Arctic Tundra Flashcards
(20 cards)
Water cycle - 2 main parts
- Physical factors
- Seasonal changes
Arctic tundra size
- 8 million km squared
- major biome
AT - 3 countries
- Alaska
- N Canada
- Siberia
Temperatures
- Incredibly low
-15 degrees C average- 40 coldest in deepest winter
- Negative heat balance for 8/9 months per year
- below freezing
- more heat lost to atmosphere than gained to surface from solar radiation
- seasonal change (change over time) impacts water cycle
Rainfall
- little precipitation of any form
- 50 to 350 mm average per year (very low)
- less than 100 mm most areas
- 10% of Amazon - most precipitation falls as snow
- low temperatures mean much of moisture not stored in atmosphere
- below absolute humidity
- air can’t hold much moisture
- Amazon warmth enables lots of moisture held in atmosphere - limited transpiration from surface - lack of plant growth
Permafrost - definition and barrier to infiltration
- Layer permanently frozen throughout year - the layer above it changes
- soil and ice just below surface
- stay as rigid barrier for most of year
- barrier to infiltration of water
- prevent deeper percolation
- limited aquifer storage
- soil moisture very limited
Variation in vegetation
- Summer, short growing season
- just above freezing
- more daylight hours
- Plants adapted to this
- Very low to ground
- Small leaves - low transpiration
- Won’t need much precipitation to grow
- Spacial differences between north / south
High arctic variation in vegetation (far north)
- far north more extreme environment
- less vegetation
- more bare ground
Temperature change over time
- Long term potential change
- Greenhouse effect climate change
- Higher temperatures
- Potential for more areas of the Arctic to become more green
- e.g. Northern Quebec see increased vegetation with rising temperatures
- Cause unknown changes to water and carbon cycles
Water flows
- Slow
- limited precipitation and transpiration
- lot stored on surface - permafrost
Seasonal change
- Change within a year - seasonal
- Top soil layer = active layer
- Slight thawing spring / summer
- Higher water content in soil, limited to top layer
- Winter most water stored as permafrost or snow on surface
- winter = limited vegetation so limited evapotranspiration
- Summer liquid water on surface
- active layer melted, sits on surface above permafrost
- thousands of temporary ponds and lakes
- small amount evapotranspiration in short growing season
AT geology
- Much of tundra made of precambrian igneous rock
- e.g. Canadian shield, huge area precambrian igneous rock, millions of km
- similar rock types in Siberia and other parts Arctic Tundra - fairly uniform geology- very impermeable = standing water
- permafrost and rock make double layer prevent water penetrate down to aquifers
- Much of tundra uniform relief
- Very flat. Some gentle slopes.
- Relief aids little infiltration = waterlog
- winter, snow stays
- summer, water stays without draining.
- Steep slopes would run-off and form rivers.
- Some areas lower arctic more like forest with slopes.
- Rivers will form.
Carbon cycle
Slow - not many transfers between stores
* Not getting carbon dioxide from atmosphere transferred to biosphere
* Limited photosynthesis and plant growth - poor conditions:
- Not much liquid water
- Low temperatures
- Not much rainfall
- Large crystaline igneous rock
- Doesn’t break down so provides few nutrients
Flows and stores - primary productivity
- Very short summer period (about 3 months)
- lots of plant growth (sunlight hours, above negative heat balance)
- Averaged over whole year:
- Net primary productivity - very low, 200g per m squared per year - low for any biome
- poor conditions photosynthesis, shor window for growth
Flows and stores - seasonal changes
Seasonal changes in the stores
- overall limited biomass in biostore
- biomass carbon store 4 to 29 tonnes per hectare (Amazon much more)
Summer - plants drop leaf litter, decompose and go into soil
- some carbon from limited vegetation transferred to soil
- microorganisms in active layer e.g. bacteria and other decomposers more active in warmth
- break down some of leaf layer and release CO2 via respiration to atmosphere
- some movement of carbon as seasons change
Flows and stores - impacts of waterlogging
When active layer defrosts, lots of flooding and seasonal pools
- waterlogged conditions
- decomposers need oxygen to break down organic matter, especially below surface
- decomposition and therefore respiration very limited with increased water
Limits amounts of CO2 goes to atmospere
Permafrost - carbon storage
Permafrost = one of most imporant carbon stores
- carbon sink
- stores over 1600 giga tonnes
So much carbon stored as:
- full of organic matter (dead animals and plants) frozen in soil thousands of years or more
- doesn’t melt - 9 months of year very low temperatures prevent break down of matter
- carbon trapped for thousands of years, remains and not released
Permafrost - future change
Permafrost is carbon sink
- In the future could become carbon source
- Temperature increase from global greenhouse gasses
- Permanently frozen layer will start to thaw
- Allow decomposers / microorganisms to attack organic matter within
- Start to decay / decompose, release CO2 for respiration
- Pockets of methane trapped in permafrost, released with warming into atmosphere
- More CO2 and methane released into atmosphere = increase in greenhouse gasses
- positive feedback loop, cause lots of problems for global temperatures
- Permanent removal of permafrost (8 million km+)
- significant amout of carbon released to atmosphere
Future for AT
- Climate change worsen
- Permafrost melts - release CO2 and methane
- Methane 4 x more damaging than CO2
- Alternatively…
- Permafrost melt, more liquid water
- More water combined with higher temperatures = increased photosynthesis
- Increased plant growth extract carbon from atmosphere
- Stored in biosphere
- Best predictions suggest increased plant growth caused by CO2 not sufficient
- only offset methane released by 20%
- arctic eventually become carbon source
- Predictions from modelling - can’t be measured currently
Summary - carbon cycle
- Generally carbon cycle very slow in arctic
- seasonal change flows and stores
- largely because of severe physical conditions
- low temperatures, little water, little nutriets from geology
- largely because of severe physical conditions
- lots of carbon stored in permafrost
- might see future change with climate change
