The Arctic consists of ocean
surrounded by continental land masses and islands. The central Arctic Ocean is
ice-covered year-round, and snow and ice are present on land for most of the
year.
The southern limit of the arctic
region is commonly placed at the Arctic Circle (latitude 66 degrees, 32 minutes
North). The Arctic Circle is an imaginary line that marks the latitude above
which the sun does not set on the day of the summer solstice (usually 21 June)
and does not rise on the the day of the winter solstice (usually 21 December).
North of this latitude, periods of continuous daylight or night last up to six
months at the North Pole.
This
region of the planet, north of the Arctic Circle, includes the Arctic Ocean,
Greenland, Baffin Island, other smaller northern islands, and the far northern
parts of Europe, Russia (Siberia), Alaska and Canada.
The
Arctic is a vast, ice-covered ocean, surrounded by tree-less, frozen ground,
that teems with life, including organisms living in the ice, fish and marine
mammals, birds, land animals and human societies.
NSIDC
Map
The
Arctic consists of the Arctic Ocean, bordered by the northern parts of the
mainlands of North American and Eurasia, and their outlying islands. Some of
these islands are mountainous with interior icecaps, such as Greenland and the
northern half of Novaya Zemlaya. Others are low-lying and not glaciated, such as
Wrangel Island and the western islands of the Canadian Arctic.
The Arctic Circle is an imaginary line located at 66º, 30'N latitude, and
as a guide defines the southernmost part of the Arctic. The climate within the
Circle is very cold and much of the area is always covered with ice.
In the mid winter months, the sun never
rises and temperatures can easily reach lows of - 50º F in the higher
latitudes. In the summer months (further south), 24 hours of sunlight a day
melts the seas and topsoil, and is the main cause of icebergs breaking off from
the frozen north and floating south, causing havoc in the shipping lanes of the
north Atlantic.
The
total number of species as well as biological productivity is lower than in more
southern latitudes. Strong surface winds occur resulting in a severe wind-chill,
and abundant drifting snow in winter. Instead of tree growth there is tundra
vegetation that includes grasses, sedges, mosses, lichens, and shrubs...all
low-standing plants that exist on permafrost soils that are frozen solid
throughout most of the year.
In
terms of marine life, because the waters of the Arctic are permanently covered
with a layer of drifting pack ice, sunlight never deeply penetrates the surface
waters to nourish and encourage biological growth. In addition, the water is
vertically stable, offering no upwelling of inorganic salts (like phosphates,
nitrates, and silicates,) without which a rich life in the upper sunlit layers
cannot exist. The result is that the true marine Arctic remains cold and
relatively lifeless. It is only near the land or in the Subarctic where the
pack-ice is seasonal and the waters are warmer and richer in nutrients, that
there is a proliferation of plant and animal life that encompasses the total
spectrum of the food chain from microscopic phytoplankton to walruses and
whales.
Siberia
feels the heat of global warming Russia Today Video
The primary residents of the Arctic include
the Eskimos (Inuits), Lapps and Russians with an overall population (of all
peoples) exceeding two million. The indigenous Eskimos have lived in the area
for over 9,000 years, and many have now given up much of their traditional
hunting and fishing to work in the oil fields and the varied support villages.
Some contemporary occupants of the Arctic and the areas they inhabit are shown
on the map below.
The first explorers of the Arctic were
Vikings. Norwegians visited the northern regions in the 9th century, and Eric
the Red (Icelander) established a settlement in Greenland in 982.
Robert E. Peary
The
northernmost point on the earth's surface is the geographic North Pole, also
known as true north. It's located at 90° North latitude and all lines of
longitude converge at the pole. The earth's axis connects the north and south
poles, as its the line around which the earth rotates. The North Pole is about
450 miles (725 km) north of Greenland in the middle of the Arctic Ocean - the
sea there has a depth of 13,410 feet (4087 meters). In 1909, after
numerous attempts by regional explorers, Robert E. Peary reached the North Pole.
A
magnetic compass does not point toward the true North Pole of the Earth. Rather,
it more closely points toward the North Magnetic Pole of the Earth. The North
Magnetic Pole is currently located in northern Canada. It wanders in an
elliptical path each day, and moves, on the average, more than forty meters
northward each day. Evidence indicates that the North Magnetic Pole has wandered
over much of the Earth's surface in the 4.5 billion years since the Earth
formed. The Earth's magnetic field is created by Earth's partially ionized outer
core, which rotates more rapidly than the Earth's surface.
