Winter Ecology Notes Climateby Mike Link

This image is a set of 44 multi-exposures on the same frame of film taken from January through December of 2003, in Athens, Greece at precisely 16:00:00 Local Meridian Time (the foreground was added later). This analemma represents the motion of the Sun during the course of one year as observed in the late afternoon. As a result of the Earth's tilt about its axis (23.5°) and its elliptical orbit about the Sun, the position of the Sun in the sky changes from one day to the next, even when observed at the same exact time on each day of the year. Furthermore, the figure 8 loop the Sun makes in the sky over a 12-month period (analemma) will be inclined at different angles depending on one's geographical latitude. The latitude of Athens is approximately 38 degrees

Because the ecliptic is tilted to the equator, the sun's motion relative to the stars is due east only in late June and late December. Hence the sun's eastward advance per day is greatest at those times, and least in March and September when the ecliptic crosses the equator slantingly. This means that when the sun is photographed at 8:30 am on different dates of the year, it generally is some minutes ahead of or behind clock time. The effect of this is to give an east-west spread to the pattern of solar images.

Characteristics of Winter

• Reduction in direct sun rays

• Lower energy levels • Snow/Ice• Cold • Wind

Reduction in direct sun rays

Fire and Ice

• Perhaps the most unusual finding was the link between volcanoes and ice by Ben Mason and colleagues.

• In a 300 year study it was found that eruptions were more frequent Dec. – Feb.

• Conclusion that there was an 18% increases in eruptions world wide during northern hemisphere winter.

• Cause is the shift of 10 million tons of seawater as snow, rain, ice on to the continental landmass

• This depresses the N. Pole by 1/10th inch which warps the earth enough to crack the land and move the magma

Global warming?

What’s happening to winter???????

From 1895 to 1970, Minnesota's average temperature rose about one tenth of a degree every decade. But since then it has risen more rapidly,

about half a degree every decade.

The average December-February temperature has been going up more quickly, by about 1 degree per decade since the 1970s. Overnight lows also have risen faster than the

overall average.

At Pokegama Dam near Grand Rapids, between 1887 and 1936 there were an average of 10 nights a year that got below 30 degrees below zero. Since then, the average has been 3 nights a year. In fact, over just the past two decades, the average has been about 1 night a year.

An island around Hibbing and Grand Rapids has experienced an average temperature increase greater than that seen almost anywhere else in the nation.

In that area the average temperature in the past two decades is more than 3 degrees higher than the average during the first part of the 20th century. That kind of small-area difference is hard to explain, climate scientists say. But the general trend of northern Minnesota heating more quickly than southern Minnesota reflects a global pattern in which the Arctic and northern latitudes warm faster.

Shrinking Ice Cap

Based on Studies in Netherland

Winter Ecology Notes Frost, Snow, and Ice

THIS STREAM IS ACTUALLY A TEAR IN THE SOIL FROM THE FROST EXPANSION IN 2003

• In order for it to snow, there has to be enough moisture in the air, and it has to be below 32° F (0° C). If the air is warmer, it will rain or sleet instead. Snow is basically frozen water, but it freezes in the air in very tiny droplets, which makes crystals. There is a lot of air in snow, which means it is much lighter than water or ice. Sometimes there are bigger snowflakes because the tiny droplets stick together before they fall. If the air in the upper atmosphere is above 32° and the air nearer the ground is below 32°, the droplets may start as rain but freeze as they fall into the colder air. This makes sleet.

History can forgive fellows like Tyndall and Bentley for passing off thenucleation process as heavenly hocus-pocus. That they couldn't explain this process is not surprising. Those necks of dust and ash at the heart of every snow crystal are rather petite. Today's snow scientists can tell you that the big ones top out at around one micron—roughly the diameter of a flea's nose hair. Most nuclei are about a tenth that size. Thanks to electron microscopes, scientists can tell you that the main source of these nuclei is clay-rich dust kicked up from the earth's surface. Air pollutants come in a close second, with the balance provided by forest fires, volcanoes, bits of plant matter, wisps of sea salt, a carousel of microorganisms, and the occasional flotsam and jet-sam that sails in from outer space. They can tell you at what temperature and moisture level cloud droplets, or water vapor, will glom onto these nuclei. They can even predict that in every cubic meter (1.3 cubic yards) of the lower atmosphere, where snow forms, you will find anywhere from several hundred to many thousands of aerosol particles floating around up there, just waiting to kick up a snowstorm.

Falling for Snow, Jamie Bastedo, Red Deer Press, Canada, 2003.

