3.B - short term and long term changes to water/carbon cycle Flashcards
how do carbon cycle flows and stores change naturally?
- interglacial/glacial periods
- summer
- volcanic eruptions
- winter
- natural disasters
how do interglacial/glacial periods change the carbon cycle naturally?
- methane trapped in glacial ice/permafrost can be released when melted
- during glacial rates of photosynthesis are reduced
how do natural disasters change the carbon cycle naturally?
- e.g. tsunami
- destruction of terrestrial vegetation
- destroy coral reefs - massive carbon stores
- could cause rapid cycling of carbon stored in the oceans
how does the summer change the carbon cycle naturally?
- ↑ combustion due to forest fires. terrestrial carbon released as atmospheric carbon
- permafrost active layer melts = ↑ rates of decomposition and therefore CO2 in the atmosphere
- more photosynthesis due to ↑ temp/insolation
(more of an influence in the N hemisphere due to more land and trees)
how do volcanic eruptions change the carbon cycle naturally?
- releases loads of climate changing CO2 and CH4
how does the winter change the carbon cycle naturally?
less photosynthesis in woodlands due to less leaves
how do water cycle flows and stores change naturally?
- forest fires
- seasonal rates
- glacial/interglacial
- sea level rise
how do forest fires change the water cycle naturally?
- trees burn down = ↓ rates of interception, less evapotranspiration = less precipitation
how does seasonal change alter the water cycle naturally?
- seasonal evapotranspiration rates - warmer in summer so flows are faster
- opposite in winter
- therefore river discharge levels in winter are higher because there are less outputs through plants/evaporation so more water reaches the river
how do interglacial/glacial periods change the water cycle naturally?
- LONG TERM
- 12,000 years ago, huge ice sheets were covering Europe/N America
- change stores of water (glaciers/ice caps grow)
- change volume of permafrost. if water is frozen then flows stop occuring.
how does sea level rise change the water cycle naturally?
LONG TERM
- sea level was 120m lower
- flandrian transgression
how does summer change the water cycle naturally?
- SHORT TERM
- ice/glacial melts in summer ↑ river discharge
what are short term changes?
- short term changes are those that occur daily (diurnally) or seasonally
- there are short term changes in climate, temperature, sunlight and foliage that bring about changes in the carbon and water cycles
how does convectional rainfall cause diurnal change in the water cycle? (amazon)
- as temperature falls overnight, evapotranspiration reduces the flow of water to the atmosphere
- however, this will increase as daytime temperatures begin to rise
- temperature is going to drive evaporation and sunlight will drive photosynthesis (thus transpiration)
- this means typically in the amazon we get convectional rainfall occuring at 4pm
how will the pattern of incoming radiation create a diurnal pattern of flows of water?
- lower temps at night reduce evaporation and transpiration
- convectional precipitation, dependent on direct heating of the ground surface by the sun, is a daytime phenomenon, often falling in the afternoon when temps reach a maximum
- this is particularly significant in climatic regions in the tropics, where the bulk of precipitation is from convectional storms
why will there be a diurnal pattern of CO2?
- during the daytime CO2 flows from the atmosphere to vegetation
- at night the flux is reversed
- w/o sunlight, photosynthesis is stopped and vegetation loses CO2 to the atmosphere
- this is more pronounced in places with lots of vegetation because of the ↑ rates photosynthesis and respiration
what controls the season and where will these changes be more pronounced?
- ultimately the seasons are controlled by variations in the intensity of solar radiation
- as you move further away from the equator, seasonal changes become more severe
- largest seasonal changes = arctic and antarctic
how and why does atmospheric CO2 change in the northern hemisphere summer?
- when trees are in full foliage, there is a net global flow of CO2 from the atmosphere to the biosphere
- this causes atmospheric CO2 levels to decrease
- at the end of summer, as photosynthesis ends, the flow is reversed w natural decomposition releasing CO2 back to the atmosphere
- seasonal fluctuation in the global CO2 flux are explained by the conc of land masses in the N hemisphere
how does the ocean change seasonally?
