A high resolution Late-Glacial isotopic record from Hawes Water, Northwest England: Climatic oscillations: calibration and comparison of palaeotemperature proxies

Abstract

Understanding of the impact of past climate change on the terrestrial environment requires the development of quantitative palaeotemperature indicators that can be readily measured at closely spaced stratigraphic intervals. A high resolution oxygen isotopic record from Hawes Water, Lancashire, UK, reveals a degree of climatic instability that is greater than that recognised in previous isotopic studies of sites from the Atlantic margin of Northwest Europe. Four oscillations in the Late-Glacial interstadial before the onset of the Younger Dryas stadial are marked by sharp negative excursions in the δ 18O record of the carbonate sediments and accompanied by marked changes in chironomid populations and the pollen record. The oscillations are interpreted as cold events: they correlate with events recognised in marine and lacustrine temperature proxy records as well as the isotopic record from the Greenland ice-cores. Results suggest that there has been a significant change in lake water composition since the Late-Glacial but it is argued that the Hawes Water isotopic record, constrained by the results of a study of carbonate precipitation in the modern lake, provides a quantitative record of Late-Glacial temperature change. The 7°C maximum temperature difference inferred from the isotopic data, from the Interstadial optimum to the Younger Dryas stadial, and the magnitude of individual oscillations, compare well with estimates from terrestrial (coleopterid) and marine (diatom sea surface temperature) records: all are significantly greater than the, independently calibrated, 4.2°C change documented from a chironomid record from South Scotland. Such differences need to be resolved if the impacts of climatic events are to be fully understood.