Stable isotope and Mg/Ca ratio of sediment core GeoB12610-2

• Main Authors: Rippert, Nadine, Baumann, Karl-Heinz, Pätzold, Jürgen
• Format: Dataset
• Language: English
• Published: PANGAEA 2015
• Subjects: AGE; AWI_Paleo; Calculated from Mg/Ca ratios (Anand et al.; 2003); Calculated from Mg/Ca ratios (Dekens et al. 2002); DEPTH; sediment/rock; GeoB12610-2; Globigerinoides ruber sensu stricto; Magnesium/Calcium ratio; δ18O; Gravity corer (Kiel type); ICP-OES; Inductively coupled plasma - optical emission spectrometry; M75/2; M75/2_97-2; Mass spectrometer Finnigan MAT 251; Meteor (1986); Neogloboquadrina dutertrei; Paleoenvironmental Reconstructions from Marine Sediments @ AWI; Pemba Channel; Sea surface temperature; annual mean; standard deviation; SL; Thermocline temperature; Thermocline water temperature; Antarctic; Indian; Southern Ocean; The Antarctic; Antarc*; Antarctica; Planktonic foraminifera
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.841927; https://doi.org/10.1594/PANGAEA.841927

To reconstruct the still poorly understood thermocline fluctuations in the western tropical Indian Ocean, a sediment core located off Tanzania (GeoB12610-2; 04°49.00'S, 39°25.42'E, 399 m water depth) covering the last 35 ka was analysed. Mg/Ca-derived temperatures from the planktonic foraminifera Globigerinoides ruber (white) and Neogloboquadrina dutertrei indicate that the last glacial was ~2.5 °C colder in the surface waters and ~3.5 °C colder in the thermocline compared with the present day. The depth of the thermocline and thus the stratification of the water column were shallower during glacial periods and deepened during the deglaciation and Holocene. The increased inflow of Southern Ocean Intermediate Waters via 'ocean tunnels' appears to cool the thermocline from below, leading to a similarity between the thermocline record of GeoB12610-2 with the Antarctic EDML temperature curve during the glacial. With rising sea level and the corresponding greater inflow of Red Sea Waters and Indonesian Intermediate Waters, the proportion of Southern Ocean Intermediate Water within the South Equatorial Current is reduced and, by Holocene time, the correlation to Antarctica is barely traceable. Comparison with the eastern Indian Ocean reveals that the thermocline depth reverses from the last glacial to present.