Changes in the oceanic 13C/ 12C ratio during the last 140 000 years: High-latitude surface water records

• Published in: Palaeogeography, palaeoclimatology, palaeoecology Vol. 50; no. 1; pp. 217 - 240
• Main Authors: Labeyrie, Laurent D., Duplessy, Jean Claude
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1985; Elsevier
• Subjects: Continental interfaces, environment; Ocean, Atmosphere; Sciences of the Universe
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/S0031-0182(85)80014-6

Detailed records of the carbon and oxygen isotopic ratios of Neogloboquadrina pachyderma are compared between nine high-latitude sediment cores, from the Northern and Southern Hemispheres, covering the last 140 000 yrs. The strong analogies between the δ 13C records permit to define a δ 13C stratigraphic scale, with three clear cut transitions simultaneous with the oxygen isotopic transitions 6/5 (125 kyrs.), 5/4 (65 kyrs.), and 2/1 (13 kyrs.). The δ 13C records of N. pachyderma in the high-latitude cores, which follow the changes in δ 13C of the surface water TCO 2 near areas of deep water formation present trends similar to the benthic foraminifera δ 13C records in cores V19–30 and M12-392, although amplitudes of the isotopic shifts are different. This implies that a large part of the observed variations represents global changes in the carbon distribution between biosphere and ocean. The 13C/ 12C ratios of N. pachyderma in the North Atlantic cores display larger regional variations at 18 kyrs. B.P. than at present. To explain these differences, we have plotted the 18 kyrs. B.P. δ 13C values of N. pachyderma from 17 cores distributed N of 40°N. Comparison with published surface water temperature distribution at 18 kyrs. B.P. indicates that a strong divergent cyclonic cell, centered approximatively 55°N and 15°W, was active during most of the last ice-age maximum This hydrology, analogous to the present Weddell Sea, explains the published evidences of bottom water formation, if located on the northern flank of the gyre, and the strong polar front on the southern flank, probable location of intermediate water formation.