Preprints
https://doi.org/10.5194/cpd-10-3847-2014
https://doi.org/10.5194/cpd-10-3847-2014
24 Sep 2014
 | 24 Sep 2014
Status: this preprint was under review for the journal CP but the revision was not accepted.

Sensing Seasonality in the Arabian Sea: a coupled δ18O-Mg/Ca approach

W. Feldmeijer, L. J. de Nooijer, G.-J. Reichart, and G.M. Ganssen

Abstract. Millennial scale climate variability punctuates the record of Northern Hemisphere glacials in the form of Dansgaard–Oeschger cycles. The coldest episodes within these cycles have a marked impact on the location of the Inter-tropical Convergence Zone and thereby the intensity and extent of the Asian monsoon system. Arabian Sea oceanography is closely linked to the monsoon cycle and responds rapidly to changes therein. Seasonally varying upwelling intensity, adhesive mixing and the resulting variability on sea surface temperature and salinity, however, make it challenging to precisely reconstruct the behaviour of the Indian monsoon system through the Dansgaard–Oeschger cycles. To reconstruct impact of millennial-scale changes in the monsoon on the Arabian Sea, paired single-specimen Mg/Ca and stable oxygen isotope analyses were performed on three species of planktonic foraminifera from the northern as well as the western Arabian Sea. Mismatches between Mg/Ca- and δ18O-derived temperatures reflect changes in salinity caused by regional variability in the hydrological cycle. Comparison of Mg/Ca-derived temperatures from Globigerinoides ruber, Globigerina bulloides and Neogloboquadrina dutertrei over Heinrich Event 4 and Interstadial 8 allows for reconstructing the seasonal range in temperatures (minima and maxima) and vertical stratification of the water column during these intervals. Results show that Arabian Sea surface water temperatures were lower during the North Atlantic Heinrich Event 4, and that temperatures in the northern and western Arabian Sea differed relatively much. This implies that the north east monsoon (i.e. boreal winter) was enhanced during this interval. In contrast, the summer upwelling related species G. bulloides reveals lower temperatures during Interstadial 8 in the western Arabian Sea, showing an enhanced summer monsoon during the warmers stages of millennial-scale climate variability. Together, these results show that summer and winter monsoon intensities were thus also anti-phased on a millennial scale. An intensified NE monsoon might have contributed to enhanced mixing of surface waters in the northern Arabian Sea.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
W. Feldmeijer, L. J. de Nooijer, G.-J. Reichart, and G.M. Ganssen
 
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Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
W. Feldmeijer, L. J. de Nooijer, G.-J. Reichart, and G.M. Ganssen
W. Feldmeijer, L. J. de Nooijer, G.-J. Reichart, and G.M. Ganssen

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