Terrestrial impact of abrupt changes in the North Atlantic thermohaline circulation: Early Holocene, UK

• Main Authors: Marshall, JD, Lang, B, Crowley, SF, Weedon, GP, van Calsteren, P, Fisher, EH, Holme, R, Holmes, JA, Jones, RT, Bedford, A, Brooks, SJ, Bloemendal, J, Kiriakoulakis, K, Ball, JD
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: GEOLOGICAL SOC AMERICA, INC 2007
• Subjects: abrupt climate change; holocene; 8200 event; 9.3 ka event; stable isotopes; lacustrine record; CLIMATE-CHANGE; BRITISH-ISLES; BP EVENT; RECORD; OCEAN; DELTA-O-18; ATMOSPHERE; GREENLAND; MODEL; Greenland; Greenland ice cores; North Atlantic; North atlantic Thermohaline circulation; Northeast Atlantic
• Online Access: http://discovery.ucl.ac.uk/140732/

Abrupt cooling events are features of Holocene climate and may recur in the future. We use lake records from Hawes Water, NW England, to quantify the impact of two prominent early Holocene climatic events. Subdecadal oxygen isotope records from sedimentary carbonate (delta O-18(c)), dated using thermal ionization mass spectrometry (TIMS) U-series analyses, provide evidence for abrupt cold events, lasting similar to 50 and similar to 150 yr at 9350 and 8380 yr ago, which correlate with the 9.3 ka and 8.2 ka events recognized in Greenland ice cores. At Hawes Water, mean July air temperatures, inferred from chironomid assemblages, decreased by similar to 1.6 degrees C during each event. Calculations show that the isotopic excursions were dominantly caused by decreases in the isotopic composition of meteoric precipitation (delta O-18(p)) by similar to 1.3 parts per thousand; this is interpreted as a direct downstream response to cooling and freshening of northeast Atlantic surface water by melting ice sheets. Intermediate in magnitude between events observed in Greenland and central Europe, the effects are consistent with a partial shutdown of the North Atlantic thermohaline circulation.