3. Short/long term changes to water and carbon cycle Flashcards
How can short term changes be categorised?
Diurnal and seasonal changes
Describe diurnal changes on the water cycle:
Significant changes can occur within 24 hours
- Evaporation and transpiration are much lower at night as temperatures drop
- Downpours in the afternoon as a result of intense convectional heating
Describe diurnal changes on the carbon cycle:
At night there are low levels of sunlight so photosynthesis is severely reduced for vegetation and phytoplankton so less CO2 absorbed at night
Vice versa for the day
Describe seasonal changes on the water cycle:
Different seasons have varying inputs of solar radiation which influences rates of evapotranspiration (highest in summer) and precipitation (
EG solar input in June in UK is 800W/m2 compared to December at 150 W/m2
Describe seasonal changes on the carbon cycle:
Variations in NPP
EG During summer in northern hemisphere there is a net flow of CO2 from the atmosphere to the biosphere as photosynthesis is rapid
Long term changes: what is a glacial?
A prolonged cold climatic phase lasting for tens of thousands of years that causes continental glaciation
Describe the impact of glacials on the water cycle:
- Sea levels decrease by 100-130 metres
- Ice sheets and glaciers expand which destroys forests (water stored in the biosphere shrinks)
- Evapotranspiration declines
- Water cycle slows
In the past. 400,000 years, how many major glacial cycles have there been?
4
Describe the impact of glacials on the carbon cycle:
- Less CO2 in the atmosphere
- Changes in oceanic circulation bring nutrients to surface where phytoplankton grow and photosynthesise rapidly = fixes CO2 and when they die this is stored in the deep ocean
- Less exchange of carbon between soil and atmosphere due to ice coverage
- Ice coverage means less vegetation so less carbon fixation by photosynthesis
