Reconstructing the upper water column thermal structure in the Atlantic Ocean
Article first published online: 16 SEP 2013
©2013. American Geophysical Union. All Rights Reserved.
Volume 28, Issue 3, pages 503–516, September 2013
How to Cite
2013), Reconstructing the upper water column thermal structure in the Atlantic Ocean, Paleoceanography, 28, 503–516, doi:10.1002/palo.20050., , , and (
- Issue published online: 11 OCT 2013
- Article first published online: 16 SEP 2013
- Accepted manuscript online: 5 SEP 2013 11:48AM EST
- Manuscript Accepted: 30 AUG 2013
- Manuscript Revised: 29 AUG 2013
- Manuscript Received: 21 JAN 2013
- deep-dwelling foraminifera;
- oxygen minimum
The thermal structure of the upper ocean (0–1000 m) is set by surface heat fluxes, shallow wind-driven circulation, and the deeper thermohaline circulation. Its long-term variability can be reconstructed using deep-dwelling planktonic foraminifera that record subsurface conditions. Here we used six species (Neogloboquadrina dutertrei, Globorotalia tumida, Globorotalia inflata, Globorotalia truncatulinoides, Globorotalia hirsuta, and Globorotalia crassaformis) from 66 core tops along a meridional transect spanning the mid-Atlantic (42°N to 25°S) to develop a method for reconstructing past thermocline conditions. We estimated the calcification depths from δ18O measurements and the Mg/Ca-temperature relationships for each species. This systematic strategy over this large latitudinal section reveals distinct populations with different Mg/Ca-temperature relationships for G. inflata, G. truncatulinoides, and G. hirsuta in different areas. The calcification depths do not differ among the different populations, except for G. hirsuta, where the northern population calcifies much shallower than the southern population. N. dutertrei and G. tumida show a remarkably constant calcification depth independent of oceanographic conditions. The deepest dweller, G. crassaformis, apparently calcifies in the oxygen-depleted zone, where it may find refuge from predators and abundant aggregated matter to feed on. We found a good match between its calcification depth and the 3.2 ml/l oxygen level. The results of this multispecies, multiproxy study can now be applied down-core to facilitate the reconstruction of open-ocean thermocline changes in the past.