NASA
JPL, University of Alaska - Fairbanks Satellite: RADARSAT
NASA:
A Short Tour of the Cryosphere Video
Arctic
Climate
The
arctic climate is characterized by high spatial variability, and includes both
polar maritime (influenced by the ocean) and continental (influenced by large
land masses) climate subtypes. The main constant is that the climate in all
arctic areas is affected by the extreme solar radiation conditions of high
latitudes.
For
example, the amount of solar radiation received in summer along the Siberian
arctic coast compares favorably, by virtue of the long period of daylight, with
that in lower middle latitudes. However, the low sun angle (elevation of the sun
above the horizon) means that even minor topographic features, such as low
hills, can cause major differences in climate at the local level by shading.
Even though the Arctic receives a large amount of solar energy in summer, the
high reflectivity (albedo) of snow and ice surfaces keeps absorption of solar
energy low. Therefore, the heat gained during the long summer days is small and
highly dependent on surface properties such as topography and albedo. For
instance, wet tundra and bare ground (with low albedo) absorb more solar
radiation than do high-albedo ice sheets. Similarly, wet snow absorbs more
radiation than dry snow. Solar radiation is small or absent in winter.
The
annual cycle of global radiation (brown line) and surface air temperature (blue
line) at a grid cell location in the central Beaufort Sea. Values were drawn
from the Arctic Meteorology and Climate Atlas grided fields for global
radiation and two-meter air temperature.
Maritime climate conditions
prevail over the Arctic Ocean, coastal Alaska, Iceland, northern Norway and
adjoining parts of Russia. In these areas, winters are cold and stormy. Summers
are cloudy but mild with mean temperatures about 10 degrees Celsius. Annual
precipitation is generally between 60 cm and 125 cm, with a cool season maximum
(largely snowfall) and about six months of snow cover.
The interior, continental
climates have much more severe winters, although precipitation amounts are less.
In these regions, permafrost (permanently frozen ground) is wide-spread and
often of great depth. In summer, only the top one to two meters of ground thaw.
Since the water cannot readily drain away, this "active layer" often
remains waterlogged. Although frost may occur in any month, long summer days
usually provide three months with mean temperatures above 10 degrees Celsius,
and at some stations in the continental interiors temperatures can exceed 30
degrees Celsius.
In winter, arctic weather is
dominated by the frequent occurrence of inversions (when warm air lies above a
colder air layer near the surface). The inversion layer decouples the surface
wind from the stronger upper layer wind. For this reason, surface wind speeds
tend to be lower in winter than one might expect. In summer, inversions are less
frequent and weaker, and arctic weather patterns are dominated by the movement
of low pressure systems (cyclones) across Siberia and into the Arctic Basin.
In many arctic and subarctic
regions, the weather is controlled by semipermanent low pressure systems that
are weakly developed in summer, but stronger in winter. The most important of
these low pressure systems are the Icelandic Low and the Aleutian Low. In
winter, eastern Eurasia is dominated by the semipermanent Siberian High. High
pressure is also prevalent over the Canadian Arctic Archipelago during the cold
season.
NASA
JPL Video: The Big Thaw October 01, 2007 A thick chunk of Arctic sea ice the
size of two states has disappeared. Is it global warming or normal causes? A new
NASA-led study found a 23-percent loss in the extent of the Arctic's thick,
year-round sea ice cover during the past two winters. Between winter 2005 and
winter 2007, the perennial ice shrunk by an area the size of Texas and
California combined. This drastic reduction of perennial winter sea ice is the
primary cause of the fastest-ever sea ice retreat on record this summer.
Scientists say the rapid decline in winter perennial ice was caused by unusual
winds. For more information go to: www.jpl.nasa.gov
Dramatic
Changes In The Arctic
Dramatic
changes have been occurring in the Arctic during the past decade. The change in
the Arctic may play a substantial role in climate change throughout the globe.
