Sea-Level Change Part 1

Question 1

What is Sea-Level?

Answer 1

Average level of the ocean’s surface. Snapshot or a moment in time. Elevation at a particular point in time.

Question 2

What is Relative Sea-Level?

Answer 2

observed change in water level at a particular point (relative to the level of the nearby land)

Relative SL is what you experience.

Question 3

What drives Relative Sea Level?

Answer 3

1. Isostacy
2. Gravity effects
3. Tectonics
4. Subsidence
5. Sea Surface Temperature differences
6. Meteorological forcing
7. Ocean currents

Question 4

What is Eustatic Sea Level?

Answer 4

alteration to the global sea levels due to change in either the volume of water in the world oceans or net changes in the volume of the ocean basins.

• The big picture
• It is impossible to measure directly

Question 5

How much does global sea level change per year?

Answer 5

3.3 mm per year

Question 6

How much does VA and Mississippi sea level change per Year?

Answer 6

Mississippi - ~11mm/yr
VA - ~5mm/r

Question 7

What are the drivers of Ecstatic Sea Level: volume of water?

Answer 7

1. Changes in total ocean water mass
2. Changes in the size of the ocean basin
3. Density changes of the water (thermal expansion)

Question 8

How is water added to the system?

Answer 8

Through Volcanism (Think of BLAG and Uplift Weather Hypothesis)

Question 9

How does vulcanism add water?

Answer 9

o Release of CO2 in the atmosphere from mid ocean ridges and subduction zones.
o This drives up the temperatures, melts ice, and puts more water into the ocean driving up sea level.
o Also has a release of volcanic water vapor. This transports water from the mantle and asthenosphere into the active system over time (active water cycle).

Question 10

How do you get rid of water?

Answer 10

Suductuion

Question 11

How much of the mantle is made up of water?

Answer 11

6%

Question 12

How much water is subducted?

Answer 12

~7%

Question 13

What are some active water reservoirs?

Answer 13

o Atmosphere (water vapor)
o Ice (mountain glaciers, ice sheets, NOT sea ice)
o Lakes, River, ground water
o Human influences: dams, water use, etc

Question 14

How have paper mills in Hampton Roads played a role in increasing relative sea level?

Answer 14

In our area, papermills extract ground water directly and once through the system, are directly deposited into the water body. This contributes directly to sea level rise.)

Question 15

Steric effects

Answer 15

how expanded or contracted that water is. As the heat in the atmosphere gets circulated into the ocean (through ocean circulation), right down to the bottom water, heat then expands the deep oceans the entire warms. For every one degree it does so, global sea level goes up by 80cm.

Question 16

What are the drivers of Eustatic Sea Level Change: Ocean Reservoir Size?

Answer 16

1. 1. Position of continents & extent of mountain ranges
2. Changes in spreading rates
3. Changes in crustal/lithosphere thickness
4. Isostatic Loads
5. Sedimentation

Question 17

Describe the Position of continents & the extent of mountain ranges as a driver of Eustatic Sea Level Change: Ocean Reservoir Size?

Answer 17

• As continents shift and reorient themselves, they change the shape of the oceans, the relative depth of the ocean basin, change how much ocean and how many continents.
• If the Wilson Cycle switches and continents crash back into each other, large mountain ranges will be created. Land masses that take up so much room, more land at higher elevation and less surface area. Ratio of continent to ocean changes. Sea level falls (Himalayas)

Question 18

Describe the Changes in spreading rates as a driver of Eustatic Sea Level Change: Ocean Reservoir Size?

Answer 18

• As continents shift and reorient themselves, they change the shape of the oceans, the relative depth of the ocean basin, change how much ocean and how many continents.
• If the Wilson Cycle switches and continents crash back into each other, large mountain ranges will be created. Land masses that take up so much room, more land at higher elevation and less surface area. Ratio of continent to ocean changes. Sea level falls (Himalayas)

Question 19

Describe the Changes in spreading rates as a driver of Eustatic Sea Level Change: Ocean Reservoir Size?

Answer 19

• As continents shift and reorient themselves, they change the shape of the oceans, the relative depth of the ocean basin, change how much ocean and how many continents.
• If the Wilson Cycle switches and continents crash back into each other, large mountain ranges will be created. Land masses that take up so much room, more land at higher elevation and less surface area. Ratio of continent to ocean changes. Sea level falls (Himalayas)

Question 20

Describe the Changes in spreading rates as a driver of Eustatic Sea Level Change: Ocean Reservoir Size?

Answer 20

• As continents shift and reorient themselves, they change the shape of the oceans, the relative depth of the ocean basin, change how much ocean and how many continents.
• If the Wilson Cycle switches and continents crash back into each other, large mountain ranges will be created. Land masses that take up so much room, more land at higher elevation and less surface area. Ratio of continent to ocean changes. Sea level falls (Himalayas)

Question 21

Describe the Sedimentation (filling accommodation) as a driver of Eustatic Sea Level Change: Ocean Reservoir Size?

Answer 21

• As continents shift and reorient themselves, they change the shape of the oceans, the relative depth of the ocean basin, change how much ocean and how many continents.
• If the Wilson Cycle switches and continents crash back into each other, large mountain ranges will be created. Land masses that take up so much room, more land at higher elevation and less surface area. Ratio of continent to ocean changes. Sea level falls (Himalayas)

Question 22

What is causes the supercycles in sea level?

Answer 22

combination of how much water is there, how hot is that water, and how big is the basin to hold it

Question 23

Describe why BLAG is related to Eustatic Sea-Level?

Answer 23

There are direct and indirect linkages between the same things driving cooling on earth are also causing sea levels to fall. From Blag (sea floor spreading slows through time, creating more space for water so global sea level will fall).