Cadmium in Benthic Foraminifera and Abyssal Hydrography: Evidence for a 41 KYR Obliquity Cycle
- James E. Hansen and
- Taro Takahashi
Published Online: 19 MAR 2013
Copyright 1984 by the American Geophysical Union.
Climate Processes and Climate Sensitivity
How to Cite
Boyle, E. A. (1984) Cadmium in Benthic Foraminifera and Abyssal Hydrography: Evidence for a 41 KYR Obliquity Cycle, in Climate Processes and Climate Sensitivity (eds J. E. Hansen and T. Takahashi), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM029p0360
- Published Online: 19 MAR 2013
- Published Print: 1 JAN 1984
Print ISBN: 9780875904047
Online ISBN: 9781118666036
- Ocean-atmosphere interaction—Congresses
Cd/Ca in fossil benthic foraminifera records the variability of bottom water nutrient concentrations. Detailed records of Cd/Ca in benthic foraminifera have been obtained for (1) 4 cores covering the glacial/interglacial transition in the 2500–3500m water depth range at 42°N in the western North Atlantic and (2) a 285 kyr record at 2925 m on the Rio Grande Rise(32°S). Nutrient concentrations in the deep North Atlantic 18,000 years ago were roughly twice as high as at present. This evidence is consistent with a substantial diminution of North Atlantic Deep Water flux relative to southern water sources, but not with a complete cessation of NADW. It is believed that the formation areas of NADW were ice covered during the last glacial maximum, thereby preventing deep water formation by eliminating large heat losses to the atmosphere. The Rio Grande Rise record shows a strong 41 kyr periodicity during the past 285 kyr. These fluctuations are synchronous with changes in the tilt of the earth's axis, with low Cd/Ca (high relative North Atlantic Deep Water flux) corresponding to tilt maxima. This may be interpreted as evidence that ice-cover of the formation areas of NADW is controlled by high-latitude insolation, with increased obliquity corresponding to higher summer insolation and less ice cover.