High-resolution reconstruction of Polar Ural glacier mass balance for the last millennium

Abstract

Our ultimate objective is to study the mass-balance variations of Polar Ural glaciers during the last millennium. We use mass-balance data for two glaciers between 1957 and 1981, climate data obtained by instrumental observations during the 20th century, and tree-ring data compiled for the last 1000 years. Because there is a high correlation between measured glacier mass-balance and climate variables, we reconstruct glacier mass balance for the 20th century using regression equations. Similarly, we use regression equations relating measured climatic variables to tree-ring widths to reconstruct glacier mass balance for the last millennium. According to our reconstructions, the most extensive period of negative mass balance occurred in the late 10th/ early 11th century AD, which corresponds to the Medieval Warm Period. A prolonged period of positive glacier mass balance began after the mid-11th century, a time commonly accepted as the onset of the Little Ice Age. This cooling period has three maxima, the last from the early 17th to mid-19th century. Until the beginning of the 20th century, cumulative mass balance over the last millennium varied between ±8 m w.e. However, glacier mass balance in the second half of the 20th century is lower than it has been for the past millennium, and cumulative mass balance is now -10 m w.e. Polar Ural glaciers are important indicators of regional climate change and should be incorporated into a worldwide glacier-monitoring programme.