Early Eocene ocean meridional overturning circulation: the roles of atmospheric forcing and strait geometry
File(s)2021PA004329_Accepted.pdf (6.01 MB)
Accepted version
Author(s)
Type
Journal Article
Abstract
Here, we compare the ocean overturning circulation of the early Eocene (47-56 Ma) in eight coupled climate model simulations from the Deep-Time Model Intercomparison Project (DeepMIP), and investigate the causes of the observed inter-model spread. The most common global meridional overturning circulation (MOC) feature of these simulations is the anticlockwise bottom cell, fed by sinking in the Southern Ocean. In the North Pacific, one model (GFDL) displays strong deepwater formation and one model (CESM) shows weak deepwater formation, while in the Atlantic two models show signs of weak intermediate water formation (MIROC and NorESM). The location of the Southern Ocean deepwater formation sites varies among models and relates to small differences in model geometry of the Southern Ocean gateways. Globally, convection occurs in the basins with smallest local freshwater gain from the atmosphere. The global MOC is insensitive to atmospheric CO2 concentrations from 1x (i.e. 280 ppm) to 3x (840ppm) pre-industrial levels. Only two models have simulations with higher CO2 (i.e. CESM and GFDL) and these show divergent responses, with a collapsed and active MOC, respectively, possibly due to differences in spin-up conditions. Combining the multiple model results with available proxy data on abyssal ocean circulation highlights that strong Southern Hemisphere-driven overturning is the most likely feature of the early Eocene. In the North Atlantic, unlike the present day, neither model results nor proxy data suggest deepwater formation in the open ocean during the early Eocene, while the evidence for deepwater formation in the North Pacific remains inconclusive.
Date Issued
2022-02-19
Date Acceptance
2022-02-14
Citation
Paleoceanography and Paleoclimatology, 2022, 37 (3), pp.1-22
ISSN
2572-4517
Publisher
American Geophysical Union (AGU)
Start Page
1
End Page
22
Journal / Book Title
Paleoceanography and Paleoclimatology
Volume
37
Issue
3
Copyright Statement
© 2022. American Geophysical Union. All Rights Reserved. This is the accepted version of the following article: Zhang, Y., de Boer, A. M., Lunt, D. J., Hutchinson, D. K., Ross, P., van de Flierdt, T., et al. (2022). Early Eocene ocean meridional overturning circulation: The roles of atmospheric forcing and strait geometry. Paleoceanography and Paleoclimatology, 37, e2021PA004329, which has been published in final form at https://doi.org/10.1029/2021PA004329
Sponsor
Natural Environment Research Council (NERC)
Identifier
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021PA004329
Grant Number
NE/P019080/1
Subjects
Science & Technology
Physical Sciences
Life Sciences & Biomedicine
Geosciences, Multidisciplinary
Oceanography
Paleontology
Geology
DEEP-WATER PRODUCTION
STABLE-ISOTOPE RECORD
FOSSIL FISH TEETH
HEAT-TRANSPORT
DRAKE PASSAGE
PLANT DIVERSITY
COMPONENT WATER
SOUTHERN-OCEAN
PACIFIC-OCEAN
SEAWATER SR
Publication Status
Published
Date Publish Online
2022-02-19