CRYSYS - CRYosphere SYStem in Canada

- source of photos/information

Snow crystals

Stellar dendrite

Sectored plates

Hollow Column

Needles

Spatial dendrite

Capped columns

Rimed snowflake

Elevation and precipitation

Snowrollers are molded by strong, gusty surface winds. They look like a rolled-up carpet or small muff and are often hollow. They can be as small as a golf-ball or as large as a 30-gallon drum,.but usually snowrollers are

about 10-12 inches in diameter and a foot wide. Snowrollers appear in open fields under specific weather conditions,

often present following the passage of a strong winter storm. First, the ground surface must have an icy, crusty snow, on which new

falling snow cannot stick. On top of this, about an inch of loose, wet snow, the sticky kind that

makes good snowballs, must accumulate. The optimum air temperature appears to be around freezing, from 28 to 34 F.

Finally, a gusty and strong wind, usually 25 mph or higher, is needed to build the snowroller.

Snowroller formation begins when the wind scoops chunks of snow out of the snowfield, they roll, bounce and tumble, like snowy tumbleweeds,

downwind. Additional snow then adheres to this seed, and the snowroller grows until it finally becomes too large for the wind to push, leaving

behind a characteristic track linking the snowroller's origin to its final resting spot.

By Bryan Yeaton

Snow Rollers

Under clear frosty nights in winter soft ice crystals might form on vegetation or any object that has been chil led below freezing point by radiat ion cooling. This deposit of ice crystals is known as hoar frost and may sometimes be so thick that i t might look l ike snow. The interlocking ice crystals become attached to branches of trees, leafs, hedgerows and grass blades and are one of the most prominent features of a typical 'winter wonderland' day. However, the f ine ' feathers' , 'needles' and 'spines' might also be found on any other object that is exposed to supersaturated air below freezing temperature.

Rime snow – wind sculpted

Rime ice – fog ice

Rime Ice – is essential ly frozen fog. Super-cooled water droplets which are suspended in clouds when temperatures dip below

freezing, wil l freeze instantly when they contact anything solid, such as

a building, road sign, etc.

Hoar frost must not be confused with r ime, which derives from

freezing fog or glaze which forms as a continuos thick layer of ice, rather

than individual frozen droplets.

Hoar Frost

The relat ive humidity in supersaturated air is greater then 100% and the formation of hoar frost is similar to the formation of dew with the difference that the temperature of the object on which the hoar frost forms is well below 0°C, whereas this is not the case with dew. Hoar frost crystals often form intitially on the tips of plants or other objects.

Silver Frost

• Hoar frost might form as liquid dew that has subsequently frozen with a drop in temperature, which is then known as silver frost or white frost. Usually the dew drops do not freeze immediately, even if the air temperature is slightly below zero. Rather they become supercooled dew droplets at first. Supercooled dew will eventually freeze if the temperature falls below about -3°C to -5°C. Hoar frost deposits might also derive by sublimation, when water vapour is forming ice directly on the surfaces concerned. In most cases hoar frost will have formed by a combination of the processes above.

Icicles

Ice cave - Apostles

Ice curtainIce curtains

Icicle formation

• When the snowmelt flows down the roof, the competition between gravity — pulling the water downward — and surface tension — trying to keep the water flow flat — leads to the formation of evenly-spaced ripples along the flow front. These ripples will freeze when and where the surface temperature dips below 0oC (32oF), and the frozen ripples become the icicle roots.

Ridge formation• After a period of continuous

growth, icicles display prominent horizontal ribbing which encircles the icicle to form a series of progressively smaller rings toward the tip. Each ring is separated from those surrounding it by shallow constrictions in the ice. Typically, rings extend outward less than a centimeter (half an inch). During active icicle growth, the rings are initially composed of fragile, thin ice plates growing randomly outward, but the spaces between them are soon filled with downward flowing melt water.

The tip of a growing icicle is primarily liquid water with a pendent drop on the

tip end.

Spin drift

Sastrugi

Sastrugi and frost flowers

Frost flowers

Frost flowers on ice

Fern frost

The mystery circle

• What happens to all that snow? It piles up, gradually compressing in firn, a kind of limbo state for crystals in transition from snow to glacial k In its youthful phase, firn is nothing more than a mass of BB-sized blobs ice riddled with serpentine air spaces. Under increasing pressure from above, air within the ice is steadily squeezed out, while meltwater seeps in, eventually freezing and recrystallizing until the deeper layers of firn are transmuted into true glacial ice. This process can take several years, or even decades depending on the amount of annual dump of snow up on top. One glaciogist boldly calls the end product a "mono-mineralic rock" since, like quartz or diamonds, glacial ice is no more than a consolidated mass of a single mineral—in this case, frozen water.

TransitionsBY Patty Benson

Coated by rime

After wind has tumbled crystals

Rounding evident

Transition view

Small rounded grains

Melting snowpack absorbs water

Melting snowpack with free water

Fractured hail

Pukak or Sugar Snow

• We dug down to rock bottom. "I've saved the best till last, Arthur." I showed him pukak, the large chunky crystals, sometimes called "depth hoar," found at the very base of a mature snowcover. Pukak is an aboriginal term from northwest Alaska; the street term is "sugar snow.“

• Falling for Snow, Jamie Bastedo, Red Deer Press, Canada, 2003.