- in the oceans phytoplankton are stimulated into photosynthetic activity by rising water temps, more intense sunlight and the lengthening photoperiod
- every year in the N Atlantic there is an explosion of microscopic oceanic plant life which starts in March and peaks in mid summer
- the resulting algal blooms are so extensive they are visible from space
describe the trends in ocean chlorophyll and suggest why this is occuring
- ocean chlorophyll is concentrated above the tropic of cancer in high levels and is at lower levels closer to the equator
- colder oceans = carbon sink = carbon isnt a limiting factor in ocean photosynthesis
how do trends of ocean chlorophyll affect the carbon cycle?
- indicates the amount of phytoplankton present in the ocean and therefore how much carbon is taken out of the atmosphere in photosynthesis
- transfers carbon from atmospheric store to ocean sequestration
why is the growing season of Barrow so limited?
- limited to 50-60 days of the year
- lack of liquid water for most of the year due to temps below freezing
- no decompostition for most of the year
- stored in permafrost
- photosynthesis 24hrs/day in growing season
how will seasonal changes in alaska differ to seasonal changes in the tropical rainforest?
- rainforest doesn’t really have seasons
- 28C all year round
- lots of decompostition v. quickly but lots of photosynthesis due to abundance of trees
how will flows in the water cycle change seasonally in southern England?
e.g. Oxfordshire
- transpiration is more prominent in summer = soil gets drier
- temperatures and solar input are highest in the summer months
- rates of evapotranspiration are high in the summer and so there is an ↑ in the flow from groundwater and soil stores to the atmosphere
- this means generally river discharge is lower in the UK summer months even though rainfall does not drop significantly
how will flows in the water cycle change seasonally in Mckenzie River, Canada?
- Mckenzie River
- much higher river discharge in summer
- frozen in winter months and water stored in glaciers/permafrost
- melts in summer = ↑ discharge
what are long term changes?
- long term changes are those that occur over thousands or millions of years
- such changes are particularly evident during the last 2.5 mill years (a period known as the Quaternary)
- this is a time period characterised by the advance and retreat of continental ice sheets
- as the climate and global temperatures have fluctuated, so has the water cycle
what is the Quaternary period
the last 2.5 mill years
how has the carbon cycle changed over the past 400,000 years?
- CO2 conc has fluctuated
- carbon is locked up in permafrost.
- as temps have gone down, so has CO2 in glacial periods
- when its colder, everything is much slower
- less photosynthesis and NO decomposition = less CO2 in atmosphere
- CO2 is more soluble in cold oceans
- warming = return flow to the atmosphere
- CO2 and temp are linked
during a glacial period, how will the water cycle be affected?
- transfer of water from the ocean reservoir to storage in ice sheets, glaciers and permafrost
- as a result, in glacials the sea level world-wide falls by 100-130m; and ice sheets and glacier expand to cover around 1/3 of the continental land mass
- as ice sheets advance equator-wards they destroy extensive tracts of forest and grasslands
- the biosphere store of water shrinks
- in tropics, climate becomes drier and deserts/grassland displace large areas of rainforest
- lower rates of evapotranspiration during glacial phases ↓ exchange of water between the atmosphere and the oceans, biosphere and soils. slows the water cycle
how could a cooler climate affect the carbon cycle in the tropical regions?
- grasslands encroach on tropical rainforests as ice sheets advance and occupy large areas of continents
- therefore the carbon pool in vegetation shrinks during glacials
- w/ less vegetation cover, fewer forests, lower temps and lower precipitation, NPP and the total volume of carbon fixed in photosynthesis will be ↓
= slowing of the carbon flux and smaller amounts of CO2 returned to atmosphere through decomposition
how might evapotranspiration rates be affected by cooler climates?
- lower rates of evapotranspiration during glacial phases ↓ exchanges of water between the atmosphere and the oceans, biosphere and soils
- slows the water cycle
how could CO2 levels be caused to fall naturally?
