Water + Carbon cycles: diurnal, seasonal + long term changes

Question 1

explain the diurnal (short term) changes to the water cycle

Answer 1

• lower temperatures at night reduce evaporation + transpiration
• higher temperatures during the day increase evaporation + transpiration
• convectional precipitation, dependent on direct heating of the ground by the Sun, is a daytime phenomenon - often falling in the afternoon when temperatures are highest

Question 2

explain the seasonal (short term) changes to the water cycle

Answer 2

• seasons are controlled by variations in solar radiation
• (UK) solar radiation intensity peaks in mid-June = evapotranspiration is highest in summer + lowest in winter
• in driest parts of England, up to 80% of precipitation may be lost to evapotranspiration

Question 3

explain the long term changes to the water cycle

Answer 3

• during glacial periods, the wc undergoes changes:
• the net transfer of water form oceans to storage in ice sheets, glaciers + permafrost. as a result, sea level falls by 100-130m
• ice sheets advance towards equator, destroying forests + grassland = water stored in biosphere shrinks
• lower rates of evapotranspiration during glacial periods reduce exchanges of water between the atmosphere, ocean, biosphere + soil
• reduction in evapotranspiration + storage of water in ice sheets/glaciers/permafrost slows water cycle significantly

Question 4

explain the seasonal changes to the carbon cycle

Answer 4

• seasonal changes are shown by month-to-month changes in NPP of vegetation
• photo period (day length (sunlight)) + temperature mainly drive changes in NPP
• during summer, net global flows of CO2 from the atmos. to the biosphere causing atmospheric CO2 levels to fall by abt 0.5%
• during growing season, ecosystems extract huge amounts of CO2 from the atmosphere
• phytoplankton (in oceans) are stimulated by rising water temperatures, more intense sunlight + longer photoperiod - yearly explosion of marine plan life, which starts in March + peaks in mid-summer

Question 5

explain the long term changes to the carbon cycle

Answer 5

• during glacial periods there was a dramatic reduction of CO2 in atmosphere
• carbon pool in vegetation shrinks as ice sheets advance + occupy large areas
• w much of surface being covered by ice, carbon stored in soils no longer be exchanged in atmosphere
• permafrost sequester carbon becoming carbon sinks
• NPP + total volume of carbon photosynthesis falls
• implications are overall slowing of carbon flux + smaller amounts of CO2 are returned to atmos. through decomposition