||The Arctic Gradients
||The Arctic Ecosystem is a jigsaw.
The picture is made up of many parts. The ecosystems that we normally
recognise, the different habitats, are each systems that have interconnected
parts and processes. But, as you have seen, they are not completely
self-contained and isolated from each other. They also change gradually
along distinct environmental gradients. It is these physical gradients
which determine the structure and function of the ecosystems, their
dynamics and their responses to the ever changing environment.
||What are these gradients? On land,
in freshwaters and in the sea, a dominant gradient is the rise in
temperature from North to South, but other large scale physical
gradients have major effects on the structure and function of the
Sunrise over Eyjafjord, Akureyri Iceland.
The mountains shelter the valley from the wind. Photo: Jonas Allansson
On land, from the coast to inland areas, the oceanic-continental
gradient in climate gives increasing seasonal range of temperature
and decreasing rain and snowfall. Ranges of mountains, especially
near the coast, intercept clouds and cause major local increase
in rain and snowfall. The mountains also provide sharp local altitudinal
gradients in temperature.
Freshwater systems are dominated by topography (slope and steepness),
determined mainly by geology. The mountain glaciers and rivers
flow sharply to the sea or spread over the vast continental areas
of flat tundra.
Marine systems grade from the shore, through the tidal zone,
over theextensive,gently sloping continental shelf and down to
the deeper ocean floor, with its submerged valleys, troughs and
mountains - a mirror image of the land surface (see
figure 7a and figure 7b).
How do these systems respond to the environmental gradients?
How do the structures and processes change? How do the pieces
of the jigsaw change? Examine the dynamics more closely as you
move along the gradients of the three subsystems - the land (terrestrial),
the freshwater (hydrological), and the marine.