Factors Affecting Arctic Weather and Climate

Just like other areas on Earth, weather and climate in the Arctic depends on a lot of variables, including latitude that affects how much energy is received from the sun, and the distribution land and water. Arctic climates are highly varied. Individually the factors that affect Arctic climate are important. However, they also interact with each other to produce weather patterns and climate feedbacks, which have effects both within the Arctic region and far beyond the Arctic.

One way of thinking about Arctic climate is to consider the Arctic Energy Budget, or the balance of energy into and out of the Arctic region. Over the course of the year, the atmosphere moves energy northward into the Arctic. Energy escapes by moving through the atmosphere and then to outer space. But energy can be added to the atmosphere from the ocean and land or can flow into the ocean and land. These energy flows vary throughout the year. Learn more about these factors:

Latitude and Sunlight

Effect of Latitude on Sunlight Angle

The amount of sunlight hitting the Earth's surface is affected by the tilt of the Earth and its atmosphere.
Credit: Peter Halasz.

If the axis of Earth's rotation were perfectly perpendicular to the plane of Earth's orbit around the sun, the duration of daylight in every 24-hour period would be uniform across the globe: 12 hours of daylight and 12 hours of darkness. Earth's axis is tilted, however, and depending on where the Earth is on its annual trip around the sun, the Northern Hemisphere is either tilted towards the sun (summer), or tilted away from the sun (winter). Whatever the season in the Northern Hemisphere, the Southern Hemisphere is in the opposite season.

Differences in the length of daylight and darkness linked to earth tilt and the seasons are smallest near the Equator, and greatest at the poles, where daylight and darkness last months. Depending on latitude, the seasonal difference in the duration of light and dark is greater (closer to the pole) or smaller (closer to the Equator).

At the North Pole, the sun sets on the autumnal equinox (around September 21) and stays below the horizon until the following vernal equinox (around March 21). The sun rises to its maximum height at the summer solstice, usually around 21 June, but depending on the year can also occur on 20 or 22 June. Because the sun stays above the horizon round the clock in summer, the Arctic is sometimes called the land of midnight sun.

How much of the sun's energy reaches the ground in a particular region depends on the angle and duration of sunlight, affected by Earth's tilt, as well as factors such as cloud cover and elevation.

Pressure

Synoptic ChartSynoptic Chart Key

Example of a synoptic chart for 28 August 1980. —Credit: M. Serreze and R. Barry (1988).

Meteorologists look at changes in air pressure to figure out how air masses are moving and predict how weather will change.

Surface air pressure, or atmospheric pressure, is caused by the weight of a column of air directly above a point on the Earth. At high elevations such as the top of mountains, there is less air above the Earth's surface than at lower elevations such as sea level, so atmospheric pressure is lower at the top of a mountain than at sea level. Most weather maps show sea level pressure, which is the atmospheric pressure at sea level. Weather maps show atmospheric pressure using lines called isobars, which are similar to contours on a topographic map. Just as topographic contours show hills, basins, ridges and valleys, isobars show areas of high pressure (called anticyclones) and low pressure (called cyclones). These are formed by the circulation of the atmosphere around the Earth, and by movement of air upwards and downwards.

Changes in atmospheric pressure can indicate what the weather will be like. A decrease in pressure indicates an approaching low-pressure system (cyclone), which is associated with cloudy and wet conditions. An increase in pressure indicates an approaching high-pressure system (anticyclone), which is associated with clear and dry conditions. Over longer periods of time, weather maps show patterns where high pressure and low pressure features are common. The names of these patterns often reflect their location. In the Arctic, the common features are the Aleutian Low, Siberian High, Icelandic Low and Beaufort Sea High. Scientists look at the strength of these patterns to study changes in atmospheric circulation, and how these change are related to changes in temperature, precipitation and winds.

Temperature

Temperature is often the first thing you read in a weather report, and can help you decide what clothes to wear, what activities to plan, and what gear to bring when heading outside.

Air temperature is a measure of the amount of energy held in the air. Warm air has more internal energy than cooler air. Temperature can be reported using several different scales. In the United States, the Fahrenheit scale is the most common. Internationally and in science, people use the Celsius scale.

Just like other regions of the Earth, temperatures in the Arctic tend to rise during the day, when sunlight warms the ground, and fall at night. Arctic temperatures are warmer in summer, when there is more sunlight, and colder in winter, when the region is dark.

Scientists also use temperature for monitoring changes in climate. Long-term measurements of air temperatures over many years are important for scientists to track climate change. Temperature data show that the Arctic has warmed strongly over the past several decades.

Geography

Atlantic and Arctic Ocean Circulation

In this schematic drawing of North Atlantic and Arctic Ocean circulation, red arrows represent relatively warm water from lower latitudes entering the Arctic, while blue arrows show the export of colder water from the Arctic. Shaded white shows the average area covered by sea ice. Click for larger image.
Credit: G. Holloway, Institute of Ocean Sciences, Sidney, British Columbia.

Much of the Arctic region stays warmer than scientists would expect based only on latitude. That warmth comes from both the poleward transport of energy by the atmosphere and the poleward the ocean port of energy by the ocean. The ocean effect is most pronounced in the north Atlantic and Scandinavia.  Water has a high heat capacity, meaning that it takes a lot of energy to change its temperature. This is one reason that coastal areas tend to have mild climates: the ocean keeps them cool during the summer and warm during the winter. Land, in contrast has a lower heat capacity, so it heats up quickly during the day and cools down as soon as the sun goes down.

Ocean currents bring heat from warmer regions into the Arctic Ocean. In the Atlantic Ocean, a current called the Gulf Stream brings warm water up along the coast of North America and across the North Atlantic Ocean towards northern Europe. The Gulf Stream keeps places like Norway and the island of Svalbard much warmer than other places at similar latitudes in the Arctic.

