Ice in an interesting ecological factor. When a river or a lake is frozen to its bottom during a long winter, plants and animals attached to the bottom are killed. Fish and other active swimmers may also be also killed, but many will escape as the water becomes filled with ice crystals. Some escape to neighboring salt water bodies, but freshwater animals might not survive if forced into salt water for a long time.
Another ecological effect is that islands where surrounding water normally provides a good barrier against predators that cannot swim are invaded and the entire island population of, for instance hares, becomes food for foxes and other animals of prey. When water becomes solid, new roads of migration are opened up for animals.
Glaciers are massive bodies of living ice — ice is plastic under pressure. In cold winters with much snow, a glacier becomes thicker and the increased pressure on the glacier ice below causes the glacier to move down through the valley where it resides. At the lower front end of the glacier its huge tongue advances and pushes and scrapes away everything in its path. Farms and farm houses are sometimes overrun, but the people have time to get away. Local population near a glacier will know from their fathers and grandfathers about the destruction caused by their glacier in the past.
During a series of cold, snowy years a glacier may reach the valley it drains into. The glacier does not stop but runs down that valley and until a mountain side stops it. This is a dangerous situation, since the glacier will dam any river found at the valley bottom. When the glacier melts and the ice-dammed lake bursts the natural disaster is a fact. In my database there are many descriptions from historical sources about such events over the last two millennia.
But there is no steady state in Nature. Cold periods were followed by warm periods in larger and smaller cycles during the past 4 billion years. The same is true of all natural processes. During the warm periods glaciers shrink.
The illustration below shows how the Aletsch glacier (also pictured above) in the Alps — the largest glacier in Europe — advanced during cold and snow rich periods (blue tongues) during the years 25-2000 CE. To the right, notice the glacier's longest extension 1350, 1660 and 1840. On the left axis, its extension is noted for some selected years.
The red tongues in the illustration represent the warm and dry periods, when the Aletsch glacier retreated up to 3000 m. The industrial revolution with its change from farming to industry powered by electricity, coal and petroleum took place 1750-1840 when the climate became colder. From the end of it until today the Great Aletsch glacier has retreated 3000 m due to a warmer climate.
To a geologist this picture also shows a quasi-rhythmicity between cold and warm periods in our time that cannot be explained by human interference. In my opinion it is urgent to extend climate studies beyond 1750 and beyond the meteorological domain to find out the causes of the oscillations between cold and warm periods. If we make a parallel with contemporaneous modelling of global warming with its time perspective of less than 200 years and used the year AD 200 as starting point, the climate modellers would state that mankind would be frozen to death 200 years later, at AD 400. This illustration shows that extrapolation cannot be used because the air temperature is not linear over time.
Based on my database, an analysis of the breakup of ice in river Daugava/Düna/Dvina in central Latvia 1530-1852 shows that climate extremes are companions in time. When a winter is very cold with late ice breakup, it is close in time to a warm winter with very early ice breakup. These extreme events occur with about 100 years in between.
The following table shows the amount of information in the Ice subregister of the database. If you are interested in the climate fluctuations 100,000-600,000 years BCE, you can also check the subregister Climate.
|ICE subregister (pages)||1402|
|43 entries of which most data in these 20|