Polar Oceans & Sea Level Rise

Question 1

Real tides

Answer 1

Dynamoc theory of tides further explains the details of the tides on Earth
Observed tidal range is much greater (on average ~2m) than max predicted lunar + solar tide (79 cm)

Question 2

Can the tide keep up with the forcing? No…

Answer 2

1) pesky continents in the way
2) even without that, there are wave speed issues
“shallow water wave speed” comapred to speed with which earth’s rotation sweeps you past the tidal bumps

Question 3

Bay of Fundy

Answer 3

world’s largest tidal range
max tidal range of 17m due to amplification

Question 3

Where is the excess heat from climate change going?

Answer 3

Mainly the ocean

Question 4

Impacts of climate change on ocean

Answer 4

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Question 5

What is sea level and how is it measured?

Answer 5

• Elevation where the sea surface meets the land
• Can be measured relative to a position fixed on land (i.e tide gauge) or measured by satellite (since 1933)

Question 6

Ways to measure sea level

Answer 6

• land-based tide gauges
• satellite altimetry (measuring height)

Question 7

Global mean sea level change

Answer 7

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Question 8

Global sea level changes due to

Answer 8

1. changes in mass of ocean (adding ice/water from land to ocean)
2. changes in density of ocean (ocean warming)
3. relative sea level also affected by: changes in land elevation & gravity field

1 & 2 are eustatic = worldwide change of sea level
3 is isostatic = changed in local elevation of land

Question 9

Melting land ice

Question 10

Types of ice

Answer 10

• ice sheets & glaciers: grounded ice on land
• ice shelves: floating extensions of glaciers
• icebergs: calve from glaciers & ice shelves
• sea ice: floating ice that froms from freezing seawater

Question 11

Why doesn’t sea ice cause sea level rise?

Answer 11

when the ice melts it still takes up the same volume

Question 12

Role of ice in earth system & climate

Answer 12

Sea ice:
- albedo feedbacks
- insulation between ocean & atmosphere (limiting heat, momentum transfer)
- deep water formation & global overturning circulation

Glaciers & ice sheets:
- sea level rise
- (potentially) deep water foramtion & global overturning circulation

Question 13

Where is earth’s water?

Answer 13

• vast majority in ocean
• 2.5% freshwater majority glaciers and ice caps

Question 14

Types of glacial systems

Answer 14

terms for glacier, ice cap, ice sheet

Question 15

Large cause of sea level rise

Answer 15

Mass loss from glaciers and ice sheets

Question 16

How much would sea level rise if all of Greenland and Antarctica ice sheet & glaciers melted?

Answer 16

surface area of ocean = surface area of earth * 0.71
volume of melted ice / surface area of ocean = sea level change

Question 17

Sea level change since last ice age

Answer 17

sea level in the past can be determined by paleproxies, inclduing the depth of old coral reefs

Question 18

Past ice sheets during glacial periods

Answer 18

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Question 19

Meltwater Pulse 1

Answer 19

fastest sea level rise, 10-20 meters in <500 years

Question 20

What’s happening at the molecular level?

Answer 20

• molecules vibrate and move faster in a fluid and therefore take up more space
• somewhat analagous to the ideal gas law: PV = nRT
• water is nearly incompressible
• V proportional to T

Question 21

Links between

Answer 22

• warming of atmosphere & ocean drives mass loss from ice sheets
• mass loss from ice sheets raises sea level & alters ocean circulation

Question 23

warm waters (from subtropical Atlantic) reach Greenland’s glaciers & drive melting

Question 24

Land elevation & gravity

Answer 24

- contributes to relative sea level - isostatic equillibrium: - the ship is the lithosphere, water is the mantle, cargo us the great ice sheets

Question 25

Uplift and subsidence of land level - present day

Answer 25

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Question 26

Gravity field also changes when ice sheets grow or shrink

Answer 26

-greenland ice sheet shrinking - sea level rise near antarctica

Question 27

Combined effects

Answer 27

Ups and downs -ice sheets are so large that thier grvaity pulls water towards them - when they melt this attration is lost, causing the sea level around them to fall

Question 28

Abrupt tectonic change

Answer 28

- another cause of land-level change - between earthquakes: plates slide freely but at shallow depth they stick together and the overriding plate thickens - during earthquake: edge of overriding plate breaks free, springing upwards -

Question 29

Projections: sea level rise in the future depends on human behavior

Answer 29

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Question 30

Breaking down the contributions to future change

Answer 30

- ocean heat content - grenland ice sheet mass loss - antarctice ice sheet mass los - glacier mass loss

Question 31

How abnormal is the current rate of sea level rise?

Question 32

Impacts of sea level rise

Answer 32

- flood risk in boston - US property losses projected to increase by the end of the century - erosion rates will drastically increase

Question 33

Adaptation strategies for sea level rise

Answer 33

- protect - accomodate - retreat