The Ocean

Question 1

What is the vertical structure of the ocean?

Answer 1

Mixed/surface layer

• stirred by wind - constant temp and salinity
• varies between 10-200 m deep
• Depth and temp depends on heat flux and turbulence

Thermocline/Intermediate ocean layer

• rapidly decreasing temperature, part seasonal, part permanent
• around 200-2000m

Deep ocean

• low temp
• litte to no sunlight

Question 2

What is the primary productivity in the ocean?

Answer 2

The primary productivity is the fixation of carbon by photosynthesis. This is primarily done by plankton. These photosynthesising organisms need sunlight so they are found in the top 20-100m

Need:

• sunlight
• CO2 (dissolved CO2 (aq) inorganic carbon)
• Nutrients (N, P, Fe)

Limits to productivity:

• temp 0-40 C
• nutrient availability

Question 3

Which are the ocean circulation drivers?

Answer 3

Surface - wind driven
Deep - thermohaline (temp and salinity)
Meridional Overturning Circulation

Question 4

Why is ocean circulation important?

Answer 4

• Nutrient availability for primary production
• Uptake of C emissions
• Storing and redistributing heat (eg gulf stream towards poles)

Question 5

How is the heat exchange between atmosphere and ocean?

Answer 5

1. Shortwave radiation from the sun: Q_SW
2. Radioactive heat (IR) exchange between atmosphere and ocean: Q_LW
3. Sensible heat exchange between ocean and atmosphere through conduction (temp difference w. winds): Q_S
4. Latent heat lost from ocean to atmosphere as water evaporates: Q_L
5. Advection, ie heat moved by currents: Q_V

Q ocean heat gain or loss:
Q = Q_SW + Q_LW + Q_S + Q_L + Q_V

Question 6

What are things that move water, create circulation?

Answer 6

Winds, tides, sun, gravity, density difference (temp and salinity), earths circulation, topography, (things in the water but very small impact)

Question 7

What circulation patterns are there?

Answer 7

Surface = wind driven

• top 400m
• dominated by average wind fields/patterns
• great gyres driven by wind

Deep ocean circulation = thermohaline

• subsurface currents
• driven by density differences = thermohaline (temp and salinity) circulaiton
• generallu very slow: from sinking to returning to surface ≈ hundreds of years
• dominant flow of water in the ocean

Question 8

How are the oceans changing?

Answer 8

• sea surface temperature
• changing salinity - eg melting ice caps/glaciers, evaportaion
• carbon uptake
• sea level rise
• acidification
• eutrophication

this could all have an impact on ocean circulation as well

Question 9

TF: what are two main components of the global ocean circulation? What are typically described as the dominant drivers for these?

Answer 9

Redistributing heat - drivers: wind and tides

Uptake of CO2 - drivers: thermohaline

Question 10

TF: The meridional overturning circulation is partly driven by dense water sinking deeper into the ocean. Where on the globe does this sinking occur? Describe briefly a factor/process that controibute to the sinking of water.

Answer 10

It occurs 400m under the ocean

Contributing to the sinking of water is the thermohaline. It is density defferences due to varying temperatures and salinity causing the water to sink, gravity playing its part as well.