A biomarker perspective on dust, productivity, and sea surface temperature in the Pacific sector of the Southern Ocean. (1st May 2017)

• Record Type: Journal Article
• Authors: Jaeschke, Andrea; Wengler, Marc; Hefter, Jens; Ronge, Thomas A.; Geibert, Walter; Mollenhauer, Gesine; Gersonde, Rainer; Lamy, Frank
• Is Part Of: Geochimica et cosmochimica acta. Volume 204(2017)
• Page Start: 120
• Page End: 139
• Publication Date: 2017-05-01
• Subjects: Biomarkers -- Southern Ocean -- Dust -- 230Th -- GDGT -- U37K′ -- TEX86; Geochemistry -- Periodicals; Meteorites -- Periodicals; Géochimie -- Périodiques; Météorites -- Périodiques; Geochemie; Astrochemie; Electronic journals; 551.905
• DOI: 10.1016/j.gca.2017.01.045
• Languages: English
• ISSNs: 0016-7037

Abstract

Abstract: In this study, we present a new multiproxy data set of terrigenous input, marine productivity and sea surface temperature (SST) from 52 surface sediment samples collected along E–W transects in the Pacific sector of the Southern Ocean. Allochthonous terrigenous input was characterized by the distribution of plant wax n -alkanes and soil-derived branched glycerol dialkyl glycerol tetraethers (brGDGTs). 230 Th-normalized burial of both compound groups were highest close to the potential sources in Australia and New Zealand and are strongly related to lithogenic contents ( 232 Th), indicating common sources and transport. Detection of both long-chain n -alkanes and brGDGTs at the most remote sites in the open ocean strongly suggests a primarily eolian transport mechanism to at least 110°W, i.e. by prevailing westerly winds. Two independent organic SST proxies were used, the U 37 K ′ based on alkenones, and the TEX86 based on isoprenoid GDGTs. Both, U 37 K ′ and TEX86 indices show robust relationships with temperature over a temperature range between 0.5 and 20 °C, likely implying different seasonal and regional imprints on the temperature signal. Alkenone-based temperature estimates best reflect modern summer SST in the study area when using the polar calibration of Sikes et al. (1997). In contrast, TEX86 -derived temperatures may reflect a subsurface signal rather than surface. 230 Th-normalized burial of alkenones is highest close to the Subtropical Front and is positively related to the deposition of lithogenic material throughout the study area. In contrast, highest isoGDGT burial south of the Antarctic Polar Front may be largely controlled by diatom blooms, and thus high opal fluxes during austral summer.