A World Meteorological Organization (WMO) committee of experts announced on March first, new records for the highest temperatures recorded in the Antarctic Region. The results are part of continuing efforts to expand a database of extreme weather and climate conditions throughout the world.
A temperature of +19.8°C (67.6°F) measured at British Antarctic Survey’s Signy Research Station on Borge Bay on the South Orkney Islands on 30 January 1982 is a record for the Antarctic region (defined as “all land and ice shelves south of 60°S”). The committee reached this conclusion after examining temperature data from the Antarctic since records began in the late 1950s.
So what caused temperatures at Signy to reach levels more typical of a summer day in the UK than those experienced across much of the Antarctic?
BAS meteorologist Dr John King, a member of the WMO expert committee, explains: “Summer temperatures at Signy can sometimes reach double figures, but this event in January 1982 is pretty unusual. Weather systems in the South Atlantic were bringing exceptionally warm subtropical air southwards towards Signy that year. As this air moved south across the cold Southern Ocean it cooled at low levels but remained very warm above 1 km altitude. This warm air was brought back towards the surface as the air flowed over the mountainous Coronation Island just to the north of Signy – a phenomenon known as a föhn wind. Although average temperatures at Signy have been rising at around 0.2°C per decade, the highest temperature we’ve measured since January 1982 has been 13.8°C, showing just how exceptional that event was.”
The committee also confirms that the temperature of +17.5°C (63.5°F) measured at the Argentine station of Esperanza in the Antarctic Peninsula on 24 March 2015 is a record for the Antarctic continent. It also reports an observation of -7.0°C (19.4°F), made on 28 December 1980 at an automatic weather station in Adélie Land is a record for the Antarctic plateau above 2500 m elevation.
The lowest temperature yet recorded by ground measurements for the Antarctic Region, and for the whole world, was −89.2°C (-128.6°F) at Vostok station on 21 July 1983.
“Global temperatures are rising and we are witnessing big changes in the polar regions such as the recent rapid reduction of Arctic summer sea ice. Determining temperature extremes for a region is important as it sets a baseline against which climate variability and change can be measured. BAS currently monitors temperature and a range of other climate variables at its five permanent research stations and at a number of remote automatic weather stations scattered across the sub Antarctic islands and the Antarctic Peninsula. These data are shared with the international climate research community and underpin studies of Antarctic climate variability and change”, added Dr. King.
Spanning 14 million km2 (roughly twice the size of Australia), the Antarctic is cold, windy and dry. The average annual temperature ranges from about −10°C on the Antarctic coast to −60°C at the highest parts of the interior. Its immense ice sheet is up to 4.8km thick and contains 90% of the world’s fresh water, enough to raise sea level by around 60 metres were it all to melt. The Antarctic Peninsula (the northwest tip near to South America) is among the fastest warming regions of the planet, almost 3 C over the last 50 years. The majority of glaciers along the west coast of the Antarctic Peninsula have retreated in the last 50 years with most of these showing accelerated retreat in the last 12 years.
The WMO investigations also serve to improve the quality of observations through the careful analysis of observation practices and proper equipment selection.
“The Antarctic and the Arctic are poorly covered in terms of weather observations and forecasts, even though both play an important role in driving climate and ocean patterns and in sea level rise. Verification of maximum and minimum temperatures help us to build up a picture of the weather and climate in one of Earth’s ‘final frontiers’, says Michael Sparrow, a polar expert with the WMO co-sponsored World Climate Research Programme.
Full details of the assessment are in the issue of Eos Earth and Space Science News of the American Geophysical Union (AGU)