Cold Facts

Regional measures of temperature and precipitation

Compared with other continents, places in Antarctica where the weather is measured regularly are few and far between (although the placement of automatic weather stations and satellite-based weather measurements are improving coverage of the continent). Of the weather stations that exist, most have relatively short records. As noted in Key factors behind Antarctica’s climate, strict conditions need to be met for weather recordings to be classed as ‘official’ for statistical purposes, and climatologists like to base any statements about the climate of an area (the ‘average weather’ experienced at a locality) on at least 30 years of data (the ’30 year mean’). There are, however, some stations in Antarctica that meet these stringent requirements and allow scientists to build up a picture of how temperature, precipitation, and other climate measures vary across the continent. A few stations have records extending back well beyond 30 years, and these stations are crucial for studies of climate change as described in Climate change: past and future.

Important stations where weather is recorded in the interior of the continent include the Amundsen-Scott station (USA) at the South Pole and the Vostok station (Russia) in East Antarctica. Both stations were established in 1957 as part of the International Geophysical Year. The Amundsen-Scott station is at an elevation of 2900m above sea level and the Vostok station is at 3500m. In addition to being very cold, these stations also represent the extreme of the polar desert climate with very low levels of humidity and precipitation. Weather conditions characteristic of coastal areas of the continent are represented at Halley station (UK) bordering the Weddell Sea, which has been in operation since 1956 and McMurdo station (USA) bordering the Ross Sea, also started in 1956. Also on the coast, the Mawson station (Australia) was set up in 1954 and is the oldest continuously occupied station inside the Antarctic Circle. This station is also notable for the force of the katabatic winds (explained below) that come down off of the high ice sheet: gusts of wind here can sometimes be over 100mph. The Rothera station (UK) provides data on the climate of the Antarctic Peninsula. It is located on the west side of the peninsula at Rothera Point on Adelaide Island and has been in operation since 1975. Peninsula weather recordings have been taken over a longer period of time at Vernadsky station (Ukraine) which was previously a British station called Faraday (the climate data are sometimes referred to as being from Faraday/Vernadsky). There are also other stations along the Peninsula, notably the Palmer station (USA) and the San Martin station (Argentina). There are stations on several islands off the coast of Antarctica that provide data on the weather and climate of the Southern Ocean, for example Signy station (UK) on Signy Island in the South Orkney Islands, first occupied in 1947. Data from a selection of stations are contained in the spreadsheet attached to Student activity 2 below.

Find out the current weather conditions at various stations at:

• the British Antarctic Survey 
• the Antarctic Connection website

Winds

The dominant pattern of atmospheric circulation over Antarctica involves cold air sinking in the interior and then moving away from this area of high pressure towards the edges of the continent. The air that sinks down onto the interior is replaced by air from aloft that has travelled southwards at a higher altitude. This large-scale circulation of air is often referred to as the polar cell. (There is also a polar cell in the Arctic.) As air from the interior moves outwards across Antarctica, it doesn’t travel directly from south to north. Instead, the direction of the air is deflected by the Earth’s rotation to form polar easterlies, meaning that the prevailing wind direction is from east to west across much of the continent. This occurs because the Coriolis Force causes air to be deflected to the left of its ‘pressure gradient path’ (the most direct route from high to low pressure) in the Southern Hemisphere.

Where these easterly winds approach the coast they can reach high velocities. A katabatic wind refers to cold and relatively dense air near the surface moving downhill due to gravity. Across much of the gently sloping ice sheet katabatic winds average about 10 miles per hour; but towards the edges of the continent, slope gradients become steep and air can be funnelled down into coastal valleys causing much higher average velocities. In some places the average annual wind velocity is nearly 50 miles per hour!

Moving northwards, away from the continental interior, the polar easterlies eventually give way to the zone of westerly winds affecting the Southern Ocean. The westerly winds are associated with the low pressure area (circumpolar trough) that surrounds the continent owing to the large temperature difference between cold polar air and milder air from the southern mid-latitudes. The circumpolar trough exists because where warmer air meets the cold polar air (along the polar front) the warmer air is forced upwards, creating lower pressure at sea level and the frequent storm systems that affect the Southern Ocean. Air moving from the mid-latitudes towards the circumpolar trough is deflected to the left by the Coriolis force thereby producing the westerly prevailing winds. The westerly winds and Southern Ocean storm systems affect parts of the Antarctic coastline, the Antarctic Peninsula, and the islands off the coast of Antarctica.

Student activity 1

Location of Research Stations

Use an atlas and/or the following links to annotate a base map of Antarctica to show the location of the Antarctic research stations listed below.

• Antarctic Connection
• Gisdata (Note: at this GIS programme site you can search by key words or place names by clicking in the ‘Query’ box on the binoculars icon. A drop down box will appear showing any locations that include the search term that are within the map data base. Click on the desired location and it will appear on the map. You might have to use the magnifying glass icons to zoom in to see the selected location.)
• Download the base map.

Student activity 3

Write a short essay to explain the differences in climate seen between the different stations. Discuss a variety of different weather variables and consider factors such as latitude, altitude, and proximity to the Southern Ocean in your essay.