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Title: Can the Salt-Advection Feedback Be Detected in Internal Variability of the Atlantic Meridional Overturning Circulation?

Abstract

Evidence for the assumptions of the salt-advection feedback in box models is sought by studying the Atlantic meridional overturning circulation (AMOC) internal variability in the long preindustrial control runs of two Earth system models. The first assumption is that AMOC strength is proportional to the meridional density difference between the North Atlantic and the Southern Oceans. The model simulations support this assumption, with the caveat that nearly all the long time-scale variability occurs in the North Atlantic density. The second assumption is that the freshwater transport variability by the overturning at the Atlantic southern boundary is controlled by the strength of AMOC. Only one of the models shows some evidence that AMOC variability at 45°N leads variability in the overturning freshwater transport at the southern boundary by about 30 years, but the other model shows no such coherence. In contrast, in both models this freshwater transport variability is dominated by local salinity variations. The third assumption is that changes in the overturning freshwater transport at the Atlantic southern boundary perturb the north-south density difference, and thus feed back on AMOC strength in the north. No evidence for this assumption is found in either model at any time scale, although thismore » does not rule out that the salt-advection feedback may be excited by a strong enough freshwater perturbation.« less

Authors:
ORCiD logo [1];  [2];  [3];  [3];  [3];  [3];  [1];  [4];  [2]
  1. Joint Institute for the Study of Atmosphere and Ocean, University of Washington, Seattle, Washington, Pacific Marine Environmental Laboratory, NOAA, Seattle, Washington
  2. Los Alamos National Laboratory, Los Alamos, New Mexico
  3. National Center for Atmospheric Research, Boulder, Colorado
  4. University of California, Berkeley, Berkeley, California
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER); National Oceanic and Atmospheric Administration (NOAA); National Science Foundation (NSF)
OSTI Identifier:
1460928
Alternate Identifier(s):
OSTI ID: 1477658; OSTI ID: 1561894
Report Number(s):
LA-UR-18-21355
Journal ID: ISSN 0894-8755
Grant/Contract Number:  
AC52-06NA25396; NA16OAR4310169; NA16OAR4310170; NA16OAR4310171; OCE-1243015; AC02-05CH11231
Resource Type:
Published Article
Journal Name:
Journal of Climate
Additional Journal Information:
Journal Name: Journal of Climate Journal Volume: 31 Journal Issue: 16; Journal ID: ISSN 0894-8755
Publisher:
American Meteorological Society
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Feedback; Meridional overturning circulation; Coupled models; Model output statistics; Numerical analysis/modeling; Oceanic variability

Citation Formats

Cheng, Wei, Weijer, Wilbert, Kim, Who M., Danabasoglu, Gokhan, Yeager, Steve G., Gent, Peter R., Zhang, Dongxiao, Chiang, John C. H., and Zhang, Jiaxu. Can the Salt-Advection Feedback Be Detected in Internal Variability of the Atlantic Meridional Overturning Circulation?. United States: N. p., 2018. Web. doi:10.1175/JCLI-D-17-0825.1.
Cheng, Wei, Weijer, Wilbert, Kim, Who M., Danabasoglu, Gokhan, Yeager, Steve G., Gent, Peter R., Zhang, Dongxiao, Chiang, John C. H., & Zhang, Jiaxu. Can the Salt-Advection Feedback Be Detected in Internal Variability of the Atlantic Meridional Overturning Circulation?. United States. doi:https://doi.org/10.1175/JCLI-D-17-0825.1
Cheng, Wei, Weijer, Wilbert, Kim, Who M., Danabasoglu, Gokhan, Yeager, Steve G., Gent, Peter R., Zhang, Dongxiao, Chiang, John C. H., and Zhang, Jiaxu. Wed . "Can the Salt-Advection Feedback Be Detected in Internal Variability of the Atlantic Meridional Overturning Circulation?". United States. doi:https://doi.org/10.1175/JCLI-D-17-0825.1.
@article{osti_1460928,
title = {Can the Salt-Advection Feedback Be Detected in Internal Variability of the Atlantic Meridional Overturning Circulation?},
author = {Cheng, Wei and Weijer, Wilbert and Kim, Who M. and Danabasoglu, Gokhan and Yeager, Steve G. and Gent, Peter R. and Zhang, Dongxiao and Chiang, John C. H. and Zhang, Jiaxu},
abstractNote = {Evidence for the assumptions of the salt-advection feedback in box models is sought by studying the Atlantic meridional overturning circulation (AMOC) internal variability in the long preindustrial control runs of two Earth system models. The first assumption is that AMOC strength is proportional to the meridional density difference between the North Atlantic and the Southern Oceans. The model simulations support this assumption, with the caveat that nearly all the long time-scale variability occurs in the North Atlantic density. The second assumption is that the freshwater transport variability by the overturning at the Atlantic southern boundary is controlled by the strength of AMOC. Only one of the models shows some evidence that AMOC variability at 45°N leads variability in the overturning freshwater transport at the southern boundary by about 30 years, but the other model shows no such coherence. In contrast, in both models this freshwater transport variability is dominated by local salinity variations. The third assumption is that changes in the overturning freshwater transport at the Atlantic southern boundary perturb the north-south density difference, and thus feed back on AMOC strength in the north. No evidence for this assumption is found in either model at any time scale, although this does not rule out that the salt-advection feedback may be excited by a strong enough freshwater perturbation.},
doi = {10.1175/JCLI-D-17-0825.1},
journal = {Journal of Climate},
number = 16,
volume = 31,
place = {United States},
year = {2018},
month = {8}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: https://doi.org/10.1175/JCLI-D-17-0825.1

Figures / Tables:

FIG. 1 FIG. 1: Long-term mean Atlantic Ocean zonally integrated baroclinic meridional velocity [Sv (1 Sv [ 106m3 s-1)] in (a) ESM2M and (d) CESM1. Zonally averaged salinity minus 35 (psu) in (b) ESM2M and (e) CESM1. Freshwater transport by AMOC at each latitude, Fov(y) (Sv), in (c) ESM2M and (f) CESM1.more » The CESM1 result is redrawn in (c) (red line). No meridional smoothing is applied.« less

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Works referencing / citing this record:

Observable, low-order dynamical controls on thresholds of the Atlantic meridional overturning circulation
journal, September 2019


Stability of the Atlantic Meridional Overturning Circulation: A Review and Synthesis
journal, August 2019

  • Weijer, W.; Cheng, W.; Drijfhout, S. S.
  • Journal of Geophysical Research: Oceans, Vol. 124, Issue 8
  • DOI: 10.1029/2019jc015083

The Stability of the AMOC During Heinrich Events Is Not Dependent on the AMOC Strength in an Intermediate Complexity Earth System Model Ensemble
journal, August 2019

  • Goes, Marlos; Murphy, Lisa N.; Clement, Amy C.
  • Paleoceanography and Paleoclimatology, Vol. 34, Issue 8
  • DOI: 10.1029/2019pa003580