Assessing reconstruction techniques of the Atlantic Ocean circulation variability during the last millennium

Moreno-Chamarro, Eduardo; Ortega, Pablo; González-Rouco, J. Fidel; Montoya, Marisa

doi:10.1007/s00382-016-3111-x

Cited by 14 publications

(17 citation statements)

References 71 publications

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“…While past changes in the gyre circulation are uncertain, these results corroborate earlier hypotheses based on proxy indicators that the deep branch of the Atlantic meridional overturning circulation weakened continuously during the twentieth century [23][24][25][26][27] . These findings also support model simulations showing that changes in the deep return flow of the overturning circulation are nearly balanced by comparable changes in the surface western boundary current on multidecadal and longer timescales [28][29][30][31][32] . Future studies should build on this foundation.…”

Section: Discussionsupporting

confidence: 85%

Likely weakening of the Florida Current during the past century revealed by sea-level observations

Piecuch

2020

Nat Commun

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The Florida Current marks the beginning of the Gulf Stream at Florida Straits, and plays an important role in climate. Nearly continuous measurements of Florida Current transport are available at 27°N since 1982. These data are too short for assessing possible multidecadal or centennial trends. Here I reconstruct Florida Current transport during 1909-2018 using probabilistic methods and principles of ocean physics applied to the available transport data and longer coastal sea-level records. Florida Current transport likely declined steadily during the past century. Transport since 1982 has likely been weaker on average than during 1909-1981. The weakest decadal-mean transport in the last 110 y likely took place in the past two decades. Results corroborate hypotheses that the deep branch of the overturning circulation declined over the recent past, and support relationships observed in climate models between the overturning and surface western boundary current transports at multidecadal and longer timescales.

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Section: Discussionsupporting

confidence: 85%

Likely weakening of the Florida Current during the past century revealed by sea-level observations

Piecuch

2020

Nat Commun

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“…Oxygen isotope ratios in foraminifera reflect both the temperature of calcification and the oxygen isotopic composition of water, which is related to salinity in the upper ocean. This allows for the reconstruction of seawater density, which has been used to infer the strength of the large-scale overturning (Lynch-Stieglitz et al 2006) and the strength of boundary currents (Lynch-Stieglitz et al 1999aMoreno-Chamarro et al 2016). The mean flow in the ocean is largely geostrophic and thus is reflected in the mean density structure.…”

Section: Proxies Relevant To Reconstruction Of the Atlantic Meridionamentioning

confidence: 99%

The Atlantic Meridional Overturning Circulation and Abrupt Climate Change

Lynch‐Stieglitz

2017

Annu. Rev. Mar. Sci.

236

140

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Abrupt changes in climate have occurred in many locations around the globe over the last glacial cycle, with pronounced temperature swings on timescales of decades or less in the North Atlantic. The global pattern of these changes suggests that they reflect variability in the Atlantic meridional overturning circulation (AMOC). This review examines the evidence from ocean sediments for ocean circulation change over these abrupt events. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich events is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger events, there is recent evidence supporting AMOC changes over most of these oscillations as well. The lack of direct evidence for circulation changes over the shortest events leaves open the possibility of other driving mechanisms for millennial-scale climate variability.

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“…(b) Mean Atlantic overturning streamfunction from 6 to 0 ka (unit: Sv). variability during the last millennium represents the AMOC variability quite well on the multidecadal time scale (Moreno-Chamarro et al, 2017). However, the RAPID observation, which consists of the Florida Current transport by cable, the Ekman transport by satellite observation, and the mid-ocean transport by an array of moored instruments, suggests a very weak correlation between the Florida Current and the AMOC on the subannual time scale (Cunningham et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Time Scale Dependence of the Meridional Coherence of the Atlantic Meridional Overturning Circulation

Liu

2020

JGR Oceans

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The Atlantic Meridional Overturning Circulation (AMOC) variability is suggested to be incoherent between the subpolar and subtropical gyres in the Atlantic on interannual and even decadal time scales, questioning the representativeness of AMOC variability at a single latitude in modern observation and paleoreconstruction. Paleoreconstructions of the Florida Current transport suggest that Florida Current variability is associated with the AMOC on the millennial time scale, but the Rapid Climate Change (RAPID) mooring array suggests a weak correlation between the Florida Current and the AMOC. In this study, we investigate the meridional coherence of AMOC variability and the relationship between the Florida Current variability and the AMOC variability on different time scales in a transient 20,000‐year simulation. We find that with the increase of time scales, the meridional coherence of the AMOC increases. On decadal and longer time scales, the coherent subtropical and subpolar AMOC is caused by the coherent buoyancy forcing in the subpolar gyre. Also, the Florida Current transport is highly correlated with AMOC variability on decadal and longer time scales, suggesting that observations of the Florida Current can be used to indicate AMOC variability on long time scales.

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Assessing reconstruction techniques of the Atlantic Ocean circulation variability during the last millennium

Cited by 14 publications

References 71 publications

Likely weakening of the Florida Current during the past century revealed by sea-level observations

Likely weakening of the Florida Current during the past century revealed by sea-level observations

The Atlantic Meridional Overturning Circulation and Abrupt Climate Change

Time Scale Dependence of the Meridional Coherence of the Atlantic Meridional Overturning Circulation

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