Oceans

What is differential heating?

Due to curvature of the Earth, the solar radiation is more concentrated on the equator. ITCS

What is thermal expansion?

Due to warm water/currents being less dense, it expands and raises water levels. Accounts for 58% of sea water level rise

What % does thermal expansion cause a raise in sea water levels?

58%

Impact of Coriolis effect on ocean currents?

Deflects ocean surface currents to the right in the Northern Hemisphere and the left in the Southern Hemisphere. Creates gyres

What are gyres?

5 circular systems of ocean currents formed by global wind patterns, the Earth's rotation (Coriolis effect), and landmasses.

Example of a gyre

North Pacific Gyre

What is a continental shelf

Area of the continent (land mass) that extends into the ocean.

Characteristics of a continental shelf

Average water depth above the continental shelf is 60m. Makes up less than 10% of the oceans. Characterised by a continental slope that marks the end of the shelf and descends into an abyssal plain

What is a guyot?

An undersea mountain with a flattened top, more than 200m below the surface. Seamounts that were extended above sea level, wave erosion flattened the ridge

Characteristics of a guyot

Evidence of coral reefs. Marine snow or sediment can sometimes cover the Guyots and mostly found in the Pacific ocean

What is an abyssal plain?

An area of flat sea bed at depths of 3km to 6km and is adjacent to the continental slope

Characteristics of an Abyssal Plain?

Make up half of the Earth’s surface, largest and most common in the Atlantic Ocean

Largest abyssal plain?

North Atlantic, Sohm Plain that is 900,000km2

What is an ocean ridge?

Large underwater mountain ranges. Often found in the middle of oceans

What is an ocean rift

Steep sided notches where magma rises at a constructive plate boundary.

Characteristics of ocean ridges

Can find hydrothermal vents - not volcanoes. They are heated water and minerals.

Characteristics of ocean rifts

Plates are more apart as the new magma rises at the bottom of riff valleys.

Example of an ocean rift

Mid Atlantic Rift valley is only 15km wide in some places

What is an ocean trench?

Long narrow depressions on the sea floor, some of the deepest places on earth.

Characteristics of an ocean trench

Vary in depth but can be 7-11km long. Formed by subduction at a destructive plate boundary. Pressure is more than 1000 times that on the surface

Deepest oceanic trench

Challenger Deep, part of the Marina Trench

Depth of the Pacific Ocean

approx 4km

Depth of the Atlantic ocean

approx 3.5km

Artic ocean depth

1km

Depth of the Indian Ocean

3.7 to 3.9 km

What is the photic zone?

Layer of water where there is enough light for photosynthesis - light can penetrate

What is the aphotic zone?

Lacking in sunlight - absence of photosynthesis

What is bioluminescence

When organisms generate small amounts of light through a chemical reaction

What nutrients are hydrothermal vents rich in?

silica and methane

What is interesting about cold seeps and nutrients?

They are dependent on chemical rather than solar energy. Increased nutrients because it’s cold eg. Gulf of Mexico

Pattern of nutrient levels

Lower nutrient levels at the surface. Nutrients are used up immediately and trapped in biomass

What is krill

They are small shrimp-like crustacea that inhabit the upper parts of the water column and live about 5 years. They are primary consumers

Biomass of Krill

Their biomass is estimated at more than that of the human race. They exist in swarms.

% of marine NPP in coastal regions compared to deep ocean regions

20% in coastal regions compared to 80% in deep ocean regions

% of global NPP in coastal regions compared to deep ocean

10% global NPP in coastal regions compared to 40% in deep oceans

Where is the highest NPP in oceans

Volume occurs in locations where the supply of dissolved nutrients is greatest

Despite % total of marine NPP from coastal regions appearing limited…..

In relation to the area and depth of water, productivity is high

What is a pelagic ecosystem

Pelagic ecosystems refer to the oceanic environments that cover more than 70% of the Earth's surface

Estimated NPP in coastal regions

250/g/cm2/year

Estimated NPP in deep ocean regions

130g/cm2/year

Natural income of the ocean ecosystem

$6.9 trillion

Trigger level of Krill catch

620, 000 tonnes a year

Issue and next steps if the total allowable catch were to increase

Krill harvesting would need to be spread out across the whole region to avoid over-fishing in specific areas

How much of annual oil production was derived from the ocean?

37%

How much gas production occurs offshore

65 trillion cubic metres

Most productive areas for oil and gas

Gulf of Mexico because it is rich in hydrocarbons.

Where is the usual highest distribution of oil and gas

Edge of land masses

Example where gas exploration has occurred in deep waters

Cheyenne gas field in the Gulf of Mexico is at a depth of 2740m

How has oil and gas extraction led to increase in species

Rigs act as artificial reefs which has increased the Red Snapper in the Gulf of Mexico

How many jobs does oil and gas extraction produce

6 million direct jobs

What is the profit of oil and gas a day

$2.8 billion

Amount of jobs created in the Gulf of Mexico as a result of oil and gas extraction

240,000 direct jobs