HR: 08:45h
AN: PP51D-04    [Abstracts]
TI: Alkenone-Based Temperature Reconstruction From Lakes of Southwestern Greenland: Insights from a haptophyte bloom and a new isotopic approach
AU: * D'Andrea, W J
EM: William_DAndrea@brown.edu
AF: Brown University, 324 Brook Street, Providence, RI 02912, United States
AU: Anderson, N J
EM: N.J.Anderson@lboro.ac.uk
AF: Loughborough University, LE11 3TU, Loughborough, 3TU, United Kingdom
AU: Huang, Y
EM: Yongsong_Huang@Brown.edu
AF: Brown University, 324 Brook Street, Providence, RI 02912, United States
AB: We have previously reported high concentrations of alkenones from the laminated sediments of a series of brackish lakes in the Sondre Stromfjord region of southwestern Greenland (67°N, 51°W). Down-core analyses from three of these lakes demonstrate that U^K₃₇ reconstructed from the lake sediments reflects regional temperature variability during the Holocene. Furthermore, comparison of the Greenland U^K₃₇ temperature reconstruction with other high-resolution temperature reconstructions from the North Atlantic reveal spatial patterns which vary over millennial time scales and resemble those associated with the North Atlantic Oscillation. While the Greenland alkenone reconstructions appear robust, the producer organism of lacustrine alkenones (a haptophyte alga) remains unidentified and the growth season and precise habitat of lacustrine haptophytes are unknown. To address these issues, we deployed sediment traps in an alkenone-bearing lake (Braya So) of southwestern Greenland during 2006 and 2007. The automated sediment traps collected discrete seston samples from the lake at ten day intervals. Analysis of the sediment trap material reveals alkenone production in Braya So occurred between mid-June and early July, with more than 50% of alkenone sedimentation occurring over a ten day period in late June. We were present during the haptophyte bloom in June 2007 and filtered water throughout the water column of Braya So to investigate the depth habitat of the alkenone-producing organisms. Alkenone concentration data obtained from the filters elucidate the depth habitat of the haptophytes. U^K₃₇ data from the water column filters, along with direct water column temperature measurements, demonstrate a strong temperature dependence on alkenone unsaturation and allow the first lacustrine in situ U^K₃₇-temperature calibration. In addition, δ¹³C measurements made on alkenones from the water column filters and the sediment trap material provide insight into the role of haptophytes in carbon cycling within Braya So. We captured the suspected alkenone-producer and attempts to culture the organism are under way. New down-core isotopic data, which complement the Holocene U^K₃₇ reconstruction, will also be presented. These include bulk sediment δ¹³C and δ¹⁵N, as well as δ D reconstructed from individual alkenones; a record generated using a newly developed alkenone separation technique.
DE: 0424 Biosignatures and proxies
DE: 0458 Limnology (1845, 4239, 4942)
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting