides
What is mean tide level?
The sea level halfway between the mean levels of high and low water
What are tides?
Astronomical-gravitational influence of the moon and sun
What cycles do tides happen on?
Dirunal and semi-siurnal cycles
What are spring tides?
Moon and sun aligned
Higher highs and lower lows
What are neap tides?
Sun and moon out of phase
Lower highs and higher lows
How many low tides and high tides do most coastal areas experience every 24 h?
2 high and 2 low
What do tidal bulges represent?
High tides
What causes tidal bulges?
Greater or less gravity than the centre of the earth
What is microtidal spring tide range?
<2m
What is mesotidal spring tide range?
2-4m
What is macrotidal spring tide range?
> 4m
Where do some of the largest tides occur?
Bay of Fundy
How can we measure tides?
Tide gauges and satellite records
What does GRACE stand for?
Gravity recovery and climate experiment
What is diurnal tide pattern?
One high tide and one high tide per day - least common
What is semi diurnal tide pattern?
2 high and 2 low per day - most common
What is mixed tide pattern?
2 high and 2 low per day but at different magnitudes throughout the day
What can cause large tidal ranges?
Geomorphology
where are tide gauges mounted?
Harbours
Can anthropogenic influences be seen within tidal gauges?
Yes
What is the bias related to tidal gauges?
More in NH than SH despite more ocean in SH.
Led to overestimation in sea level change.
Do satellite records look at whole ocean?
yes
What is satellite altimeter?
Speed to beam to reach bottom of ocean
Very accurate
How does GRACE work?
Gravity
Used more for ice sheet change
Two satellites measuring distance
Connected by radiation
Is sea level change linear?
No - it fluctuates
What is RSL?
Relative sea level
What could RSL rise be due to?
Land sinking
Ocean level rising
Some combination
What could RSL fall be due to?
Land rising
Ocean level falling
Some combination
What is RSL a combination of?
What oceans and land are doing
What are complex causes of RSL?
Ocean density changes
Ocean-atmospheric interaction
terrestrial water storage
Ice melting
Ocean circulation
Vertical land motion
Have all sites along any coastline experienced the same sea level history?
No due to variations in how wayer added to the oceans is distributed across the planet and differing land movements and so term RSL is used.
