User:StephenHudson/Climate of the Arctic
The Climate of the Arctic is characterized broadly by long, cold winters and short, cool summers. There is a large amount of variability in climate across the Arctic, but all regions experience extremes of solar radiation in both summer and winter. Some parts of the Arctic are covered by ice (sea ice, glacial ice, or snow) year-round, and nearly all parts of the Arctic experience long periods with some form of ice on the surface. Average January temperatures range from about −40 to 0 °C (−40 to +32 °F), and winter temperatures can drop below −50 °C (−58 °F) over large parts of the Arctic. Average July temperatures range from about −10 to +10 °C (14 to 50 °F), with some land areas occasionally exceeding 30 °C (86 °F) in summer.
The Arctic consists of ocean that is nearly surrounded by land. As such, the climate of much of the Arctic is moderated by the ocean water, which can never have a temperature below −2 °C (28 °F). In winter, this relatively warm water keeps the North Pole from being the coldest place in the Northern Hemisphere, and it is also part of the reason that Antarctica is so much colder than the Arctic. In summer, the presence of the near-by water keeps coastal areas from warming as much as they might otherwise, just as it does in temperate regions with maritime climates.
Overview of the Arctic
Depending on the context, there are different definitions of the Arctic, some more appropriate for certain uses than others. The most widely-used definition, the area north of the Arctic Circle, is appropriate for astronomical and some geographic uses since this defines the area where, on the June solstice, the sun does not set. However, in a context of climate, it often makes sense to use a definition based on elements of the climate. The two most widely-used definitions in this context are the area north of the northern tree line, and the area in which the average temperature of the warmest month is less than 10 °C (50 °F). Since the former cannot be defined over water, this article will use the latter definition; the two are nearly coincident over most land areas.[2]
To discuss the climate in any detail, this definition of the Arctic must be further divided into regions, within which the main aspects of the climate do not vary much. This article defines four main regions:
- The Arctic Basin includes the Arctic Ocean within the average minimum extent of sea ice (see map above), except as discussed below.
- The Canadian Archipelago includes the large and small islands, except Greenland, on the Canadian side of the Arctic, and the waters between them.
- Greenland includes the entire island of Greenland, but its ice sheet and ice-free coastal regions must be discussed separately.
- The ice-free seas include the Arctic waters that are not covered by sea ice in late summer, including the Hudson Bay, Baffin Bay, the Davis, Denmark, and Bering Straits, and the Labrador, Norwegian, Greenland, Barents, Kara, Laptev, Chukchi, and Bering Seas.
Other islands and the parts of mainland North America and Eurasia that lie within the Arctic will be discussed along with the regions above to which they are adjacent. Moving inland from the coast over mainland North America and Eurasia, the moderating influence of the Arctic Ocean quickly diminishes, and the climate transitions from Arctic to subarctic, generally in less than 500 kilometers (300 mi), and often over a much shorter distance.
History of Arctic climate observation
Due to the lack of major population centers in the Arctic, weather and climate observations from the region tend to be widely spaced and of short duration compared to the midlatitudes and tropics. Though Western explorers have been prodding the Arctic nearly continuously for the last half millennium now (Vikings explored parts of the Arctic over a millennium ago, and small numbers of people have been living along the Arctic coast for much longer), scientific knowledge about the region was slow to develop; the large islands of Severnaya Zemlya, just north of the Taymyr Peninsula on the Russian mainland, were not discovered until 1913, and not mapped until the early 1930s (Serreze and Barry, 2005).
Early exploration
Much of the early exploration of the Arctic was motivated by the search for the Northwest and Northeast Passages. Sixteenth- and seventeenth-century expeditions were largely driven by traders in search of these shortcuts between the Atlantic and the Pacific. These forays into the Arctic did not venture far from the North American and Eurasian coasts, and were unsuccessful at finding a navigable route through either passage.
National and commercial expeditions continued to expand the detail on maps of the Arctic through the eighteenth century, but largely neglected other scientific observations. Expeditions from the 1760s to the middle of the 1800s were also led astray by attempts to sail north because of the belief by many at the time that the ocean surrounding the North Pole was ice-free. These early explorations did provide a sense of the sea ice conditions in the Arctic and occasionally some other climate-related information.
By the early 1800s some expeditions were making a point of collecting more detailed meteorological, oceanographic, and geomagnetic observations, but they remained sporadic. Beginning in the 1850s regular meteorological observations became more common in many countries, and the British navy implemented a system of detailed observation (Serreze and Barry, 2005). As a result, expeditions from the second half of the nineteenth century began to provide a picture of the Arctic climate.
