Simultaneous Evolution of Gyre and Atlantic Meridional Overturning Circulation Anomalies as an Eigenmode of the North Atlantic System

Journal Article · 25 July 2017 · Journal of Climate

DOI: https://doi.org/10.1175/JCLI-D-16-0751.1 · OSTI ID:1544388

Zhao, Bowen ^[1]; Reichler, Thomas ^[1]; Strong, Courtenay ^[1]; Penland, Cecile ^[2]

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1. Univ. of Utah, Salt Lake City, UT (United States)
2. National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States). Earth System Research Lab.

Here, the authors observe an interdecadal oscillatory mode of the North Atlantic atmosphere–ocean system in a general circulation model (GFDL CM2.1) via a linear inverse model (LIM). The oscillation mechanism is mostly embedded in the subpolar gyre: anomalous advection generates density anomalies in the eastern subpolar gyre, which propagate along the mean gyre circulation and reach the subpolar gyre center around 10 years later, when associated anomalous advection of the opposite sign starts the other half cycle. While density anomalies reach the Labrador Sea deep convection region, Atlantic meridional overturning circulation (AMOC) anomalies are also induced. Both the gyre and AMOC anomalies then propagate equatorward slowly, following the advection of density anomalies. The oscillation is further demonstrated to be more likely an ocean-only mode while excited by the atmospheric forcing; in particular, it can be approximated as a linearly driven damped oscillator that is partly excited by the North Atlantic Oscillation (NAO). The slowly evolving interdecadal oscillation significantly improves and prolongs the LIM’s prediction skill of sea surface temperature (SST) evolution.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE; National Science Foundation (NSF)
• OSTI ID: 1544388
• Journal Information: Journal of Climate, Journal Name: Journal of Climate Journal Issue: 17 Vol. 30; ISSN 0894-8755
• Publisher: American Meteorological SocietyCopyright Statement
• Country of Publication: United States
• Language: English