Polar Regions Flashcards
Arctic Geography
Ice covered ocean and surrounding land
Boundaries:
- Tree line, Mean July 10 Degree isotherm, Arctic circle
14.5 million km2 ocean basin, same size as Antarctic continent
Arctic geological history
Divided into 2 basins:
- Eurasian basin
- Amerasian basin
Eurasian basin formed during the Cenozoic era (began 65 Mya)
Amerasian basin formed earlier during Mesozoic (250-65 mya)
Opening of Fram Strait, 17.5 Mya, opened North Atlantic to the Arctic
Antarctica
Ice-covered continent, geographically isolated.
14 million km2
Mountainous, transantarctic mountain chain
break up of Gondwana 180 Mya
Oceanographic isolation 40 Mya
Differences in physical features
Continental shelf:
- Arctic, 200m
- Antarctic: 500m
Temperature
Both v cold
Annual mean temp in S pole winter is -60 and N pole is -40.
Antarctic is colder due to elevation and being drier
As it is a continent parts of it are very far from ocean so doesn’t have a climate moderating effect
Ice
Glacier ice and sea ice
Arctic is semi-enclosed so sea ice is trapped in ice basins and can build up
Antarctic ice reaches out until it melts, longevity and thickness of ice is less in Antarctica
2m thickness in arctic and 1m in ant
Antarctic retreats and extends further
Arctic ocean circulation
Unique
Bering strait
Chukchi sea
Beaufort gyre
Transpolar current
Various exit gateways
north Atlantic current
Southern Ocean Circulation
Antarctic Circumpolar Current, clockwise
Largest wind driven current
Coincident with Antarctic convergence
Barrier separating Southern Ocean from Northern Ocean
Extend to 4000m depth, cold (-1 to +5 deg) and fast ( 2 knots)
Deep water formation at continental shelf of Ross and Weddell seas
Plants and animals
Plants:
- Antarctic, no tundra or tree lines. Only two flowering plant species.
- Arctic, tundra well developed and marked by a tree shrubline
mammals:
- Antarctic: no terrestrial
- Arctic: many terrestrial mammals
Antarctic and arctic, several marine mammals
Arctic Ocean Food Web
Unique complex ecosystem
- Phyto and ice algae
- Micro-zoo
- Meso-zoo
- Larger zoo
- Detritus
- Seals, walrus and polar bears
Southern Ocean food web
Very productive
Krill is keystone
Phytoplankton at base of food web
Human Presence
Antarctic governed by Antarctic Treaty System.
Arctic states
No residents at Antarctic
4 million in Arctic
First crossing of Antarctic circle in 1773
Arctic first crossing was prehistoric
Climate warming
Both poles warming
Fossil fuels less of an impact on Southern Ocean
Reducing sea ice and glacier stores
Antarctic seafloor community
Relict fauna, deep ocean derived and migrants, 8200 benthic species
High species richness:
- Pycnogonids, echinoderms, polychaetes, gastropods, amphipods.
Low species richness:
- Bivalves, crawling decapods, many fishes
Antarctic sea floor
Origins:
- cooling, 40 Mya drop of 9 to 4 deg
-Isolation, opening of drake passage, establishment of ACC.
- Long history of evolution in situ
Unique:
- Strict physiological limits, stenothermal (-1.85 to +2)
- Slow physiological rates
- Growth, embryonic development, metabolism, benthic activity levels and longevity.
- Metabolic rates in Antarctic are very low, slow, except sustained swimming in fish, temperature compensated so have more mitochondria
Under represented groups in Antarctic
Teleost fishes, muscle output 1/10 at 0 than 225
Crawling decapods, inefficient Mg regulation at low temps.
Sharks, active lifestyle, expensive
No predators which consume hard organisms
Coincident with global cooling trend, late Eocene 40 Mya
These groups couldn’t survive
Why is Antarctic interesting and important
Decadal means of summer surface temp anomalies for the 2nd half of 20th century
Glaciers, predominantly decreasing at accelerating rates
Precipitation increased over last century
Sea ice is retreating and length of sea-ice season shortening
Why study Antarctic benthos
Comprise vast majority of of biodiversity known in this area, ~80%
Extremely vulnerable to warming.
- Strict physiological limits.
- Slow physiological rates and impaired fundamental biological functions
- Limited intrinsic physiological flexibility to cope with change.
Effect of increasing temp
IPCC predicts global sea water temp may rise 2-4 deg in next 100 years.
Acclimation to a new temp, ability to cope.
Inability to perform fundamental biological functions at critical temperature.
Will ice melt be significant
Melting conditions accelerating on the Antarctic Peninsula.
- Retreating glaciers.
- Increased flow rate.
- Ice sheet collapse
- Changes in productivity
More icebergs
Scour the seafloor:
- Promote biodiversity over large areas
- Catastrophic effects on local biodiversity if persistent.
Alien species
Lithodid crabs excluded from cold Antarctic continental shelf waters for 40 mya.
Large populations of predatory king crabs in the deep water of W Antarctic Peninsula
14 species now known in Southern Ocean
Slow growth and developent
Longevity
SST has risen by a degree in last 50 years, shelf waters show increase of 0.01 deg per year.
