Unit 8 Test
An Arctic Ecosystem
Rising atmospheric CO le2els from burning fossil fuels and other anthropogenic activity contributes to a
warming of the Earth. Rising atmospheric CO levels from burning fossil fuels and other anthropogenic
activity therefore contributes to a warming of the Earth.
The North Pole may become up to 8°C warmer by the end of the 21 century unless we slow down
greenhouse gas emissions.
As arctic snow and ice melt, the darker land and ocean surfaces that are revealed absorb more of the
sun’s energy, increasing arctic warming. In the arctic, a greater fraction of the extra energy received at the
surface due to increasing concentrations of greenhouse gases goes directly into warming the
atmosphere, whereas in the tropics, a greater fraction goes into evaporation. The depth of the
atmospheric layer that has to warm in order to cause warming of near –surface air is much shallower in
the arctic than in the tropics, resulting in a larger arctic temperature increase. As warming reduces the
extent of sea ice, solar heat absorbed by the oceans in the summer is more easily transferred to the
atmosphere in the winter, making the air temperature warmer than it would be otherwise. Because heat is
transported to the arctic by the atmosphere and oceans, alterations in their circulation patterns can also
increase arctic warming.
The sub-Arctic regions of Canada (e.g., Churchill, Manitoba) contain a wide variety of both aquatic and
terrestrial ecosystems, each characterized by different abiotic and biotic factors. In the high Arctic, near
the communities of Resolute and Devon Island, much of the terrestrial environment is dominated by
tundra. However, even at very high latitudes, there are both freshwater (rivers, ponds, lakes) and marine
(Arctic ocean) habitats.
A distinguishing feature of Arctic aquatic ecosystems is ice.
Marine mammals that need to maintain a 37 degree body temp have a thick layer of insulating blubber
just under the skin.
Animals that generate their own internal heat through metabolism are called endotherms (meaning “inside
heat”). For the most part, this is restricted to the so-called “warm-blooded” vertebrates — that is,
mammals and birds.
Unlike mammals and birds, fishes do not regulate their body temperatures internally, so they usually have
the same internal temperature as the surrounding water. Animals such as fishes (and amphibians,
reptiles, and invertebrates) that rely on environmental sources of heat are called ectotherms (meaning
Water breathing animals (e.g. molluscs, crustaceans, fish) have a gill structure that brings blood to an
interface with the water (external environment) and the blood (internal environment), with a thin layer of
gill cells in between. Any heat generated through metabolic processes is quickly lost at the gills, so that
blood temperature is equal to the temperature of the external or ambient environment.
The north has been called “the land of the midnight sun” because the sun does not set at summer
solstice, and at winter solstice the sun does not climb above the horizon.
Some animals hibernate over the winter, while some stay active and search for scarce food. Some ectothermic animals, by contrast, can’t avoid freezing and survive numerous freeze-thaw cycles
over many years (e.g., Woolly Caterpillar).