Reconstructing the thermal structure of the upper ocean : insights from planktic foraminifera shell chemistry and alkenones in modern sediments of the tropical eastern Indian Ocean

dc.contributor.author Mohtadi, Mahyar
dc.contributor.author Oppo, Delia W.
dc.contributor.author Luckge, Andreas
dc.contributor.author De Pol-Holz, Ricardo
dc.contributor.author Steinke, Stephan
dc.contributor.author Groeneveld, Jeroen
dc.contributor.author Hemme, Nils
dc.contributor.author Hebbeln, Dierk
dc.date.accessioned 2011-09-26T15:29:31Z
dc.date.available 2012-03-10T09:32:46Z
dc.date.issued 2011-09-10
dc.description Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 26 (2011): PA3219, doi:10.1029/2011PA002132. en_US
dc.description.abstract Shell chemistry of planktic foraminifera and the alkenone unsaturation index in 69 surface sediment samples in the tropical eastern Indian Ocean off West and South Indonesia were studied. Results were compared to modern hydrographic data in order to assess how modern environmental conditions are preserved in sedimentary record, and to determine the best possible proxies to reconstruct seasonality, thermal gradient and upper water column characteristics in this part of the world ocean. Our results imply that alkenone-derived temperatures record annual mean temperatures in the study area. However, this finding might be an artifact due to the temperature limitation of this proxy above 28°C. Combined study of shell stable oxygen isotope and Mg/Ca ratio of planktic foraminifera suggests that Globigerinoides ruber sensu stricto (s.s.), G. ruber sensu lato (s.l.), and G. sacculifer calcify within the mixed-layer between 20 m and 50 m, whereas Globigerina bulloides records mixed-layer conditions at ∼50 m depth during boreal summer. Mean calcifications of Pulleniatina obliquiloculata, Neogloboquadrina dutertrei, and Globorotalia tumida occur at the top of the thermocline during boreal summer, at ∼75 m, 75–100 m, and 100 m, respectively. Shell Mg/Ca ratios of all species show a significant correlation with temperature at their apparent calcification depths and validate the application of previously published temperature calibrations, except for G. tumida that requires a regional Mg/Ca-temperature calibration (Mg/Ca = 0.41 exp (0.068*T)). We show that the difference in Mg/Ca-temperatures of the mixed-layer species and the thermocline species, particularly between G. ruber s.s. (or s.l.) and P. obliquiloculata, can be applied to track changes in the upper water column stratification. Our results provide critical tools for reconstructing past changes in the hydrography of the study area and their relation to monsoon, El Niño-Southern Oscillation, and the Indian Ocean Dipole Mode. en_US
dc.description.sponsorship This project was funded by the German Ministry of Education and Research (BMBF project PABESIA) and the “Deutsche Forschungsgemeinschaft” (DFG project HE 3412/15–1). en_US
dc.format.mimetype application/pdf
dc.format.mimetype image/tiff
dc.format.mimetype text/plain
dc.identifier.citation Paleoceanography 26 (2011): PA3219 en_US
dc.identifier.doi 10.1029/2011PA002132
dc.identifier.uri https://hdl.handle.net/1912/4832
dc.language.iso en_US en_US
dc.publisher American Geophysical Union en_US
dc.relation.uri https://doi.org/10.1029/2011PA002132
dc.subject Indian Ocean en_US
dc.subject Mg/Ca en_US
dc.subject Alkenone en_US
dc.subject Oxygen isotopes en_US
dc.subject Planktic foraminifera en_US
dc.subject Thermal structure en_US
dc.title Reconstructing the thermal structure of the upper ocean : insights from planktic foraminifera shell chemistry and alkenones in modern sediments of the tropical eastern Indian Ocean en_US
dc.type Article en_US
dspace.entity.type Publication
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Figure S1: Temperature profiles for the upper 200 m in the study area from the WOA 05, averaged for different basins.
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Figure S2: Salinity profiles for the upper 200 m in the study area from the WOA 05, averaged for different basins.
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Figure S3: Shell Mg/Ca values of G. bulloides (A-C) and G. ruber s.s. (D-E) versus WOA 05 temperatures at their apparent calcification depths with a significant correlation (R2).
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