On the estimation of deep Atlantic ventilation from fossil radiocarbon records. part I: modern reference estimates
Citable URI
https://hdl.handle.net/1912/28631As published
https://doi.org/10.1175/JPO-D-20-0153.1DOI
10.1175/JPO-D-20-0153.1Keyword
Atlantic Ocean; Abyssal circulation; Tracers; Inverse methodsAbstract
Radiocarbon dates of fossil carbonates sampled from sediment cores and the seafloor have been used to infer that deep ocean ventilation during the last ice age was different from today. In this first of two companion papers, the time-averaged abyssal circulation in the modern Atlantic is estimated by combining a hydrographic climatology, observational estimates of volume transports, Argo float velocities at 1000 m, radiocarbon data, and geostrophic dynamics. Different estimates of modern circulation, obtained from different prior assumptions about the abyssal flow and different errors in the geostrophic balance, are produced for use in a robust interpretation of fossil records in terms of deviations from the present-day flow, which is undertaken in Part II. We find that, for all estimates, the meridional transport integrated zonally and averaged over a hemisphere, ⟨Vk⟩, is southward between 1000 and 4000 m in both hemispheres, northward between 4000 and 5000 m in the South Atlantic, and insignificant between 4000 and 5000 m in the North Atlantic. Estimates of ⟨Vk⟩ obtained from two distinct prior circulations—one based on a level of no motion at 4000 m and one based on Argo float velocities at 1000 m—become statistically indistinguishable when Δ14C data are considered. The transport time scale, defined as τk=Vk/⟨Vk⟩, where Vk is the volume of the kth layer, is estimated to about a century between 1000 and 3000 m in both the South and North Atlantic, 124 ± 9 yr (203 ± 23 yr) between 3000 and 4000 m in the South (North) Atlantic, and 269 ± 115 yr between 4000 and 5000 m in the South Atlantic.
Description
Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 51(6),(2021): 1842–1872, https://doi.org/10.1175/JPO-D-20-0153.1.
Collections
Suggested Citation
Marchal, O., & Zhao, N. (2021). On the estimation of deep Atlantic ventilation from fossil radiocarbon records. part I: modern reference estimates. Journal of Physical Oceanography, 51(6), 1842–1872.Related items
Showing items related by title, author, creator and subject.
-
On the estimation of deep Atlantic ventilation from fossil radiocarbon records. Part II: (in)consistency with modern estimates
Marchal, Olivier; Zhao, Ning (American Meteorological Society, 2021-08-01)Measurements of radiocarbon concentration (Δ14C) in fossil biogenic carbonates have been interpreted as reflecting a reduced ventilation of the deep Atlantic during the last ice age. Here we evaluate the (in)consistency ... -
Agulhas leakage into the Atlantic estimated with subsurface floats and surface drifters
Richardson, Philip L. (2006-12-02)Surface drifters and subsurface floats drifting at depths near 800 m were used to study the pathways of warm salty Indian Ocean water leaking into the South Atlantic that is a component of the upper limb of the Atlantic ... -
Estimate of heat flux and its temporal variation at the TAG hydrothermal mound, Mid-Atlantic Ridge 26°N
Goto, Shusaku; Kinoshita, Masataka; Schultz, Adam; von Herzen, Richard P. (American Geophysical Union, 2003-09-17)From August 1994 to March 1995, three 50-m-high vertical thermistor arrays designated “Giant Kelps” (GKs) were deployed around the central black smoker complex (CBC) at the TAG hydrothermal mound, Mid-Atlantic Ridge ...