Late-Holocene climate in central West Greenland: meteorological data and rock-glacier isotope evidence

Abstract

The central West Greenland climate during the instrumental period since ad 1873 is analysed con cerning interannual and seasonal variations. A marked temperature rise was experienced from ad 1920 to 1930, especially affecting the winter season, after which the mean annual air temperature for ten years was about 3–5°C higher than during the previous period, effectively changing coastal central West Greenland from having the climatological character of a continuous permafrost region to a discontinuous permafrost region. Since then temperatures have gradually decreased, and are now approaching the Little Ice Age level experienced in the late nineteenth century and early twentieth century. Interannual twentieth-century temperature variations since ad 1923 have been substantial (5–15°C) for the winter season, intermediate (2–7°C) for the spring season, and smaller (1–2°C) regarding summer and autumn seasons. During the instrumental period the overall atmospheric circulation, rather than air temperature, appears to be the primary control on precipitation. A unique personal meteorological record for ad 1807–1808 is presented, outlining an early nineteenth-century central West Greenland climate which appears to have been rather warm, variable, stormy and wet compared to the late twentieth century climate. Analyses of the oxygen isotopic composition of ice samples from a ‘Little Ice Age’ glacier-derived rock glacier in Disko Island indicate a mean annual air temperature 2–4°C below present values, during cold intervals of the ‘Little Ice Age’. The potential of rock-glacier ice oxygen isotope data as a means of obtaining information on past climatic change within cold-climate high-relief areas is discussed. The ‘Little Ice Age’ in central West Greenland was presumably characterized by variable climate punctuated by intervals with severe cold winters, short summers, and glacier expansion during the last several centuries. Palaeoclimatic data like these from coastal Greenland represent supplementary information to ice-core data from the central part of the Greenland Ice Sheet.