1.b. The carbon and water cycles are systems with inputs, outputs and stores

Question 1

What are the stores of the water cycle

Answer 1

• water cycle consists of reservoirs where water is stored for variable lengths of time and the linkages of pathways between these reservoirs e.g. oceans, lakes, rivers
• oceans contain 97% of all waters. Fresh water comprises a tiny proportion of water in store and 3/4 is frozen in the ice caps of Antarctica and Greenland
• only a minute fraction of water is found in the atmosphere- explained by rapid flux of water in+out of atmosphere

Question 2

Inputs of the water cycle

Answer 2

• water vapour- evaporated from oceans, soils, lamkes and rivers and transpired through leaves of plants (evopotranspiration)
• moisture leaves atmosphere as precipitation/condensation. Ice sheets, glaciers and snowfiels release water by ablation

Question 3

Outputs of water cycle

Answer 3

• precipitation and meltwater drain from land surface as run off into rivers. Most rivers flow to oceans and soms drain to inland basins. Large part of water falling as precipitation on land reaches rivers only after infiltrating and flowing through soil
• after infiltrating soil, water under gravity may percolate into permeable rocks or aquifiers then reachers surface as springs

Question 4

Stores of carbon cycle

Answer 4

• consists of many stores/sinks connected by flows of carbon. Main stores are atmosphere, oceans, carbonate rocks, fossil fuels, plants and soils
• carbonate rocks e.g. chalk and deep ocean sediments are biggest carbon store. Carbon not stored in rocks and sediment found in oceans as dissolved CO2. Carbon stores in atmosphere, plants, soils relatively small

Question 5

Inputs of slow carbon cycle

Answer 5

• carbon stored in rocks, sea floor sedimnes and fossil fuels is locked away for millions of years. CO2 diffuses from atmosphere into oceans where marine organisms make their skells and skeletons by forming calcium carbonate. Organisms sink to sea floor and accumulate, over millions of years heat and pressure convert them to carbon rich sedimentary rocks
• residence time for carbon held in rocks is 150 million years. Some carbon rich sedimentary rocks are vented to the atmospehere in volcanic eruptions- others attacked by chemical weathering

Question 6

Outputs of slow carbon cycle

Answer 6

• chemical weathering processes are the result of precipitation charged with CO2 from the atmosphere which forms a weak acid. This acid attacks carbonate minerals in rocks releasing CO2 to atmosphere and dissolved form to streams, rivers, oceans
• on land, decomposed organic material may be buried underneath younger sediments to form carbonaceous rocks

Question 7

Inputs of fast carbon cycle

Answer 7

• carbon circulates between atmosphere, oceans, living organisms and soils. These are 10-1000 times faster than those in slow carbon cycle
• phytoplankton key components- through photosynethesis they absorb CO2 from atmosphere and combine it with water to make carbohydrates

Question 8

Outputs of fast carbon cycle

Answer 8

• respiration and photosynthesis return CO2 to atmosphere
• carbon exchange occurs between atmosphere and oceans. Atmospheric CO2 dissolves in ocean surface waters while oceans ventilate CO2 back to atmosphere. Through this exchange individual carbon atoms are stored for 350 years