Early observing efforts
The first major effort to study the meteorology of the Arctic was the First International Polar Year (IPY) in 1882 to 1883. Eleven nations provided support to establish twelve observing stations around the Arctic. The observations were not as wide-spread or long-lasting as would be needed to describe the climate in detail, but they provided the first cohesive look at the Arctic weather.
In 1884 the wreckage of the Jeanette, a ship abandoned three years earlier off Russia's eastern Arctic coast, was found on the coast of Greenland. This caused Fridtjof Nansen to realize that the sea ice was moving from the Siberian side of the Arctic to the Atlantic side. He decided to use this motion by freezing a specially-designed ship, the Fram, into the sea ice and allowing it to be carried across the ocean. Meteorological observations were collected from the ship during its crossing from September 1893 to August 1896. This expedition also provided valuable insight into the circulation of the ice surface of the Arctic Ocean.
In the early 1930s the first significant meteorological studies were carried out on the interior of the Greenland Ice Sheet. These provided knowledge of perhaps the most extreme climate of the Arctic, and also the first suggestion that the ice sheet lies in a depression of the bedrock below (now known to be caused by the weight of the ice itself).
Fifty years after the first IPY, in 1932 to 1933, a second IPY was organized. This one was larger than the first, with 94 meteorological stations, but World War II delayed or prevented the publication of much of the data collected during it (Serreze and Barry 2005). Another significant moment in Arctic observing before World War II occured in 1937 when the USSR established the first of over 30 North-Pole drifting stations. This station, like the later ones, was established on a thick ice floe and drifted for almost a year, observing the atmosphere and ocean along the way.
Cold-War era observations
Following World War II, the Arctic, lying between the USSR and North America, became a front line of the Cold War, inadvertently and significantly furthering our understanding of its climate. Between 1947 and 1957, the United States and Canadian governments established a chain of stations along the Arctic coast known as the Distant Early Warning Line (DEWLINE) to provide warning of a Soviet nuclear attack. Many of these stations also collected meteorological data.
The Soviet Union was also interested in the Arctic and established a significant presence there by continuing the North-Pole drifting stations. This program operated continuously, with 30 stations in the Arctic from 1950 to 1991. These stations collected data that are valuable to this day for understanding the climate of the Arctic Basin. This map shows the location of Arctic research facilities during the mid 1970s and the tracks of drifting stations between 1958 and 1975.
Another benefit from the Cold War was the acquisition of observations from United States and Soviet naval voyages into the Arctic. In 1958 an American nuclear submarine, the Nautilus was the first ship to reach the North Pole. In the decades that followed submarines regularly roamed under the Arctic sea ice, collecting sonar observations of the ice thickness and extent as they went. These data became available after the Cold War, and have provided evidence of thinning of the Arctic sea ice. The Soviet navy also operated in the Arctic, including a sailing of the nuclear-powered ice breaker Arktika to the North Pole in 1977, the first time a surface ship reached the pole.
Scientific expeditions to the Arctic also became more common during the Cold-War decades, sometimes benefiting logistically or financially from the military interest. In 1966 the first deep ice core in Greenland was drilled at Camp Century, providing a glimpse of climate through the last ice age. This record was lengthened in the early 1990s when two deeper cores were taken from near the center of the Greenland Ice Sheet. Beginning in 1979 the Arctic Ocean Buoy Program (the International Arctic Buoy Program since 1991) has been collecting meteorological and ice-drift data across the Arctic Ocean with a network of 20 to 30 buoys.
Satellite era
The end of the Soviet Union in 1991 led to a dramatic decrease in regular observations from the Arctic. The Russian government ended the system of drifting North Pole stations, and closed many of the surface stations in the Russian Arctic. Likewise the United States and Canadian governments cut back on spending for Arctic observing as the perceived need for the DEWLINE declined. As a result, the most complete collection of surface observations from the Arctic is for the period 1960 to 1990 (Serreze and Barry, 2005).
The extensive array of satellite-based remote-sensing instruments now in orbit has helped to replace some of the observations that were lost after the Cold War, and has provided areal coverage that was impossible without them. Routine satellite observations of the Arctic began in the early 1970s, expanding and improving ever since. A result of these observations is a thorough record of sea-ice extent in the Arctic since 1979; the decreasing extent seen in this record,[3][4] and its possible link to anthropogenic global warming, has helped increase interest in the Arctic in recent years. Today's satellite instruments provide routine views of not only cloud, snow, and sea-ice conditions in the Arctic, but also of other, perhaps less-expected, variables, including surface and atmospheric temperatures, atmospheric moisture content, winds, and ozone concentration.
