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

Here, 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. Finally, no evidence for this assumption is found in either model at any time scale,more » although this does not rule out that the salt-advection feedback may be excited by a strong enough freshwater perturbation.« less
Authors:
ORCiD logo [1] ; ORCiD logo [2] ;  [3] ;  [3] ;  [3] ;  [3] ;  [1] ;  [4] ; ORCiD logo [2]
  1. Univ. of Washington, Seattle, WA (United States); Pacific Marine Environmental Laboratory, NOAA, Seattle, WA (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. National Center for Atmospheric Research, Boulder, CO (United States)
  4. Univ. of California, Berkeley, CA (United States)
Publication Date:
Report Number(s):
LA-UR-18-21355
Journal ID: ISSN 0894-8755
Grant/Contract Number:
AC52-06NA25396
Type:
Published Article
Journal Name:
Journal of Climate
Additional Journal Information:
Journal Volume: 31; Journal Issue: 16; Journal ID: ISSN 0894-8755
Publisher:
American Meteorological Society
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC). Biological and Environmental Research (BER) (SC-23); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Feedback; Meridional overturning circulation; Coupled models; Model output statistics; Numerical analysis/modeling; Oceanic variability
OSTI Identifier:
1460928
Alternate Identifier(s):
OSTI ID: 1477658

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., 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: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. 2018. "Can the Salt-Advection Feedback Be Detected in Internal Variability of the Atlantic Meridional Overturning Circulation?". United States. doi: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 = {Here, 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. Finally, 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 = {7}
}