Biomarker evidence of Holocene climate and cryosphere variability; results from a 171m, annually laminated, sediment core from the Adélie coast, Antarctica (IODP Expedition 318)

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http://abstractsearch.agu.org/meetings/2012/FM/PP13C-08.html
Author(s): Bendle, James A.; Seki, O.; Kawamura, K.; Willmott, Veronica; Schouten, Stefan; Sangiorgi, F.; McKay, Robert M.; Riesselman, C. R.; Dunbar, R. B.
Author Affiliation(s): Primary:
University of Birmingham, Geography, Earth and Environmental Sciences, Birmingham, United Kingdom
Other:
Hokkaido University, Japan
Alfred Wegener Institute for Polar and Marine Research, Germany
NIOZ, Netherlands
Utrecht University, Netherlands
Victoria University of Wellington, New Zealand
University of Otago, New Zealand
Stanford University, United States
Volume Title: AGU 2012 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2012; American Geophysical Union 2012 fall meeting, San Francisco, CA, Dec. 3-7, 2012. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The Southern Ocean remains the least studied region on Earth with respect to Holocene climate variability. The few Antarctic proximal marine sedimentary records available tend to be short, low resolution, and discontinuous. However, sediments recently recovered from the Adélie drift during IODP Expedition 318 present a new opportunity to study East Antarctic Holocene climatic evolution, at a resolution that facilitates direct comparison with ice-cores. Expedition 318 recovered 171m of Holocene laminated diatom ooze from site U1357B. The sediments represent continuous Holocene accumulation up to the present day (based on 89 AMS 14C dates) and are characterized by 2-6cm thick, light/dark laminae couplets, interpreted as seasonal biogenic production and accumulation events. We present the results of initial biomarker analyses: fatty acid δD and TEX86 measurements on lipid extracts from paired light/dark laminae throughout the Holocene. The C18 fatty acid is assumed to represent an integrated signal from the algal precursors and thus surface water conditions. The δDC18-FA values show no consistent offset between the light and dark laminae, and values become isotopically heavier on average through the Holocene (ca. -220 to 140ppm), in line with declining insolation at 65°S. Superimposed on this trend are millennial scale isotopic excursions of ca. 20 to 60ppm, including a clear excursion coeval with an increase in grain size in U1356B and the late Holocene climate "optimum" between 6 and 3 kyr, inferred from East Antarctic ice-cores. δDC18-FA shows no clear relationship with TEXL86 sea-surface temperature estimates, which display pronounced early variability and relative warmth from 11.2 to 10.4 ka (0 to 6.5 °C, average ca. 3.5 °C), but almost no change after 10.4 ka, as cold, stable SSTs (average ca. 2 °C) persist through the rest of the Holocene. We explore the potential controls on the δDC18-FA record and suggest the influence of isotopically depleted meltwater from the proximal ice-sheet (additive to a salinity effect) and/or upwelling could account for the millennial scale variability. The next steps are to ground-truth the proxies in this unique archive and to exploit the paleoclimatic information encoded in the abundant algal sterol compounds, the higher plant waxes and to apply compound-specific δ13C as well as additional δD measurements.
Year of Publication: 2012
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Cenozoic; Climate change; Cores; Expedition 318; Holocene; IODP Site U1357; Integrated Ocean Drilling Program; Marine sediments; Paleo-oceanography; Paleoclimatology; Paleosalinity; Paleotemperature; Quaternary; Sediments; Southern Ocean
Coordinates: S662448 S662448 E1402531 E1402531
Record ID: 2015005631
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