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:

Cheng, Wei  ^[1];

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Weijer, Wilbert ^[2]; Kim, Who M. ^[3]; Danabasoglu, Gokhan ^[3]; Yeager, Steve G. ^[3]; Gent, Peter R. ^[3]; Zhang, Dongxiao ^[1]; Chiang, John C. H. ^[4]; Zhang, Jiaxu ^[2]

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+ Show Author Affiliations

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:

Wed Aug 01 00:00:00 EDT 2018

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Lawrence Berkeley National Laboratory (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