Control of the South Atlantic Convergence Zone by extratropical thermal forcing

Talento, Stefanie; Barreiro, Marcelo

doi:10.1007/s00382-017-3647-4

Cited by 12 publications

(11 citation statements)

References 30 publications

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“…It is also suggested that a hemispheric teleconnection exists between AMV and Antarctic sea-ice trends 45 . In the Southern Hemisphere, large-scale extratropical forcing has been shown to influence the strength of the South Atlantic Convergence Zone 46 .…”

Section: Basin-to-basin and Tropical-extratropical Teleconnectionsmentioning

confidence: 99%

Challenges and opportunities for improved understanding of regional climate dynamics

et al. 2018

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Dynamical processes in the atmosphere and ocean are central in determining the large-scale drivers of regional climate change, yet predictive understanding of climate dynamics is poor. In this perspective article, we identify three frontline problems in climate dynamics, in which progress is possible, and which will lead to improved predictions and projections and more robust information for climate change adaptation. These problems involve (i) the response to external forcing of storms, blocks and jet streams, (ii) ocean-basin to ocean-basin and tropical-extratropical teleconnections and (iii) the development of predictive theories of climate dynamics involving non-linear interactions between the dynamics and physics of the atmosphere and ocean. We highlight opportunities and techniques for making immediate progress in climate dynamics, namely the development of high-resolution coupled model simulations, partial coupling or pacemaker experiments and the development and use of dynamical metrics and dynamical hierarchies of models. Our particular focus is on the role of the ocean in providing a slowly-evolving boundary condition, and its coupling and interaction with the atmosphere, that plays a central role in driving internal climate variability and in modulating forced climate change.

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Section: Basin-to-basin and Tropical-extratropical Teleconnectionsmentioning

confidence: 99%

Challenges and opportunities for improved understanding of regional climate dynamics

et al. 2018

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“…In Table 1 we summarize the experiments. All the data are publicly available in Talento and Barreiro (2018).…”

Section: Experimental Designmentioning

confidence: 99%

“…If, in addition, the land surface temperature over Africa is maintained the ITCZ response completely vanishes, indicating that the ITCZ response to the extratropical forcing is not possible just through purely atmospheric processes, but rather it needs the involvement of either the tropical SST or the continental surface temperatures. With the same model configuration, Talento and Barreiro (2017) focus on the South Atlantic convergence zone (SACZ) and show that, during its peak in austral summer, its response to warming in the NH extratropics and cooling in the SH extratropics consists of weakening, mostly due to the NH component of the forcing. Both studies showed strong changes in the tropical band where SST, surface winds and precipitation are strongly coupled.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of the tropical climate to an interhemispheric thermal gradient: the role of tropical ocean dynamics

Talento

Barreiro

2018

Earth Syst. Dynam.

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Abstract. This study aims to determine the role of the tropical ocean dynamics in the response of the climate to extratropical thermal forcing. We analyse and compare the outcomes of coupling an atmospheric general circulation model (AGCM) with two ocean models of different complexity. In the first configuration the AGCM is coupled with a slab ocean model while in the second a reduced gravity ocean (RGO) model is additionally coupled in the tropical region. We find that the imposition of extratropical thermal forcing (warming in the Northern Hemisphere and cooling in the Southern Hemisphere with zero global mean) produces, in terms of annual means, a weaker response when the RGO is coupled, thus indicating that the tropical ocean dynamics oppose the incoming remote signal. On the other hand, while the slab ocean coupling does not produce significant changes to the equatorial Pacific sea surface temperature (SST) seasonal cycle, the RGO configuration generates strong warming in the central-eastern basin from April to August balanced by cooling during the rest of the year, strengthening the seasonal cycle in the eastern portion of the basin. We hypothesize that such changes are possible via the dynamical effect that zonal wind stress has on the thermocline depth. We also find that the imposed extratropical pattern affects El Niño–Southern Oscillation, weakening its amplitude and low-frequency behaviour.

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“…The mechanism proposed by Smith et al (2017) involves a warming of the North Atlantic Ocean leading to a reinforced atmospheric circulation. This is illustrated by Talento and Barreiro (2017) that have performed idealised numerical experiments in which a temperature increase of several degrees was prescribed at high latitudes to the model. In particular, they found a response consisting of a warming over the subtropical Atlantic Ocean, the Mediterranean Sea and 1 3 northern Africa, leading to a northward shift of the ITCZ and to an increase in Sahel precipitation.…”

Section: Introductionmentioning

confidence: 99%

Respective impacts of Arctic sea ice decline and increasing greenhouse gases concentration on Sahel precipitation

2018

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The impact of climate change on Sahel precipitation is uncertain and has to be widely documented. Recently, it has been shown that Arctic sea ice loss leverages the global warming effects worldwide, suggesting a potential impact of Arctic sea ice decline on tropical regions. However, defining the specific roles of increasing greenhouse gases (GHG) concentration and declining Arctic sea ice extent on Sahel climate is not straightforward since the former impacts the latter. We avoid this dependency by analysing idealized experiments performed with the CNRM-CM5 coupled model. Results show that the increase in GHG concentration explains most of the Sahel precipitation change. We found that the impact due to Arctic sea ice loss depends on the level of atmospheric GHG concentration. When the GHG concentration is relatively low (values representative of 1980s), then the impact is moderate over the Sahel. However, when the concentration in GHG is levelled up, then Arctic sea ice loss leads to increased Sahel precipitation. In this particular case the ocean-land meridional gradient of temperature strengthens, allowing a more intense monsoon circulation. We linked the non-linearity of Arctic sea ice decline impact with differences in temperature and sea level pressure changes over the North Atlantic Ocean. We argue that the impact of the Arctic sea ice loss will become more relevant with time, in the context of climate change.

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Control of the South Atlantic Convergence Zone by extratropical thermal forcing

Cited by 12 publications

References 30 publications

Challenges and opportunities for improved understanding of regional climate dynamics

Challenges and opportunities for improved understanding of regional climate dynamics

Sensitivity of the tropical climate to an interhemispheric thermal gradient: the role of tropical ocean dynamics

Respective impacts of Arctic sea ice decline and increasing greenhouse gases concentration on Sahel precipitation

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