A dynamically based method for estimating the Atlantic meridional overturning circulation at 26° N from satellite altimetry

Sanchez-Franks, Alejandra; Frajka‐Williams, Eleanor; Moat, Ben; Smeed, David A.

doi:10.5194/os-17-1321-2021

Cited by 6 publications

(17 citation statements)

References 68 publications

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“…At interannual time scales, the present AMOC skill is similar to the maximal skill achieved by the dynamically‐based method of Sanchez‐Franks et al. (2021), but here the skill additionally remains high over a wide range of time scales. The method of Frajka‐Williams (2015) achieved even higher skill based on linear regression of altimetric SSH (also using wind stress and the in situ observed Florida Strait velocity), but did not separate the data into training and testing partitions.…”

Section: Evaluating the Methodology: Reconstructing Moc At Select Lat...supporting

confidence: 77%

“…The SSH to basin-interior AMOC relation was derived via linear regression. Sanchez-Franks et al (2021) have derived the basin-interior AMOC component via geostrophy from satellite SSH, wind stress data, and from the observed climatological stratification structure. Their AMOC reconstructions explained ≈70% of RAPID-MOCHA array AMOC variability at inter-annual timescales.…”

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confidence: 99%

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Machine Learning‐Derived Inference of the Meridional Overturning Circulation From Satellite‐Observable Variables in an Ocean State Estimate

Solodoch

Stewart

Hogg

et al. 2023

J Adv Model Earth Syst

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The Meridional Overturning Circulation (MOC) is a critical component of the climate system, playing key roles in heat and material transport, deep ocean ventilation, and global water mass distribution and stratification (Talley, 2013). MOC deep waters form in several regions of the subpolar North Atlantic and of the Antarctic margins, from which they are exported globally in complicated patterns, carrying to their destinations the signatures of their air-sea interactions prior to ventilation. Monitoring and deducing the global MOC transport is thus crucial for understanding of ocean circulation and climate variability. Traditionally, the MOC was estimated using geostrophy and inverse methods from ship-based hydrographic measurements (Wunsch, 1996). However, the sparseness of ship hydrography in time and space limits the recoverable information, and can lead to severe aliasing, for example, of temporal variability (Frajka-Williams et al., 2019). In the last two decades, dedicated in situ monitoring arrays have been put in place at several latitudes, although only in the Atlantic Ocean. Several arrays span the width of the basin: the RAPID-MOCHA array at 26. 5°N (Cunningham et al., 2007;

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Section: Evaluating the Methodology: Reconstructing Moc At Select Lat...supporting

confidence: 77%

mentioning

confidence: 99%

Machine Learning‐Derived Inference of the Meridional Overturning Circulation From Satellite‐Observable Variables in an Ocean State Estimate

Solodoch

Stewart

Hogg

et al. 2023

J Adv Model Earth Syst

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“…At 26.5° N, an additional reconstruction has extended the AMOC timeseries using Gulf Stream cable measurements and sea-level anomalies measured by satellite altimetry 101 , with an updated reconstruction taking into account the vertical structure 102 . Building on a clear relationship between western boundary sea-level anomalies and upper mid-ocean geostrophic transport changes, these reconstructions recover a large fraction of the directly observed AMOC interannual variability 101 .…”

Section: Southward Communication Of Amoc Anomaliesmentioning

confidence: 99%

“…(panel e). Reconstructed AMOC in the subtropical North Atlantic (right): AMOC at 26.5° N from the RAPID array98 (panel f); AMOC from observations at 26.5° N (ref 102. ) (panel g);…”

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confidence: 99%

The evolution of the North Atlantic Meridional Overturning Circulation since 1980

