HR: 17:15h
AN: PP44A-05    [Abstracts]
TI: Warm Times and Cold Times During the Last 2000 Years Reconstructed from Icelandic Lake and Marine Sediments
AU: * Geirsdottir, A
EM: age@hi.is
AF: Institute of Earth Sciences & Dept. of Earth Sciences, University of Iceland, Askja, Sturlugata 7, Reykjavik, 101, Iceland
AU: Miller, G H
AF: INSTAAR and Dept. of Geological Sciences, University of Colorado, Campus Box 450, Boulder, CO 80309-0450, United States
AU: Flowers, G E
AF: Department of Earth Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
AU: Olafsdottir, S
EM: saeadiso@hi.is
AF: Institute of Earth Sciences & Dept. of Earth Sciences, University of Iceland, Askja, Sturlugata 7, Reykjavik, 101, Iceland
AU: Olafsdottir, K B
EM: kbo@hi.is
AF: Institute of Earth Sciences & Dept. of Earth Sciences, University of Iceland, Askja, Sturlugata 7, Reykjavik, 101, Iceland
AU: Axford, Y
EM: yaxford@buffalo.edu
AF: Institute of Earth Sciences & Dept. of Earth Sciences, University of Iceland, Askja, Sturlugata 7, Reykjavik, 101, Iceland
AU: Axford, Y
EM: yaxford@buffalo.edu
AF: Department of Geology, University at Buffalo, 876 Natural Sciences Complex, Buffalo, NY 14260, United States
AB: Holocene lacustrine records and their synchronization with available marine records from around Iceland provide compelling evidence for the alternating influences of the warm Irminger Current, and the cold East Greenland Current during Holocene times. Here we present data for the past 2000 years from two lakes in Iceland; Haukadalsvatn, a non-glacial lake in northwest Iceland; and Hvitarvatn, a glacial lake east of Langjokull glacier in Central Iceland. Physical and chemical proxies (magnetic susceptibility, TOC, biogenic silica, sedimentation rate, ice rafted debris) in the lake sediments were analyzed at subdecadal resolution. Overall, the interval from 2000 to 800 BP is characterized by a covariant pattern of biogenic silica and TOC, indicating relatively stable climate. A moderate Medieval Warm Period shows up in our records between 1200 and 800 BP. About 800 BP, a sharp increase in TOC coincides with a decline in biogenic silica. This decoupled pattern between the two proxies intensifies after 600 BP, ending about 100 BP. The δ¹³C of total organic carbon in Haukadalsvatn sediments during this interval (800 to 100 BP) indicates that carbon in the lake sediments was dominantly from terrestrial sources, most likely brought into the lake by soil erosion during storm events. The timing of most intense soil erosion coincides with historically documented sea-ice intensity off the coast of Iceland during this time. The ice rafted debris record from Hvitarvatn indicates that the height of the Little Ice Age (LIA) was between 1750 - 1850 AD. Glacier simulations constrained by our proxies from Hvitarvatn suggest Langjokull attained its maximum LIA volume around 1840 AD with a second advance around 1890 AD; the magnitude of glacier advance suggests summer temperature depression 1-2°C lower than present. The two outlet glaciers terminating in Hvitarvatn, Nordurjokull and Sudurjokull, advanced slowly into the lake, occupying their maximum lake area (4-6 km²) in the late 19th century, and retreated comparatively rapidly in the mid- to late 20th century. Newly obtained climate proxy records from the shelf southwest and northwest of Iceland also reflect these centennial scale climate fluctuations, and a similar picture is emerging from lake-sediment records in north Iceland (Axford et al., this volume). Coherency between the lacustrine records, sea-ice variability, and records of marine productivity suggests a strong maritime influence on the terrestrial climate of Iceland.
DE: 1600 GLOBAL CHANGE
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting