12.1: What are the main characteristics of Oceans?

Question 1

What percentage of Earth’s surface do oceans and seas cover?

Answer 1

Oceans and seas make up about 71 percent of the Earth’s surface.

Question 2

What are the five major individual oceans?

Answer 2

The five major individual oceans are the Pacific, Atlantic, Indian, Southern, and Arctic Oceans.

Question 3

What is the average width of the continental shelf?

Answer 3

The average width of the continental shelf is 70 km.

Question 4

What is the slope angle of the continental shelf?

Answer 4

The slope angle of the continental shelf is just under 2 metres per kilometre.

Question 5

What is the abyssal plain?

Answer 5

The abyssal plain is the deepest part of the oceans.

Question 6

What are seamounts?

Answer 6

Seamounts are underwater mountains that can rise over 3000 m above the abyssal plain.

Tend to be a result of tectonic activity- ocean ridge. Can also form at volcanic hotspots eg. Hawaii

Question 7

What are guyots?

Answer 7

Guyots are seamounts that were once above sea level but have eroded and sunk below it.

Tend to be a result of tectonic activity- ocean ridge. Can also form at volcanic hotspots eg. Hawaii

Question 8

What is the significance of mid-oceanic ridges?

Answer 8

Mid-oceanic ridges are divergent plate boundaries and are chains of basaltic mountains.

Question 9

What is the thermocline?

Answer 9

The thermocline is the rapid change in temperature with depth in the ocean.

Question 10

What is salinity?

Answer 10

Salinity is a measure of the concentration of sodium chloride in water, expressed in parts per thousand (ppt).

Question 11

What is the average salinity of seawater?

Answer 11

The average salinity of seawater is about 35 ppt.

Question 12

How does temperature affect water density?

Answer 12

High salinity makes water denser, while high temperature makes it less dense.

Question 13

What is the role of phytoplankton in the ocean ecosystem?

Answer 13

Phytoplankton are vital to the marine food web as they supply nearly all the energy and nutrients.

Question 14

What is the photic zone?

Answer 14

The photic zone is the layer of water where there is enough light for photosynthesis to occur.

Question 15

What is thermohaline circulation?

Answer 15

Thermohaline circulation is the deep ocean currents driven by differences in temperature and salinity.

Question 16

What is the Gulf Stream?

Answer 16

The Gulf Stream is a warm saline current that flows from the coast of Florida to the northeast.

Question 17

What happens to water in the North Atlantic as it cools?

Answer 17

As the water cools, it increases in density and sinks, contributing to deep-water currents.

Question 18

What are hydrothermal vents?

Answer 18

Hydrothermal vents are hot water springs on the ocean floor that support unique ecosystems.

Question 19

What is the primary source of energy for ocean organisms?

Answer 19

All organisms need a source of energy to live, primarily derived from the Sun.

Question 20

What are cold seeps?

Answer 20

Cold seeps are low-temperature flows of water that support communities dependent on chemical energy.

Question 21

How do organisms at cold seeps obtain energy?

Answer 21

Organisms at cold seeps obtain their energy from hydrocarbons such as methane or hydrogen sulphide.

Question 22

What are the key oceanic producers?

Answer 22

Phytoplankton are the key oceanic producers.

Question 23

What is net primary productivity (NPP)?

Answer 23

NPP is a measure of how much of the Sun’s energy is captured, usually measured as grams of carbon per unit of area per year.

Question 24

What is the total annual NPP in the oceans?

Answer 24

Total annual NPP is approximately 100 billion tonnes of carbon, with just under half occurring in the oceans.

Question 25

What factors influence NPP in ocean ecosystems?

Answer 25

Nutrient inputs, particularly nitrogen, influence NPP.

Question 26

Where does the highest productivity per unit of volume occur in the oceans?

Answer 26

The highest productivity occurs in locations with the greatest supply of dissolved nutrients, such as coastal regions.

Question 27

What are sub-tropical gyres described as?

Answer 27

Sub-tropical gyres are described as biological deserts due to their lack of dissolved nutrients.

Question 28

What is the Antarctic marine ecosystem known for?

Answer 28

The Antarctic marine ecosystem is known for its high productivity despite low temperatures.

Question 29

How does sea ice formation affect nutrient availability in Antarctica?

Answer 29

As sea ice forms, saline water becomes dense and sinks, allowing less salty deep water to upwell and carry nutrients.