Jackson

Biastoch

Buckley

et al. 2022

Nat Rev Earth Environ

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The Atlantic Meridional Overturning Circulation (AMOC) (Box 1) is a system of ocean currents in the Atlantic that move warmer, upper waters northwards and cooler, deeper waters southwards. Accordingly, the AMOC is a major source of northward heat transport, accounting for 20-30% of total atmospheric and oceanic heat transport into the mid-latitudes 1 . The AMOC, therefore, has a key role in governing the climate of the North Atlantic region and beyond, influencing European air temperatures and precipitation, the frequency of Atlantic hurricanes and winter storms, spatial patterns of sea level and tropical monsoons 2,3 , and the global carbon budget 4 .The strength of the AMOC is typically 17 Sverdrups (Sv; 1 Sv = 10 6 m 3 s −1 ) 5 . However, both observations and models indicate that the AMOC exhibits substantial variability on daily to multi-decadal timescales. Coupled climate models suggest decadal variability can arise naturally due to internal interactions within the climate system [6][7][8] . The AMOC is also expected to respond to external forcing, including anthropogenic aerosols, volcanic eruptions and solar changes 9,10 , as well as anthropogenic greenhouse gas emissions 11 . Indeed, observations, reanalyses, models and proxies [12][13][14][15][16] indicate substantial contemporary decadal-scale changes in AMOC strength. The RAPID array at 26.5° N (refs 5,17 ), for example, revealed a statistically significant weakening from 2004 (refs 18,19 ), probably representing decadal variability rather than ongoing long-term weakening [20][21][22] . There are indications that the AMOC might be recovering in strength 12 .Despite evidence of decadal variability, many questions remain. For example, high-quality continuous observations, like the RAPID array, are short and sparse, making it difficult to assess longer-term AMOC variability and determine whether decadal changes are representative of those across the wider Atlantic. Moreover, there is uncertainty about the relative roles of internal variability and forced variability, owing to diverse AMOC variability 8,23 and externally forced AMOC trends 10,24 in models. Indeed, the AMOC might have already weakened over the twentieth century 25,26 , potentially implying that it is more sensitive to external forcing than previously thought. Understanding how and why the AMOC has changed on decadal timescales is thus crucial not only to understand the AMOC's role

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“…Sanchez‐Franks et al. (2021) extended the RAPID AMOC time series using satellite altimetry. Consistent with the NOAC AMOC, their time series exhibits an increase in 2000–2005, though their AMOC estimate shows no decline in the 1990s (Figure 2c).…”

Section: Resultsmentioning

confidence: 99%

Meridional Connectivity of a 25‐Year Observational AMOC Record at 47°N

Wett,

Rhein,

Kieke

et al. 2023

Geophysical Research Letters

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Since climate model studies project a decline of the Atlantic Meridional Overturning Circulation (AMOC) in the 21st century, monitoring AMOC changes remains essential. While AMOC variability is expected to be coherent across latitudes on longer than decadal timescales, connectivity on inter‐annual and seasonal timescales is less clear. Model studies and observational estimates disagree on the regions and timescales of meridional connectivity and AMOC observations at multiple latitudes are needed to study its connectivity. We calculate basin‐wide AMOC volume transports (1993–2018) from measurements of the North Atlantic Changes (NOAC) array at 47°N, combining data from moored instruments with hydrography and satellite altimetry. The mean NOAC AMOC is 17.2 Sv exhibiting no long‐term trend. Both the unfiltered and low‐pass filtered NOAC AMOC show a significant correlation with the RAPID‐MOCHA‐WBTS AMOC at 26°N when the NOAC AMOC leads by about one year.

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A dynamically based method for estimating the Atlantic meridional overturning circulation at 26° N from satellite altimetry

Cited by 6 publications

References 68 publications

Machine Learning‐Derived Inference of the Meridional Overturning Circulation From Satellite‐Observable Variables in an Ocean State Estimate

Machine Learning‐Derived Inference of the Meridional Overturning Circulation From Satellite‐Observable Variables in an Ocean State Estimate

The evolution of the North Atlantic Meridional Overturning Circulation since 1980

Meridional Connectivity of a 25‐Year Observational AMOC Record at 47°N

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