L8 - The Polar Seas Flashcards
Seasonality in polar landscapes?
Highly seasonal
Why are polar landscapes so cold?
Earths tilt and orbit, the sun’s rays have to pass through more atmosphere. Low angular height of the sun during summer. High albedo (reflectance of radiation from ice.
What is earth’s tilt and orbit?
Earth’s tilt and orbit around the sun leads to seasonal and latitudinal differences in solar radiation. Months of light (summer) or dark (winter)
How do the sun’s rays pass through the atmosphere in colder climate?
Low angle of incoming sunlight. Solar radiation spread over a large surface area at higher latitudes.
How do the sun’s rays pass through the atmosphere in warmer climate?
Sunlight strikes most directly. Solar radiation concentrated over a smaller surface area at lower latitudes
What does low angular height of sun during summer mean?
High latitude (i.e. nearer the poles). Sunlight coming at a lower angle means that less is absorbed and more is reflected. 33% reflected, 67% absorbed.
What is High Albedo?
Reflectance of radiation from ice. Bright white light reflects the majority of incoming sunlight, absorbing only a small amount of hear. The darker ocean absorbs a much larger proportion of the heat coming from the sun.
What are some characteristics of the arctic ocean?
Small and shallow: 15.8 million square km (<10% of the pacific), average depth ~1200m (pacific is ~4000m). Surrounded by land, limited link with atlantic and pacific. Wide, gentle continental shelf. River runoff contributes nutrients (and pollution)
Arctic ocean - Bathymetry?
Deepest 5,450m at Molloy deep. Longest continental shelf (>900 miles) - Siberia
Arctic ocean - what is the sea temp?
Mean water temperature : -1.8 deg C.
Arctic ocean - Sea ice?
Sea ice is not permanent, winter: 15 million m squared, summer : 7 million kilometre squared. Long-term decline - 2.9% per decade loss since 1979
What are some characteristics of the Antarctic ocean?
Larger and deeper than the arctic ocean. 20.3million square km (<13% of the pacific). Average depth ~3200m (Pacific ~4000m). Surrounds a continent, extension of atlantic, indian and pacific oceans. Steep, narrow continental shelf, no river run-off.
Antarctic ocean - Sea ice?
Extent varies each year, increased by ~1% per decade (in some areas). Winter : 20million square km. Summer : 4 million square km. Antarctic meltwater, some regions retreating more than others, freshwater ice shelves feeding into the ocean.
Antarctic ocean - currents?
The antarctic circumpolar current (ACC). The clockwise flow leads to upwelling of cold, nutrient rich water. Water mixing between antarctic and sub-antarctic waters.
What is a dominant force in polar marine ecosystems?
Sea ice it affects ecology, a unique habitat for microalgae, bacteria, protozoa. Food for krill, supports sea birds, mammals, and fish.
Where is there high seasonal productivity in polar marine ecosystems?
At the ice edge (spring and summer). Supports large krill populations
What is life in ice like?
Sea ice provides a surface area. Organisms and nutrients can adhere to it - plankton, flatworms, crustaceans, bacteria. The edge is often more nutrient rich than the surrounding water. Melting ice releases these nutrients and allows light to penetrate further into the water.
What is life in ice like? - Life cycle of antarctic krill?
Egg, nauplius, calptopsis, larval krill (dependent on under-ice habitat during winter), adult.
What is life in ice like? What is the importance of krill?
Focal point of the southern ocean food web, a single krill swarm can be >450km squared. The southern ocean population amounts to hundred of millions of tonnes.
What is a key challenge of living in the polar benthic zone?
Ice scour, blocks of moving ice can scrape the sea floor and intertidal areas and remove any attached organisms. Major factor in the structure of communities (e.g. pioneer species move in, and deeper water less likely to be affected).
The polar benthos - Arctic?
Large amounts of detritus from high primary production in the summer. Variety of deposit and suspension feeders (polychaetes, soft corals, clams). Predatory fishes and crabs. Kelp along ice-free coasts (Laminaria). Walrus - predate on molluscs.
The polar benthos - Antarctic?
Steep continental shelf - harder substrate. Most frequent scouring events than arctic. Mostly suspension and deposit feeders. Slow paced life processes - slow metabolic rates. Gigantism - often much larger than comparative species in warmer waters.
The polar benthos - Antarctic? What is gigantism a result of?
Slow-growth (because of slow metabolism), increased dissolved oxygen concentrations in polar waters.
Diversity in Polar waters?
Polar water show high endemism. A larger proportion of the species found there won’t e found elsewhere on earth. Endemism in the antarctic is higher than the arctic. Continental shelf differences lead to differences in accessibility between seas.
What fish are adapted to polar waters?
Notothenioids use an antifreeze glycoprotein to reduce the freezing point of their blood (Antarctic - 90% of the fish biomass on the continental shelf)
What polar birds and mammals are adapted to polar waters?
Sea ice is a vital platform. Penguins use to raise young and avoid predators. Walruses use to rest (hauling out). Polar bears use to hunt prey.
