Ole Humlum, The University Courses on Svalbard (UNIS), Box 156, N-9170 Longyearbyen, Norway

oleh@unis.no

Polar regions are recognized as key areas for monitoring global climatic changes. In this poster observed variations in the spatial pattern of seasonal surface temperatures within the Antarctic continent are analyzed for 10-yr periods since the International Geophysical year in 1957, where many Antarctic meteorological stations were established. For the full period up to 2000, there have been only small Antarctic continental net annual temperature changes, although there have been significant seasonal and regional variations. In the early part of the period warming prevailed for most regions of Antarctica, especially during the summer season. Since 1990 a cooling tendency has prevailed, affecting especially spring and autumn and to a lesser degree, the summer, while a slight warming has characterized the winter. Observed Antarctic surface air temperature records 1960-1998 reveal periods of persistent (multi-year) and geographically extensive temperature trends towards cooling in the interior and warming in the coastal regions. The spatial and seasonal patterns of these trends are, however, not quite simple and appear to change with time; that is, the temperature relationship between specific locations is not temporally consistent. Within the Antarctic Peninsula a warming trend has persisted, with exception of the spring season. Cooling has been modest in coastal East Antarctic regions, but pronounced at the Amundsen-Scott Base and at the South Pole. By this, a Peninsula-Central Antarctic temperature opposition apparently has prevailed during much of the late 20th century. This situation has been difficult to simulate by Global Climate Models and is not yet fully understood. Observational evidence, however, suggests the present warmer conditions in the Antarctic Peninsula to be caused by enhanced zonal westerlies around the Antarctic continent, associated with the present cooling over central Antarctica. This causes warmer conditions to prevail in peripheral regions, such as the Peninsula, penetrating north into the zone of enhanced westerlies.