Polar Regions Flashcards
What are the consequences of climate change in polar regions?
+Collapse of ice shelves.
+Less sea ice.
+Increased melt conditions
What are the geological features of the Arctic?
+Ice covered ocean + surrounding land.
+14.5 sq million km.
What is the boundary of the Arctic defined by?
The treeline, 10 deg.C July Isotherm, or the Arctic circle (66 deg, 33’ 44”)
What are the names of the two basins that form the Arctic?
The Eurasian basin and the Amerasian basin.
When was the Eurasian basin formed?
During the cenozoic era (~56Mya)
When was the Amerasian basin formed?
During the Mesozoic (250-65Mya).
What are the geological features of Antarctica?
+Ice covered continent, geographically isolated.
+14 million sq km.
+Mountainous: transantarctic chain
+Land to east higher than land to west.
When did Antarctica form?
+Breakup of Gondwana: 180 Mya
+Oceanographic isolation: 40 Mya
What are the depths of the Antarctic and Arctic continental shelves?
Arctic: 100-200m
Antarctic: 400-500m.
What is the average summer and winter temperatures for the Arctic?
Winter temperatures can drop -50 deg.C and summer temperatures from -10 to 10 deg.C.
What are the average winter and summer temperatures of the Antarctic.
Winter: -49 deg.C. Summer: -20 deg.C
What are the two main types of ice?
+Glacier ice (glaciers + icebergs)
+Sea ice (pack ice +multiyear ice)
What is glacier ice formed from?
Compacted snow/frozen fresh water.
What is sea ice formed from?
Freezing of seawater. Frazil ice –> grease ice –> sea ice.
What is multiyear ice?
Persists over melt seasons - more common in arctic.
Why are there such drastic differences in sea ice in the two poles?
Different geography - landmass surrounded by ocean + semi-enclosed ocean.
Why is there more sea ice in the arctic?
+Lots of freshwater input.
+Reduced ice flow.
+Build up o thick ridges: 3-8m - greater longevity.
+7 million sq km multiyear.
Why is there less sea ice in the antarctic?
Lots of drift to warmer water - more annual ice. Longevity and thickness less in antarctica.
What is the difference in geographic distribution?
Arctic: asymmetric - due to ocean currents.
Antarctic: symmetric - due to circumpolar flow.
What is the difference in snow thickness?
Arctic: thinner.
Antarctic: thicker due to surrounded ocean - more precipitation.
What is the circulation of the arctic like?
Unique: ice covered + relatively isolated. Contains bering strait, chukchi sea, beaufort gyre, transpolar current & north atlantic current.
What is the circulation of the antarctic ocean like?
+Antarctic circumpolar current (ACC) W-E c/w.
- Largest wind driven current.
- Coincident with Antarctic Convergence Barrier seperating SO from north oceans.
- Extends to 4000m, -1 - 5 deg.C, fast (2 knots)
What are the plants of the Antarctic and Arctic like?
Antarctic: NO tundra/tree lines.
Arctic: Tundra well developed + marked by tree shrubline.
What are the mammals of the arctic/antarctic like?
Antarctic: No terrestrial mammals.
Arctic: Many terrestrial mammals.
Both: Several marine mammals, w/ exception of polar bears in Antarctica.
What is the food web of the arctic like?
+Unique, complex ecosystem.
+Sea-ice biota.
+Ice algae and phytoplankton.
+Climate change - cascading effects.
What is the food web of the antarctic like? (4pt)
+Can be relatively simple.
+Very productive - phytoplankton underpin food web.
+Krill are key.
+Ice is important component.
What are the human impacts of antarctica?
+No government/belongs to no country.
+No permanent residents, sparse scientific population.
+First crossing of A. circle James Cook, jan 17, 1773.
What are the human interactions in the Arctic?
+Nations include russia, canada, greenland, USA, iceland, norway, sweden, finland.
+Population 60 deg. North >4 million.
+First crossing prehistoric.