Question 30

What is a significant food source in the Southern Ocean?

Answer 30

Squid are a significant food source, feeding on primary consumers like zooplankton and krill.

Question 31

What influences the ecosystem in Antarctica?

Answer 31

Seasonal changes in the extent of sea ice greatly influence the ecosystem.

Question 32

What are salt marshes?

Answer 32

Salt marshes are coastal wetlands where the ocean meets the land, common in mid to high latitudes.

Question 33

How do sediment and tides affect salt marshes?

Answer 33

Accumulation of sediment and the rhythm of tides are crucial for salt marsh development and productivity.

Question 34

What is plant succession in salt marshes?

Answer 34

Plant succession is the change in vegetation zones from low tide to high tide areas, influencing other organisms.

Question 35

What happens to salinity when the amount of water in the oceans changes?

Answer 35

When the amount of water increases, salinity decreases (water becomes more dilute). When the amount of water decreases, salinity increases.

Question 36

What is the halocline?

Answer 36

The halocline is a layer of water below the mixed surface layer where a rapid change in salinity can be measured as depth increases. Usually found between 250-700m.

Question 37

How does temperature affect salinity in tropical seas?

Answer 37

In tropical seas between 23°N & S, high temperatures create high evaporation rates, resulting in a very saline and warm surface layer.

Question 38

What is the thermocline?

Answer 38

The thermocline is the boundary between two layers where temperature changes abruptly. 90% of the ocean is found below the thermocline.

Question 39

What is the relationship between salinity and water density?

Answer 39

As salinity increases, so does density. Fresh water (low salinity) floats on top of salt water (high salinity).

Question 40

What are ocean currents?

Answer 40

Ocean currents carry energy from one place to another. Surface currents are driven by wind, while deep currents are influenced by temperature.

Surface currents carry warmer, less dense water from the equator to the poles. Warm water from surface currents replaces colder, denser water that sinks to the ocean floor.

Deep currents carry colder, denser water along the ocean floor from the poles to the equator. Water from deep currents rises to replace water leaving in surface currents.

Question 41

What occurs during upwelling?

Answer 41

Upwelling brings nutrient-rich water to the surface, occurring across less than 1% of the ocean’s surface.

Question 42

How do seasonal changes affect ocean temperature?

Answer 42

Between summer and winter, ocean temperature changes vary between 500-1000m, with a slower decline below this level.

Question 43

What is the effect of cold oxygen on carbon sinks?

Answer 43

Cold oxygen is more oxygen-rich, making it better for carbon sinks.

Question 44

How do atmospheric conditions affect ocean mixing?

Answer 44

In winter, higher winds and storms mix cold and warm water, while in summer, high pressure leads to calmer and more stable conditions.

Question 45

What is marine snow?

Answer 45

Dead organisms and organic material falling from the surface of the ocean to the ocean floor.

Question 46

What is the longest mountain range on earth?

Answer 46

Mid-Atlantic Ridge- 650,000km, 0-20 million years old.

Question 47

What are the features of the continental shelf?

Answer 47

Warmer and shallower water
Hurricanes and storm surges
Marine food comes from here

Question 48

What are factors that increase and decrease salinity?

Answer 48

Increase:
Evaporation:
- More outputs than inputs so less freshwater= increasing salinity, increases density which means that water is ‘heavier’ relative to the other water around and sinks.

• Freezing of sea water- rejection of salt.

Decrease:
- Precipitation
- Melting of glaciers or icebergs
- Groundwater and river flows into an ocean.

Question 49

What are the seasonal variations for salinity?

Answer 49

• More sun in summer= more evaporation- increase in salinity.
• Greenland’s glaciers melt in summer- decreasing salinity:
  1. Temperature rise
  2. Melting of icebergs
  3. Release of freshwater
  4. Fall in salinity
• In winter there is an increase in rainfall- decrease in salinity.
• Low latitudes between the tropics- sea is warmer- sun rays are more concentrated.
• Colder at higher latitudes.

Question 50

What are the seasonal variations in temperature in the ocean?

Answer 50

In winter, currents, storm surges and increased rainfall- higher winds and storms- mix the water so the cold and warm water mix more.
In summer, there is high pressure and it is more calm and stable.

Decrease in temp:
- More inputs than outputs, increased density, downwelling, water sinks and is heavy.

Increase in temp:
- More evaporation= more outputs than inputs, density decreases, water rises and is ‘lighter’.