Polar ecosystems Arctic/Antarctic contrasts Tundra - the physical template
(climate, landforms, soils) Tundra plant and animal communities Winter survival Population cycles Management issues Responses to future climate change
Arctic(a) vs. Antarctica
land: 8 X 106 km2 (30% ice)
substantial terrestrial food
land mammals
herbivorous & insectivorous birds
land: 14 X 106 km2 (97% ice)
no terrestrial food
no land mammals
no herbivorous or insectivorous birds
Arctic(a) vs. Antarctica not
geographically isolated
glacial refuges ice-free coastal
zone in summer relatively high
plant and animal diversity
geographically isolated
no? glacial refuges
v. restricted ice-free coastal zone in summer
low plant and animal diversity
Tundra ecosystems
“tundra” = treeless barrens
Global distribution of tundra
Arctic ecosystems in Canada
N.Arctic = polar desert
S.Arctic = tundra
Tundra ecosystems
Tundra ecosystems are associated with areas of extreme near-polar climate which operates either directly, or through a series of environmental forcings (primarily thaw-layer dynamics) to limit productivity and biodiversity.
Tundra ecosystems
Low species diversity may promote instability. This is expressed by highly cyclic behaviour.
Arctic communities are geologically-recent developments in the planetary biome landscape.
Day-length and insolationat top of atmosphere
Equator
40°N
60°N
90°N
Inso
lati
on
(w m
-2)
0
100
200
300
400
500
600
daylength (North Pole) 0h 12h 24h 12h 0h
J M J S D
Tundra climate stations
Barrow
Churchill
IqaluitSvalbard
Tiksi
Gulf Stream
Treeline
60°N
75°N
Mean monthly temperatures,tundra climate stations
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
J F M A M J J A S O N D
Barrow,AK
Churchill
Iqaluit
Svalbard
Tiksi
Mean monthly precipitationtundra climate stations
J F M A M J J A S O ND
Barrow,AK
Tiksi
ChurchillIqaluit
Svalbard0
10
20
30
40
50
60
70
Barrow,AK
Tiksi
Churchill
Iqaluit
Svalbard
Synoptic climatology(after Reid Bryson)
Treeline
Mean position of Polar Front (July)
ARCTIC airmass
Bering Sea ice
Frost-free days
Treeline
Mean annual snowfall (mm)
Treeline
Permafrost distribution(note transect lines
and presence of sub-sea
permafrost)
Alaska
Siberia
Boreal forest Tundra
Permafrost
patchy discontinuous continuous
120 30 mean #d >10°C
mean locationPolar FrontJulyJan
150 240 mean #d <0°C
treegrowth
pollen/seedviability
150 60 frost-free days
The critical thaw period
Data from Barrow, AK
~70 d
~40 d
Microclimatology: slope and aspect
Aspect Flat South-facing North-facingSlope (°)Ground-Sunangle (°)0 10 20 40 10 20 4045 55 65 85 35 25 5210Direct-beam radiation, solar noon, summer solstice, 68.5°N
forest?
Vigorous tree growth on south-facing slopes near
treeline
Polar montane environments:
freeze-thaw weathering -
felsenmeer and talus cones
Polar uplands:
thaw-layer dynamics
and solifluction
Polar lowlands
Cryoturbation and patterned ground
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
dwarf shrubs,grasses
sedges,lichens
Frost polygons: note unvegetated ‘boils’ and standing water in cracks
Tundra floras(product of late Tertiary cooling and landbridges during glacial phases?
Centre-of-origin?
Davis Strait “gap”(major floristic contrast)
Plio-Pleistocene
migration
Plio-Pleistocene
migration
Alpine highlandsof NE Asia
Topography Tundratype
Flora Thawdepth(m)
Organiclayer (m)
rocky, well-drainedridges
Heath evergreenshrubs
>2 <0.1
gentlyrolling
Tussock Eriophorum 0.3-0.5 <0.3
flatlowlands
Wetsedge
graminoids 0.2-0.3 0.1-0.5
well-drainedalluvialsites
Shrub deciduousshrubs
>1 thin?