GLACIAL PERIODS
- with much of the land surface buried by ice, carbon stored in soils will no longer be exchanged with the atmosphere
- meanwhile, expanses of tundra beyond the ice limit sequester huge amounts of carbon in permafrost
why does the terrestrial carbon sink decrease during glacial periods?
with:
- less vegetation cover,
- fewer forests,
- lower temperatures
- and lower precipitation,
NPP will decline
how else can a glacial period affect stores and flows of carbon in different regions?
- the implications are an overall slowing of the carbon flux and smaller amounts of CO2 returned to the atmosphere through decomposition
- it is possible that excess CO2 finds its way from the atmosphere to the deep ocean
- lower ocean temps also make CO2 more soluble in surface waters
- changes in ocean circulation during glacials that bring nutrients to the surface and stimulate phytoplankton growth.
what are the impacts of glaciation on the water cycle?
- sea levels fall (120m lower than today in last glacial period)
- ice sheets such as the Cordileran (NA) or Scandinavian start to advance
- the store of water in ice (cryosphere) starts to increase
- because vegetation is covered by advancing ice the biosphere store is reduced. in periglacial areas on the edge of an ice sheet tundra replaces forest. soil stores of water ↑ due to permafrost
- water cycle generally slows down as evapotranspiration is decreased
what are the impacts of glaciation on the carbon cycle?
- more carbon is stored in the oceans as phytoplankton bloom due to changes in ocean circulation
- carbon dioxide is also more soluble in cold water and ocean temperatures will drop therefore more carbon is taken up by oceans, reducing carbon dioxide in the atmosphere
- because of the increase in ice coverage there is less vegetation and colder climates have reduced NPP
- this will mean a ↓ in carbon stored in plants
- permafrost/ice cover as well as colder temps mean there is less decomposition and therefore a reduction in the flow between the soil and atmosphere
why do we monitor the carbon or water cycles?
- calculate NPP of areas (if its a sink/store)
- how disasters/ significant events affect carbon and water cycles
- assess/measure flood risk
- impacts of human activity on the cycles
- limits of resources - how far a system can be altered before causing damage
- do certain areas need policing?
how can we monitor the carbon or water cycles?
- carbon and water content on a local scale
- infiltration/interception rates
- plant teabags to measure decomp
- carbon content of trees and type of trees to estimate above ground biomass
- satelliete coverage of trees
- measure factory carbon emissions
how can deforestation data be helpful?
- this sort of data can be used to give an insight around the rates of deforestation and could change behaviour patterns in terms of pollution
- can be used to predict and therefore mitigate against deforestation
- local govs can therefore concentrate resources into areas where deforestation is a growing issue
- difficult to gather
- small scale imaging doesn’t show full picture
how can sea ice data be useful?
- the data gathered by NASA could be used to predict future changes regarding the Arctic sea ice conc
- would help to aid projections of future climate change which is heightened as a result of the arctic amplification feedback loop
- “pole hole” - north of this satellite sensors have historically been unable to collect data.
how could global mean sea level data be helpful?
- can help small scale coastal towns predict if they are safe (esp low lying places)
- estimates how much the sea level will rise in the next 100 yrs if the rate remains the same
- hasnt been recorded for 30 yrs
- doesnt consider natural climate change
- only 1 rate of sea level rise - it might be different in different locations
how could snow/ice extent data be useful?
- useful for showing seasonal and monthly changes over a few decades
- however, because its only for the past 60 yrs, changes arent massive.
- more significant changes would be shown if the data could cover 10,000s of years due to glacial/interglacial periods
- shows an average gentle decrease in ice coverage for all regions, demonstrating effects of global warming - impacts of human actions on a global scale rather than just locally
how could snow/ice extent data be useful?
- measures the amount of water inside and size of the plant to get and idea of the vegetation overally
- look for areas of increased drought risk
- identify areas with an enhanced risk of malaria
- could infer NPP/flood risk of different areas
- shows seasonal change
- show human actions of deforestation
- see on a much larger scale than being physically there
- unable to change scale and therefore can only see the global patterns and not local change