Why are polar regions important? (4pt)
+Cornerstones of global ecosystem.
+Barometers of planet health.
+Messengers of global processes.
+Regulators & drivers of world climate.
What are the effects of climate change in the Arctic?
Rapid rise in air temp (x2 global average), reduction in sea ice + faster flowing glaciers.
What are the effects of climate change in the Antarctic?
Increase in sea ice, receding glaciers + change in ocean productivity.
What drives both polar food webs?
Ice biota and krill.
What are the characteristics of the Southern ocean?
All water south of polar front, with Clockwise surface currents from W-E (ACC). Unique:
+Low stable temperatures.
+Seasonal signal in production.
+Deep continental shelf (Weight of ice cap + erosion).
What are the organisms with high species richness in the southern ocean? (7pt)
\+Pycnogonids \+Sponges \+Echinoderms \+Tunicates \+Polychaetes \+Gastropods \+Amphipods and isopods.
What are organisms in the southern ocean with low species richness?
+Bivalves
+Reptant (crawling) decapods.
+Many fishes e.g. Teleosts
What are the origins of the southern ocean benthic community?
+Cooling (40 Mya, 4 - 9 deg.C)
+Isolation - opening Drake’s passage (Polar front, ACC)
+Long history of evoltion in situ, elevated endemism.
Why is the southern ocean benthic community unique?
+Strict physiological limits - stenothermal (-1.85 - +2 deg.C)
+Slow physological rates - growth, embryonic development, metabolism, benthic activity levels and longevity.
+Underrepresented e.g. durophagous predators in Antarctica.
Why are there no durophagous predators in Antarctica?
+Teleostean fish: muscle power at 0 deg.C 1/10th than at 25 deg.C
+Reptant decapods: inefficient ion regulation at low temps, narcotic effect.
+Sharks: active lifestyle prohibitively expensive.
Why study Antarctic benthos?
+Comprise vat majority of biodiversity known around Antarctica (~80%)
+Antarctic benthos extremely vulnerable to climate warming.
Why are Antarctic benthos so vulnerable to global warming?
+Strict physiological limits, i.e. Stenothermy.
+Slow physiological rates + impaired fundamental biological functions.
+Limited intrinsic physiological flexibility to cope with change.
What will accelerated melt conditions on the antarctic peninsula cause?
+Retreating glaciers.
+Increased flow rate
+Ice sheet collapse.
What will the effects of more ice bergs be?
Scour the seafloor:
+Promote biodiversity over large areas
+Catastrophic effects on local biodiversity.
What is the relationship between the surface ocean and seafloor?
Seafloor organisms are reliant upon export flux of carbon from surface ocean for food (pelagic-benthic coupling)
Seafloor organisms are vital for healthy marine ecosystems.
What drives ecological processes under a climate change scenario from October to November (late spring)?
+Sea ice cover breaking up - nearing 24hr daylight.
+Ice-algae released by melting ice and melt-water induced stratification of water column begins.
What drives ecological processes under a climate change scenario from January to March (Austral summer)?
Sea ice over receded and phytoplankton bloom fully developed, sedimentation of organic material can produce thick phytodetrital carpet.
What drives ecological processes under a climate change scenario from May to July (late autumn)?
Nearly 24hr darkness, sea ice forms, low phytoplankton biomass.
What drives ecological processes under a climate change scenario from August to September (late winter)?
Period of maximum sea ice coverage, short but lengthening daylight hours.
Relatively harsh winter.
Expect to see strong seasonality in food availability at seafloor.
What is the FOODBANCS hypothesis?
Sea ice retreat and intense summer phytoplankton blooms yield substantial summer deposition of algal detritus onto the WAP shelf floor, deposited bloom material then provides a sustained source of food (“food bank”) for seafloor animals during winter months.
Will environmental change introduce alien species?
yes. Lithodid (king) crabs have been excluded from cold antarctic continental shelf waters for Mya, but now large populations discovered in deep water off west antarctic peninsula.
Slow growth and development - longevity.