Tundra vegetation-soil catenas
Sedge Shrub Sedge Tussock Heath
0 organics
sandysoil
permafrost
rockysoil
silty soilsilty soil
Depth (m)
1
2
Felsen-meer
Felsenmeer vegetation dominated by lichens
Evergreen heath tundra
Dominated by Ericaceae (heaths), such as Cassiope
Heath tundra is floristically more diverse than other tundra types
Tussock tundra
(dominated by Eriophorum)
[cotton grass]
Wet sedge tundra:
dominated by graminoids (e.g. Carex, Dupontia)
Animal life
Surviving winterStrategy Organisms
Distant migration Local migration Above snow-pack
heavy insulation
protective colouring
Below snow-pack Hibernation Dormant phase
birds caribou
ground squirrelsplants, insects
muskox, polar bear
lemmings, voles
arctic fox, ptarmigan
Are cyclical population dynamics
(~4 yr period)a product of simple food
webs?(note difference in time
scales)
Vole data: N. FinlandLemming data: N. Norway
Lemming distribution
The tundra phosphorus cycle
lemmings/ha 2-12 2-12 40-50 180-200 jaegers uncommon uncommon breeding breeding(pairs/km2) no breeding no breeding 10 40-50snowy owls scarce scarce breeding breeding(pairs/km2) no breeding no breeding 0.1 0.2shorteared absent absent 1 record 10/km2
owls
Active layer
Permafrost
CaCa
Ca
CaN
NN
N
P
PP
P
K KK
K
Forage (%P) 0.2 0.2 0.3 0.6quality
•• ••••Litter layer thin thick
Caribou dynamics
The ANWR debate
Porcupine herd migrations: radio-collared females at calving grounds on
Arctic Alaska coastal plain
Winter feeding grounds in Yukon, Porcupine caribou herd (1998-99)
300 k
m
Snow goose dynamics
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Lesser snow goose flock
~4 M geese breed in the marshes of the
Canadian Arctic
birds
devegetatedarea
Jeffries et al., 2006. J. Ecol. 94, 234-242.
Impacts of snow goose overgrazing
drying ofsurface soil
increasedsoil salinity
reduced graminoid
growth
reducedgraminoidbiomass
Intense grubbing andgrazing by snowgeese
Effects of snow goose grazing and grubbing (James Bay)
Salicornia
Puccinellia
Potential effects of climate change
Is climate change occurring in Arctic environments? - climate records short - biotic data fragmentary
Simulation modelsField experiments
Recent (post-1950) climate change in polar regions
Arctic:• Reduction in sea ice extent and thickness• Northward treeline shifts (e.g. E. coast Hudson Bay)• Increased lake productivity (e.g. Ellesmere Island)• Range expansions (e.g. dragonflies - Inuvik - 2000)Antarctic:• Ice shelf disintegration (e.g. N. Larsen & Wordie
Shelf)• Spread of flowering plants (e.g. Antarctic hairgrass
has expanded its range 25-fold since 1964)• New lichen species colonizing recently deglaciated
areas
Climate change
Climate change in the western Canadian arctic
Data: Environment Canada
Inuvik, NWT
-40
-30
-20
-10
0
10
20
30
1950 1960 1970 1980 1990 2000 2010
Year
Temperature (°C)
Monthly Max. Temp. (°C)Mean Ann. Temp. (°C)Monthly Min. Temp. (°C)
Climate change in the western Canadian arctic
Data: Environment Canada
Inuvik, NWT
0
50
100
150
200
250
300
350
400
1950 1960 1970 1980 1990 2000 2010
Year
Precipitation (mm)
Total Precip. (mm)
Snow (mm; water equivalent)
Climate change in the eastern Canadian arctic
Iqaluit, Nunavut
-40
-30
-20
-10
0
10
20
1940 1950 1960 1970 1980 1990 2000 2010
Year
Temperature (°C)
Monthly Max Temp (°C)Mean Ann. Temp. (°C)Monthly Min Temp (°C)
Data: Environment Canada
Climate change in the eastern Canadian arctic
Data: Environment Canada
Iqaluit, Nunavut
0
100
200
300
400
500
600
700
1940 1950 1960 1970 1980 1990 2000 2010
Year
Precipitation (mm)
Total Precip. (mm)
Snow (mm; waterequivalent)
Source: www.metoffice.gov.uk/.../ images/figure5.jpg
Sea-ice extent, Arctic
and Antarctic oceans
Source: Arctic Climate Impact Assessment website
The Arctic of the future
Field experiments:
ITEX sites
Impacts of climatic warming (ITEX results [1997])
inc. seedweight and
viability
increasedgraminoidabundance
reduced evergreen shrub competitiveness
increasedplant
productivity
Increased airtemperature
reducedplant diversity