These changes include unusual melting of glaciers, sea ice, and permafrost, and
shifts in patterns of rain and snow fall, freshwater runoff, and forest/tundra
growth. The consequences include disrupted wildlife migration patterns, altered
fish stocks, modified agricultural zones, and increased forest fires. These
changes have impacted the lives of Native residents who depend on the
environment for a continuation of their traditional subsistence lifestyle, and
may also have significant impacts on the oil industry, tourism, and shipping
routes. The change in the Arctic may play a substantial role in climate change
throughout the globe.
National
Snow and Ice Data Center Image
Climate
data show that winter temperatures in the northernmost regions of the world have
warmed alarmingly in a very short period. Parts of Alaska and northern Eurasia,
for example, have warmed by nearly 11 degrees Fahrenheit in the winter months
over the past 30 years. Climate evidence from the past four centuries gleaned
from ice cores, lake cores, and tree rings indicates a gentler warming trend
that extends back 400 years. This image shows the winter temperature trend in
the Arctic from 1966 to 1995. The scale is in degrees Celsius per decade. Over
the 20-year period shown, average winter temperatures in central Siberia warmed
by as much as 4°C.
Surface
air temperature anomaly for Barrow, Alaska in April and for Tromso, Norway in
Winter. An anomaly is the difference from a long term average value for the same
season. For Barrow, note the temperatures from 1990 onward are often more than 4
degrees above historical values. For Tromso, note the continuation of warm
temperatures in the 1990's following a period of cold temperatures in the late
1970's and 1980's.
Dramatic
thinning of Arctic ice
NOAA
Graphic
Change
in the age of ice on the Arctic Ocean, compared for September and based on
results from a simulation using drifting buoy data and satellite-derived ice
concentration data (Rigor and Wallace, 2004). Open water (OW) is shown in dark
blue, and the oldest ice is shown in white. The darker green line marks 90% ice
concentration, and the lighter green lines mark ice concentrations of 80, 70,
60, and 50%. This sequence shows that (a) most of the Arctic Ocean was covered
by older, thicker sea ice in September 1988; (b) coincident with a transition to
high-AO conditions in 1989 (Fig. 5), most of the older, thicker sea ice was
rapidly flushed out of the Arctic Ocean through Fram Strait, so that by 1990
only 30% of the Arctic Ocean was covered by older, thicker sea ice; (c) the
relative distribution between older, thicker and younger, thinner sea ice
persisted during the 1990s, in spite of a shift back towards a more neutral AO
in the mid-1990s; and d) the average ice age over the Arctic Ocean apparently
continued to decrease through 2005, with older, thicker ice now limited to the
area north of the Canadian Archipelago.-NOAA
2006 State of the Arctic
Sea ice
extent in September 2005. From NSIDC.
Sea ice
extent in September 2002. From NSIDC.
Melting
Arctic sea ice has shrunk to a 29-year low, significantly below the minimum set
in 2005, according to preliminary figures from the National Snow and Ice Data
Center, part of the University of Colorado at Boulder. NASA scientists, who have
been observing the declining Arctic sea ice cover since the earliest
measurements in 1979, are working to understand this sudden speed-up of sea ice
decline and what it means for the future of Earth's northern polar region.
Polar
ice reflects light from the sun. As this ice begins to melt, less sunlight gets
reflected into space. It is instead absorbed into the oceans and land, raising
the overall temperature, and fueling further melting. This results in a positive
feedback loop called ice albedo feedback, which causes the loss of the sea ice
to be self-compounding. The more it disappears, the more likely it is to
continue to disappear.
credit:NASA
Arctic
Mid-Ocean Ridge Expedition Graphic
Vegetation
of the circumpolar Arctic . The southern boundary of Arctic vegetation is
the treeline. This map gives a good impression of just how closely tied
the tundra biome is to the ocean; 61% of lowland tundra is within 50 km of
sea ice, 80% is within 100 km, and 100% is within 350 km. NOAA 2006 State
of the Arctic
JPL
Video: International Polar Year- March 22, 2007 Glaciers, ice sheets and oceans
at Earth's poles are the subject of the International Polar Year. NASA also
begins work to explore other poles in our solar system.
Data
compiled from The British Antarctic Study, NASA, Environment Canada,
UNEP, EPA and
other sources as stated and credited Researched by Charles
Welch-Updated dailyThis
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