But the sea ice covering the Arctic Ocean acts like a lid, preventing heat from the ocean from escaping to warm the atmosphere. That means that the air above the ice can get bitterly cold—deep below freezing—while the water underneath remains much warmer—never getting colder than the freezing point.

Wind

Wind is the movement of air between regions of high pressure to regions of low pressure. The larger the difference between high and low pressure (shown by closely spaced isobars on a weather map), the faster the wind. Wind speed and direction is also influenced by other factors, including the Coriolis force and surface friction. The Coriolis force, caused by the rotation of the Earth, changes the direction of the wind. In the northern hemisphere, the Coriolis force deflects the wind to the right, so that winds circulate in a clockwise direction around high-pressure regions, and counterclockwise around low-pressure regions. The opposite occurs in the southern hemisphere. Surface friction is caused by the movement of air across land and ocean surfaces. Friction slows the wind.

Winds in the Arctic can vary a lot in strength, but they are typically light. Winds tends to be stronger in the Russian Arctic, where there are more storms, than in the Canadian Arctic. Winds can be strong in the Atlantic sector of the Arctic where there are many storms. Strong temperature inversions form in winter, which slow winds near the ground. Temperature inversions are where air at the surface is cooler than the air above. These inversions disconnect the surface air from the air above.

Although Arctic winds are typically light, strong gales that can reach hurricane strength can occur and last several days. In the winter, these strong winds scour the snow from exposed areas and form large snow drifts in sheltered areas. Strong winds increase the wind chill factor. Wind chill refers to the cooling effect of any combination of temperature and wind, expressed as the loss of body heat in watts per square meter of skin surface. The body has a very thin layer of still air immediately adjacent to it called the boundary layer that helps to insulate the body from heat loss. As wind speed increases, the thickness of the boundary layer diminishes, and the rate of heat loss from the body increases.

Humidity

How Coriolis Force Affects Global Wind

The Coriolis force explains why winds circulate around high and low pressure systems as opposed to blowing in the direction of the pressure gradient. The following figure shows how wind is deflected in each hemisphere.

Air is a mixture of gases, which includes mostly nitrogen, oxygen, but also some argon, carbon dioxide and water vapor (water in its gas form). Humidity refers to the amount of water vapor in air.  All air contains at least some water vapor, but the amount of water vapor changes a lot from place to place and from time to time. The amount of water vapor in air can increase when water evaporates from land and water surfaces, and as plants respire. Humidity decreases when water vapor condenses to form very small drops of liquid water, forming clouds or growing to become rain drops. Evaporation and condensation happen all the time. Sometimes more water is evaporating into the atmosphere, sometimes more water is condensing out of the atmosphere, and sometimes as much water evaporates into the atmosphere as condenses out of it. When evaporation is the same as condensation at a location in the atmosphere, scientists call the air at this point saturated.

There are several measures of the amount water vapor in air. Relative humidity is one measure often used by meteorologists and TV weather reporters. Relative humidity is the ratio of water vapor in the air to the saturated water vapor content of the air.

Overall, humidity in the Arctic atmosphere is low. Colder air has a lower capacity to hold water vapor than does arm air, and in some places, Arctic air is as dry as air in the Sahara Desert. Humidity tends to be higher over the oceans and in coastal areas and in summer, when water vapor evaporates from the relatively warm ocean surfaces. Humidity is lower over land areas, such as Canada, where there is less water to evaporate. In winter, humidity is very low because surface temperatures are very cold and very little water evaporates into the atmosphere. At this time of year, sea ice covers much of the Arctic Ocean, preventing evaporation from ocean water. However, in areas where there is no sea ice cover in areas, there can be a lot of evaporation and fog can form, making the ocean look as if it is steaming.

Clouds

Clouds are made of tiny water droplets or ice crystals that have condensed onto tiny pieces of sea salt, dust, smoke, or other particles in the air. Clouds have two major effects on weather and climate. Clouds reflect sunlight, which can keep surface temperatures cool. However, they also trap heat close to the Earth's surface, which keeps temperatures warmer. Which one of these processes wins out depends on how thick the clouds are, and a number of other factors, including cloud type and thickness, the magnitude of the solar radiation, and the albedo of the underlying surface.

For the Arctic as a whole, the cloudiest months are in summer, when the sea ice melts away and exposes open water in the Arctic Ocean. That open water adds more moisture to the air, helping to increase cloud cover. Cloud cover is least extensive in December and January, when the ice cover is at its thickest and temperatures are lowest. However, in the Atlantic sector, clouds are extensive year round.

Precipitation

Precipitation is water that is deposited on Earth's surface from the atmosphere. Although we generally think of precipitation as rain or snow, hail, dew, hoar frost are also forms of precipitation. Precipitation is part of the hydrological cycle. It supplies water for plants to grow, soaks into the soil and feeds river and lakes, which eventually drain to the ocean. Water from plants, soil, and the oceans evaporates back into the atmosphere. There it forms clouds and returns to the Earth surface as precipitation.

Over much of the Arctic, precipitation amounts are low. Some areas are called polar deserts and receive as little precipitation as the Sahara desert. However, the Atlantic sector of the Arctic, between Greenland and Scandinavia is an exception. Storms forming in the Atlantic Ocean bring moisture up into this area, especially in winter.

Almost all precipitation in the central Arctic Ocean and over land falls as snow in winter. However, rain can occur on rare occasions during winter in the central Arctic ocean when warm air is transported into this region. Snow also falls in summer. More than half of the precipitation events at the North Pole in summer are snowfall. Over the warmer Atlantic sector, snow is very rare in summer.

Last updated: 4 May 2020