Effect of Atlantic Meridional Overturning Circulation Changes on Tropical Atlantic Sea Surface Temperature Variability: A 2½-Layer Reduced-Gravity Ocean Model Study

Wen, Caihong; Chang, Ping; Saravanan, R.

doi:10.1175/2009jcli3042.1

Cited by 15 publications

(5 citation statements)

References 43 publications

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“…For example, Zhang et al (2011) show an apparent correlation between the NBC transport time series and the formation of Labrador Sea Water. Further support for this connection comes from model studies, where significant correlations exist between the AMOC strength and the NBC transport (Wen et al, 2010;Rühs et al, 2015). Rühs et al (2015) show that buoyancy-induced changes in the AMOC manifest themselves in the NBC, but that the variations are masked by strong interannual to decadal wind-driven gyre variability of the NBC.…”

Section: Introductionmentioning

confidence: 98%

Southern Ocean Origin of Multidecadal Variability in the North Brazil Current

Westen

Dijkstra

2017

Geophysical Research Letters

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Analysis of model data from a long (200 years) simulation of a high‐resolution version of the Parallel Ocean Program indicates a connection between a mode of multidecadal variability in the Southern Ocean, the so‐called Southern Ocean Mode, and multidecadal variability in the North Brazil Current. The multidecadal sea surface height variability in the Southern Ocean propagates northward and submerges at about 40°S. Northward propagating anomalies in ocean heat content are found between 5° and 40°S at depths down to 1 km and affect the North Brazil Current. Similar variability and connections between Southern Ocean and North Brazil Current are also found in a (200 years) simulation of a high‐resolution global version of the Community Earth System Model. The results provide a new mechanism for the low‐frequency variability of the North Brazil Current.

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Section: Introductionmentioning

confidence: 98%

Southern Ocean Origin of Multidecadal Variability in the North Brazil Current

Westen

Dijkstra

2017

Geophysical Research Letters

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“…Simulation of a disruption of the AMOC by imposing massive fresh water over the North Atlantic, experiment referred to as "water hosing", produces a negative AMO-like signal. The adjustment of the system to the equilibrium state occurs, at least, in two states: a fast atmospheric adjustment from the North Atlantic SST anomalies, which includes a change in the North Pacific via anomalous westerly winds (Dong and Sutton, 2002a;Wu et al, 2008;Chiang et al, 2008) and a slow oceanic adjustment, which seems to be the responsible for the major warming over the equatorial and South Tropical Atlantic (Chang et al, 2008;Wu et al, 2008;Wen et al, 2010) tightly related to the anomalous northward return flow over the western boundary (reverse of the North Brazil Current, NBC) which permits the penetration of the subsurface warming over the north tropical Atlantic into the equatorial thermocline (Jochum and Malanotte-Rizzoli, 2001;Hazeleger and Drijfhout, 2006;Chang et al, 2008;Wen et al, 2010). Besides, similar to the SST anomalies over the extratropics, the dipolar SST over the Atlantic is explained in part by Wind-Evaporation-SST feedback (WES; Chang et al, 1997), intensifying the anomalous northeasterly winds and its thermodynamic interaction within the oceanic mixed layer (Chiang et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Changes in tropical Atlantic interannual variability from a substantial weakening of the meridional overturning circulation

2013

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In response to a substantial weakening of the Atlantic Meridional Overturning Circulation (AMOC)-from a coupled ocean-atmosphere general circulation model experiment-significant changes in the interannual variability are found over the tropical Atlantic, characterized by an increase of variance (by ~150%) in boreal late spring-early summer and a decrease of variance (by ~60%) in boreal autumn. This study focuses on understanding physical mechanisms responsible for these changes in interannual variability in the tropical Atlantic. It demonstrates that the increase of variability in spring is a consequence of an increase in the variance of the El Niño-Southern Oscillation, which has a large impact on the tropical Atlantic via anomalous surface heat fluxes. Winter El Niño (La Niña) affects the eastern equatorial Atlantic by decreasing (increasing) cloud cover and surface wind speed which is associated with anomalous downward (upward) short wave radiation and reduced (enhanced) upward latent heat fluxes, creating anomalous positive (negative) Sea Surface Temperature (SST) anomalies over the region from winter to spring. On the other hand, the decrease of SST variance in autumn is due to a deeper mean thermocline which weakens the impact of the thermocline movement on SST variation. The comparison between the model results and observations is not straightforward owing to the influence of model biases and the lack of a major MOC weakening event in the instrumental record. However, it is argued that the basic physical mechanisms found in the model simulations are likely to be robust and therefore have relevance to understanding tropical Atlantic variability in the real world, perhaps with modified seasonality.

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“…Despite the proximity of core locations, some proxy reconstructions record a surface cooling, while others indicate a warming. Our studies (Wan et al, 2009) (Wen et al, 2010a). We found that the North Brazil Current (NBC) reverses its direction in response to a shutdown of the AMOC.…”

Section: A) Hierarchical Modeling Of Past Climate Changementioning

confidence: 73%

Final Report on Hierarchical Coupled Modeling and Prediction of Regional Climate Change in the Atlantic Sector

Saravanan

2011

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We used an ocean-atmosphere general circulation model to examine the link between oceanographic changes in the North Atlantic Ocean and changes in the strength of the African monsoon (Chang et al., 2008). Our simulations show that when North Atlantic thermohaline circulation is substantially weakened, the flow of the subsurface North Brazil Current reverses. This leads to decreased upper tropical ocean stratification and warmer sea surface temperatures in the equatorial South Atlantic Ocean, and consequently reduces African summer monsoonal winds and rainfall over West Africa. This mechanism is in agreement with reconstructions of past climate. Our results suggest that the interaction between thermohaline circulation in the North Atlantic Ocean and wind-driven currents in the tropical Atlantic Ocean contributes to the rapidity of African monsoon transitions during abrupt climate change events.A conundrum exists regarding whether the sea-surface temperatures (SST) decreased or increased over the southern Caribbean and the western Tropical Atlantic region during the Younger Dryas when the North Atlantic cooled substantially and the Atlantic thermohaline circulation was weakened significantly. Despite the proximity of core locations, some proxy reconstructions record a surface cooling, while others indicate a warming. Our studies (Wan et al., 2009) using an intermediate coupled ocean-atmosphere

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Effect of Atlantic Meridional Overturning Circulation Changes on Tropical Atlantic Sea Surface Temperature Variability: A 2½-Layer Reduced-Gravity Ocean Model Study

Cited by 15 publications

References 43 publications

Southern Ocean Origin of Multidecadal Variability in the North Brazil Current

Southern Ocean Origin of Multidecadal Variability in the North Brazil Current

Changes in tropical Atlantic interannual variability from a substantial weakening of the meridional overturning circulation

Final Report on Hierarchical Coupled Modeling and Prediction of Regional Climate Change in the Atlantic Sector

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