Late Holocene Climate and Environmental Changes: Disentangling Natural and Anthropogenic Signals in Lake Lilandsvatnet (NW Norway)
Abstract
A multi-proxy reconstruction of late Holocene regional climate and environmental history has been produced from the sediments of Lilandsvatnet, a small sub-arctic lake on Vestvågøy, in the Lofoten Islands, Norway. Chronology for the core was developed from two AMS radiocarbon measurements, and five cryptotephra horizons, indicating that the record extends from 125-2500 yrs BP. These five cryptotephra horizons have been identified as; Askja-1875, Hekla-1158, Hekla-1104, OWB-105, and the SN-1 eruption. The tephra horizons support the radiocarbon age model, providing a robust chronology that will allow higher resolution reconstructions from the 2.5 kyr record. Quantitative paleotemperature reconstructions are based on the Uk37 index, relating molecular variations in the C37 alkenones produced by lacustrine haptophytes, to spring lake surface temperatures. A record of compound specific δD values from terrestrial (n-C27-n-C31) and aquatic (n-C17, n-C21, n-C23 and n-C25) lipid n-alkanes will be generated, and the difference between the two sources of n-alkane δD values (ΔDT-A) will serve as a proxy for changes in the effective moisture of the region. Bulk geochemical properties (%TOC, %TN, C/N, δ13C, δ15N) and records of lipid geochemistry (n-alkanes, n-alkenones, n-alkanols, and n-alkanoic acids) serve as proxies for environmental changes in; catchment vegetation/soil stability, organic material sources, primary productivity, and overall ecosystem response to natural climate variability and anthropogenic forcing. This record is also being used to address the timing and impact of human settlement on Vestvågøy. Lilandsvatnet is located adjacent to the location of the major Viking chieftain farm, which existed throughout the Iron Age settlement period. A record of biomarker compounds associated with agricultural land-use practices (pyrogenic PAHs), and human/higher-mammal feces (coprostanol (5β-cholestan-3 β-ol), epicoprostanol (5β-cholestan-3α-ol ), lithocholic acid, and deoxycholic acid) indicate the presence of humans, as well as the presence and species of mammals associated with the development of agriculture. The records provide insight into the environmental alteration associated with the farming, land-use, and animal husbandry practices of the early Viking settlers. The sediments also enable natural environmental changes due to climatic forcing to be distinguished from changes in the local environment due to farming and settlement activities.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMPP31A1830D
- Keywords:
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- 0473 BIOGEOSCIENCES / Paleoclimatology and paleoceanography;
- 1145 GEOCHRONOLOGY / Tephrochronology;
- 1637 GLOBAL CHANGE / Regional climate change;
- 9315 GEOGRAPHIC LOCATION / Arctic region