GDGT and alkenone flux in the northern Gulf of Mexico: Implications for the TEX86 and UK137 paleothermometers

Paleoceanography
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Abstract

The TEX86 and math formula molecular biomarker proxies have been broadly applied in down-core marine sediments to reconstruct past sea surface temperature (SST). Although both TEX86 and math formula have been interpreted as proxies for mean annual SST throughout the global ocean, regional studies of GDGTs and alkenones in sinking particles are required to understand the influence of seasonality, depth distribution and diagenesis on downcore variability. We measure GDGT and alkenone flux, as well as the TEX86 and math formula indices in a 4-year sediment trap time series (2010-2014) in the northern Gulf of Mexico (nGoM), and compare these data with core-top sediments at the same location. GDGT and alkenone fluxes do not show a consistent seasonal cycle, however the largest flux peaks for both occurs in winter. math formula co-varies with SST over the 4-year sampling interval, but the math formula-SST relationship in this data set implies a smaller slope or non-linearity at high temperatures when compared with existing calibrations. Furthermore, the flux-weighted math formulavalue from sinking particles is significantly lower than that of underlying core-top sediments, suggesting preferential diagenetic loss of the tri-unsaturated alkenone in sediments. TEX86 does not co-vary with SST, suggesting production in the subsurface upper water column. The flux-weighted mean TEX86 matches that of core-top sediments, confirming that TEX86 in the nGoM reflects local planktonic production rather than allochthonous or in-situ sedimentary production. We explore potential sources of uncertainty in both proxies in the nGoM, but demonstrate that they show nearly identical trends in 20th century SST, despite these factors.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title GDGT and alkenone flux in the northern Gulf of Mexico: Implications for the TEX86 and UK137 paleothermometers
Series title Paleoceanography
DOI 10.1002/2016PA003032
Volume 31
Issue 12
Year Published 2016
Language English
Publisher American Geophysical Union
Publisher location Washington, D.C.
Contributing office(s) St. Petersburg Coastal and Marine Science Center
Description 15 p.
First page 1547
Last page 1561
Other Geospatial Northern Gulf of Mexico