Improved simulation of ENSO variability through feedback from the equatorial Atlantic in a pacemaker experiment

Abstract. To better characterize the climate variability of the last millennium in the high Andes, we analysed the pollen content of a 1100-yr-old sediment core collected in a bog located at 3800 m a.s.l. in the páramo in the Eastern Cordillera in Ecuador. An upslope convective index based on the ratio between cloud transported pollen from the andean forest to the bog (T) and Poaceae pollen frequencies, related to the edaphic moisture of the páramo (P), was defined to distinguish the atmospheric moisture from the soil moisture content of the páramo. Results showed that between 900 AD and 1230 AD, the Medieval Climate Anomaly interval was warm and moist with high T/P index linked to a high ENSO variability and a weak South American Summer Monsoon (SASM) activity. Between 1230 and 1650 AD, a dry climate prevailed characterized by an abrupt decrease in the T/P index related to lower ENSO variability with significant impact on the floristic composition of the páramo. During the Little Ice Age, two phases were observed, first a wet phase between 1650 and 1750 AD linked to low ENSO variability in the Pacific and warm south equatorial Atlantic SSTs favored the return of a wet páramo, and a cold and dry phase between 1750 and 1810 AD associated with low ENSO variability and weak SASM activity resulting in drying of the páramo. The Current Warm Period marks the beginning of a climate characterized by high convective activity, the highest in the last millennium, and weaker SASM activity modifying the water stock of the páramo. Our results show that the páramo is progressively loosing its capacity for water storage and that the variability of both tropical Pacific and Atlantic SSTs matters for Andean climate patterns although many teleconnection mechanisms are still poorly understood.

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Study of the Contourite Drift north of the Kane Gap (eastern equatorial Atlantic)

Russian Journal of Earth Sciences ◽

10.2205/2019es000658 ◽

2019 ◽

Vol 19 (2) ◽

pp. 1-9

Author(s):

V. V. Sivkov ◽

L. D. Bashirova ◽

E. V. Dorokhova ◽

M. V. Kapustina ◽

E. P. Ponomarenko

Keyword(s):

Equatorial Atlantic

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Crustal Heat Flow Variations of in the Equatorial Atlantic: Implications for geothermal structure of NE Brazil

10.22564/2simbgf2006.006 ◽

2006 ◽

Author(s):

Roberto R. Cardoso ◽

Valiya M. Hamza

Keyword(s):

Heat Flow ◽

Equatorial Atlantic ◽

Heat Flow Variations

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Vertical Structure of the Seasonal Cycle in the Central Equatorial Atlantic Ocean: XBT Sections from 1980 to 1988

Journal of Physical Oceanography ◽

10.1175/1520-0485(1991)021<0277:vsotsc>2.0.co;2 ◽

1991 ◽

Vol 21 (2) ◽

pp. 277-291 ◽

Cited By ~ 15

Author(s):

G. Reverdin ◽

P. Rual ◽

Y. Du Penhoat ◽

Y. Gouriou

Keyword(s):

Atlantic Ocean ◽

Seasonal Cycle ◽

Vertical Structure ◽

Equatorial Atlantic ◽

Equatorial Atlantic Ocean

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Diabatic heating governs the seasonality of the Atlantic Niño

Nature Communications ◽

10.1038/s41467-020-20452-1 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Hyacinth C. Nnamchi ◽

Mojib Latif ◽

Noel S. Keenlyside ◽

Joakim Kjellsson ◽

Ingo Richter

Keyword(s):

Feedback Loop ◽

Diabatic Heating ◽

Seasonal Migration ◽

Equatorial Atlantic ◽

Bjerknes Feedback ◽

Atlantic Sector ◽

Inter Tropical Convergence Zone ◽

Sst Variability ◽

Leading Mode ◽

Atlantic Niño

AbstractThe Atlantic Niño is the leading mode of interannual sea-surface temperature (SST) variability in the equatorial Atlantic and assumed to be largely governed by coupled ocean-atmosphere dynamics described by the Bjerknes-feedback loop. However, the role of the atmospheric diabatic heating, which can be either an indicator of the atmosphere’s response to, or its influence on the SST, is poorly understood. Here, using satellite-era observations from 1982–2015, we show that diabatic heating variability associated with the seasonal migration of the Inter-Tropical Convergence Zone controls the seasonality of the Atlantic Niño. The variability in precipitation, a measure of vertically integrated diabatic heating, leads that in SST, whereas the atmospheric response to SST variability is relatively weak. Our findings imply that the oceanic impact on the atmosphere is smaller than previously thought, questioning the relevance of the classical Bjerknes-feedback loop for the Atlantic Niño and limiting climate predictability over the equatorial Atlantic sector.

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Atlantic Niño/Niña Prediction Skills in NMME Models

Atmosphere ◽

10.3390/atmos12070803 ◽

2021 ◽

Vol 12 (7) ◽

pp. 803

Author(s):

Ran Wang ◽

Lin Chen ◽

Tim Li ◽

Jing-Jia Luo

Keyword(s):

Sea Surface ◽

Prediction Skill ◽

Boreal Summer ◽

Boreal Winter ◽

Equatorial Atlantic ◽

Multimodel Ensemble ◽

Spring Predictability Barrier ◽

Anomaly Correlation Coefficient ◽

Earth’S Climate ◽

Atlantic Niño

The Atlantic Niño/Niña, one of the dominant interannual variability in the equatorial Atlantic, exerts prominent influence on the Earth’s climate, but its prediction skill shown previously was unsatisfactory and limited to two to three months. By diagnosing the recently released North American Multimodel Ensemble (NMME) models, we find that the Atlantic Niño/Niña prediction skills are improved, with the multi-model ensemble (MME) reaching five months. The prediction skills are season-dependent. Specifically, they show a marked dip in boreal spring, suggesting that the Atlantic Niño/Niña prediction suffers a “spring predictability barrier” like ENSO. The prediction skill is higher for Atlantic Niña than for Atlantic Niño, and better in the developing phase than in the decaying phase. The amplitude bias of the Atlantic Niño/Niña is primarily attributed to the amplitude bias in the annual cycle of the equatorial sea surface temperature (SST). The anomaly correlation coefficient scores of the Atlantic Niño/Niña, to a large extent, depend on the prediction skill of the Niño3.4 index in the preceding boreal winter, implying that the precedent ENSO may greatly affect the development of Atlantic Niño/Niña in the following boreal summer.

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