Predictability and Decadal Variability of the North Atlantic Ocean State Evaluated from a Realistic Ocean Model

Journal Article · Thu Dec 22 00:00:00 EST 2016 · Journal of Climate

DOI:https://doi.org/10.1175/jcli-d-16-0323.1· OSTI ID:1537014

Sévellec, Florian ^[1]; Fedorov, Alexey V. ^[2]

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1. Univ. of Southampton (United Kingdom); DOE/OSTI
2. Yale Univ., New Haven, CT (United States)

This study investigates the excitation of decadal variability and predictability of the ocean climate state in the North Atlantic. Specifically, initial linear optimal perturbations (LOPs) in temperature and salinity that vary with depth, longitude, and latitude are computed, and the maximum impact on the ocean of these perturbations is evaluated in a realistic ocean general circulation model. The computations of the LOPs involve a maximization procedure based on Lagrange multipliers in a nonautonomous context. To assess the impact of these perturbations four different measures of the North Atlantic Ocean state are used: meridional volume and heat transports (MVT and MHT) and spatially averaged sea surface temperature (SST) and ocean heat content (OHC). It is shown that these metrics are dramatically different with regard to predictability. Whereas OHC and SST can be efficiently modified only by basin-scale anomalies, MVT and MHT are also strongly affected by smaller-scale perturbations. This suggests that instantaneous or even annual-mean values of MVT and MHT are less predictable than SST and OHC. Only when averaged over several decades do the former two metrics have predictability comparable to the latter two, which highlights the need for long-term observations of the Atlantic meridional overturning circulation in order to accumulate climatically relevant data. This study also suggests that initial errors in ocean temperature of a few millikelvins, encompassing both the upper and deep ocean, can lead to ~0.1-K errors in the predictions of North Atlantic sea surface temperature on interannual time scales. This transient error growth peaks for SST and OHC after about 6 and 10 years, respectively, implying a potential predictability barrier.

• Research Organization: Yale Univ., New Haven, CT (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: SC0016538
• OSTI ID: 1537014
• Journal Information: Journal of Climate, Journal Name: Journal of Climate Journal Issue: 2 Vol. 30; ISSN 0894-8755
• Publisher: American Meteorological Society
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
Meteorology & Atmospheric Sciences