Civilian scientific research on the ground has certainly continued in the Arctic, and it is getting a boost from 2007 to 2009 as nations around the world increase spending on polar research as part of the third International Polar Year. During these two years thousands of scientists from over 60 nations will co-operate to carry out over 200 projects to learn about physical, biological, and social aspects of the Arctic and Antarctic.[5]
Modern researchers in the Arctic also benefit from computer models. These pieces of software are sometimes relatively simple, but often become highly complex as scientists try to include more and more elements of the environment to make the results more realistic. The models, though imperfect, often provide valuable insight into climate-related questions that can't be tested in the real world. They are also used to try to predict future climate and the effect that changes to the atmosphere caused by humans may have on the Arctic and beyond. Another interesting use of models has been to use them, along with historical data, to produce a best estimate of the weather conditions over the entire globe during the last 50 years, filling in regions where no observations were made. These reanalysis datasets help compensate for the lack of observations over the Arctic.
Solar radiation
Almost all of the energy available to the Earth's surface and atmosphere comes from the sun in the form of solar radiation. Variations in the amount of this energy from the sun reaching different parts of the Earth are a principal driver of global and regional climate. Averaged over a year, latitude is the most important factor determining the amount of solar radiation reaching the top of the atmosphere; the incident solar radiation decreases smoothly from the Equator to the poles. This variation leads to the most obvious observation of regional climate: temperature tends to decrease with increasing latitude.
Over time periods of days to months, other factors may become more important than latitude. The most important additional factor is the length of time during each day that the sun is above the horizon; this is determined by latitude and season and is shown in the top plot at right. The 24-hour days found near the poles in summer result in a large daily-average solar flux reaching the top of the atmosphere in these regions. In fact, on the June solstice 36% more solar radiation reaches the top of the atmosphere over the course of the day at the North Pole than at the Equator (Serreze and Barry, 2005). Contrast this large amount of incident sunlight with the six months from the September to March equinoxes when the North Pole receives no sunlight at the top of the atmosphere, and the extremes of solar radiation found in the Arctic become apparent.
The lower plot at right shows how the length of civil twilight varies with latitude and season. This is an estimate of the period each day when it is light enough outside to do things without artificial lighting. While mostly irrelevant to climate, it is relevant to people's perception of a place since it is roughly what we see as the length of the day. In this figure it is clear that the duration of continuous darkness in the Polar regions is significantly less than the duration of continuous light, by about one month at the poles. The twilight results from the atmosphere scattering sunlight to an observer at the surface even though there is no sunlight incident at the top of the atmosphere above the observer.
The climate of a region depends on more than just how much solar radiation reaches the top of the atmosphere; if it did not, there would be no variation in climate from east to west. Among other things, the amount of sunlight reaching the surface, and the amount that the surface absorbs are also important. Variations in the frequency of cloud cover can cause significant variations in the amount of solar radiation reaching the surface at locations with the same latitude. Changes in surface conditions, such as the appearance or disappearance of snow or sea ice, can cause large changes in the surface albedo, the fraction of the solar radiation reaching the surface that is reflected rather than absorbed.
Winter
Spring
Summer
Autumn
Temperature
Arctic Basin
Canadian Archipelago
Greenland
Ice-free seas
Precipitation
Arctic Basin
Canadian Archipelago
Greenland
Ice-free seas
Ice
Sea ice
Greenland ice sheet
Other glaciers and ice caps
Pressure
Climate change and global warming
See also
References
- National Aeronautics and Space Administration. Arctic Sea Ice Continues to Decline, Arctic Temperatures Continue to Rise In 2005. Accessed 6 September 2007.
- National Snow and Ice Data Center. Cryospheric Climate Indicators: Sea Ice Index. Accessed 6 September 2007.
- National Snow and Ice Data Center. NSIDC Arctic Climatology and Meteorology Primer. Accessed 19 August 2007.
- Przbylak, Rajmund, 2003: The Climate of the Arctic, Kluwer Academic Publishers, Norwell, MA, USA, 270 pp.
- Serreze, Mark C. and Roger Graham Barry, 2005: The Arctic Climate System, Cambridge University Press, New York, 385 pp.
- United States Central Intelligence Agency, 1978: Polar Regions Atlas, National Foreign Assessment Center, Washington, DC, 66 pp.
- USSR State Committee on Hydrometeorology and Environment, and The Arctic and Antarctic Research Institute (chief editor A.F. Treshnikov), 1985: Atlas Arktiki (Atlas of the Arctic), Central Administrative Board of Geodesy and Cartography of the Ministereal Council of the USSR, Moscow, 204 pp (in Russian with some English summaries). [Государственный Комитет СССР по Гидрометеорологии и Контролю Природной Среды, и Ордена Ленина Арктический и Антарктический Научно-Исследовательский Институт (главный редактор Трешников А.Ф.), 1985: Атлас Арктики, Главное Управление Геодезии и Картографии при Совете Министров СССР, Москва, 204 стр.]