Holocene climate change in Glen Affric, Northern Scotland : a multi-proxy approach

Abstract

A multi-proxy approach was used to generate a continuous, sensitive Holocene palaeoclimatic record for Glen Affric, north west Scotland. Fluctuations in lake-level were used as a proxy for shifts in precipitation. Rigorous site selection criteria and a new methodology were developed to interpret the lacustrine sediment record in terms of climatically driven changes in water depth by separating (a) allogenic from autogenic sediment inputs and (b) explicitly linking the marginal fen peat system responded to changes in lake-level. The sedimentary record from the lake site, Loch Coulavie, suggests that lake-level has fluctuated repeatedly throughout the Holocene. The comparative magnitude of changes in lake-level defined the relative intensity of shifts in precipitation. Variations in mire surface wetness, as determined through humification analysis, from a series of four hydrologically isolated ombrotrophic blanket mire sites through the east-west trending glen, were used to generate a record of changes in effective precipitation. A reliable radiocarbon chronology obtained from both proxy records allowed the synthesis of these data sets and the definition of Holocene climate change in terms of relative shifts in temperature and precipitation. The data suggests that the early Holocene was more stable in terms of both temperature and precipitation, but that after c. 6200 BP (7200 cal. BP) both temperature and precipitation became highly variable. Several short-lived, abrupt high intensity shifts to increased precipitation occur at c. 6200 BP (7200 cal. BP), c. 5000 BP (5700 cal. BP), c. 3000 BP (3200 cal. BP) and c. 2400 BP (2350 cal. BP). Holocene climatic variability within Glen Affric corresponds to records of changes in North Atlantic oceanic circulation patterns. The predominance of atmospheric systems, such as Atlantic westerlies, may also have controlled spatial climatic variability within the glen, with the periodic establishment of very steep west-east climatic gradients, steeper than at the present day.