Weakened SST variability in the tropical Atlantic Ocean since 2000

Prigent, Arthur; Lübbecke, Joke F.; Bayr, Tobias; Latif, Mojib; Wengel, Christian

doi:10.1007/s00382-020-05138-0

Cited by 53 publications

(63 citation statements)

References 67 publications

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“…Atlantic diminished during the recent decades, as reported by Prigent et al (2020). Lower zonal wind stress variability tends to reduce EKW activity that is an important driver of SST in the ABA.…”

Section: 1029/2020gl089348mentioning

confidence: 63%

“…This lack of surface warming denotes an 11% amplification of the mean SST annual cycle in that region. Recently, Prigent et al (2020), using observations and reanalysis products, found that the equatorial Atlantic interannual SST variability in May-June-July has reduced by 31% during 2000-2017 relative to 1982-1999. Interannual SST variability in the equatorial Atlantic and Angola-Benguela area (ABA) are strongly connected Lübbecke et al, 2010;Reason et al, 2006). Hence, it may well be that the SST variability in the southeastern tropical Atlantic also has undergone a reduction since 2000, which is the topic of this study.…”

Section: Introductionmentioning

confidence: 99%

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Origin of Weakened Interannual Sea Surface Temperature Variability in the Southeastern Tropical Atlantic Ocean

Prigent

Koungue

Lübbecke

et al. 2020

Geophysical Research Letters

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Observations and reanalysis products are used to investigate the substantial weakening in the southeastern tropical Atlantic sea surface temperature (SST) variability since 2000. Relative to 1982-1999, the March-April-May SST variability in the Angola-Benguela area (ABA) has decreased by more than 30%. Both equatorial remote forcing and local forcing are known to play an important role in driving SST variability in the ABA. Compared to 1982-1999, since 2000, equatorial remote forcing had less influence on ABA SSTs, whereas local forcing has become more important. In particular, the robust correlation that existed between the equatorial zonal wind stress and the ABA SSTs has substantially weakened, suggesting less influence of Kelvin waves on ABA SSTs. Moreover, the strong correlation linking the South Atlantic Anticyclone and the ABA SSTs has reduced. Finally, multidecadal surface warming of the ABA could also have played a role in the weakening of the interannual SST variability. Plain Language Summary Every few years, the southeastern tropical Atlantic Ocean experiences anomalous sea temperatures that affect fisheries and rainfall. Using observations and reanalysis data, we quantify the Angola-Benguela area (ABA) sea surface temperature (SST) variability during the last decades. Relative to 1982-1999, the March-April-May SST variability in the ABA has decreased by more than 30% since 2000. Remote equatorial forcing through equatorially and coastally trapped oceanic waves and variations in the local winds are the main drivers of ABA SST variability. Since 2000, we find that ABA SSTs are less connected to equatorial winds and exhibit a weaker link with the South Atlantic Anticyclone. Finally, the surface warming of the ABA observed during the post-2000 period also could have played a role in the weakening interannual SST variability.

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Section: 1029/2020gl089348mentioning

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Origin of Weakened Interannual Sea Surface Temperature Variability in the Southeastern Tropical Atlantic Ocean

Prigent

Koungue

Lübbecke

et al. 2020

Geophysical Research Letters

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“…The interannual climate variability over the equatorial Atlantic has weakened during the recent decades (Tokinaga & Xie, 2011; Prigent et al, 2020). However, it remains unclear how the warming hole is related to changes in interannual variability, including fluctuations in the SST variance and spatial structure (Martín‐Rey et al, 2018, 2019).…”

Section: Discussionmentioning

confidence: 99%

A Satellite Era Warming Hole in the Equatorial Atlantic Ocean

et al. 2020

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Observations during the satellite era 1979-2018 only depict small sea surface temperature (SST) trends over the Equatorial Atlantic cold tongue region in boreal summer. This lack of surface warming of the cold tongue, termed warming hole here, denotes an 11% amplification of the mean SST annual cycle. The warming hole is driven by a shoaling of the equatorial thermocline, linked to increased wind stress forcing, and damped by the surface turbulent heat fluxes. The satellite era warming deficit is not unusual during the twentieth century-similar weak trends were also observed during the 1890s-1910s and 1940s-1960s. The tendency for surface cooling appears to reflect an interaction of external forcing, which controls the timing and magnitude of the cooling, with the intrinsic variability of the climate system. The hypothesis for externally forced modulation of internal variability is supported by climate model simulations forced by the observed time-varying concentrations of atmospheric greenhouse gases and natural aerosols. These show that increased greenhouse forcing warmed the cold tongue and aerosols cooled it during the satellite era. However, internal variability, as derived from control integrations with fixed, preindustrial values of greenhouse gases and aerosols, can potentially cause larger cooling than observed during the satellite era. Large uncertainties remain on the relative roles of external forcing and intrinsic variability in both observations and coupled climate models.Plain Language Summary The Atlantic cold tongue is a region of locally cooler ocean surface waters that develops just south of the equator in boreal summer, partly reflecting the upwelling of deep cold waters by the action of the southeasterly trade winds. Although there has been considerable global warming since the beginning of global satellite measurements in 1979, there is hardly any surface warming in the Atlantic cold tongue region during 1979-2018. This warming hole is most pronounced in boreal summer. Observations suggest that despite strong heat transfer from the atmosphere to the ocean, the upper ocean may have cooled. Climate model simulations show that variations in external forcing associated with greenhouse gases can cause warming of the cold tongue and aerosols cooling of it. However, model simulations that exclude variations in these external forcing show that the mechanisms internal to the climate system can potentially cause larger cooling than observed during the satellite era. Thus, we attribute the warming hole to a combination of internal variability and external forcing. It must be stressed, however, that understanding the relative roles of internal variability versus external forcing is greatly hampered by large errors in both the observational data sets and climate models.

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“…The only substantial difference between the results presented here and the previous results was that the eastern Atlantic was significantly more active (at the 99% confidence level) even when considering the small sample size. This may be due to increased SSTs over this part of the Atlantic during the last decade (e.g., [40]). A comparison of the length of the TC season (not shown here) to previous results [1] would demonstrate that the Atlantic Region TC season may be beginning about 2 weeks earlier than June 1 as TCs were observed in May for 5 of the 10 years during this decade.…”

Section: Interannual and Interdecadal Variabilitymentioning

confidence: 99%

The Interannual and Interdecadal Variability in Tropical Cyclone Activity: A Decade of Changes in the Climatological Character

Lupo¹,

Heaven²,

Matzen³

et al. 2020

Current Topics in Tropical Cyclone Research

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During the last decade, there has been concern that the frequency or intensity of tropical cyclones (TCs) has increased. Also, climate models have shown varying results regarding the future occurrence and intensities of TC. Previous research from this group showed there is significant interannual and interdecadal variability in TC occurrence and intensity for some tropical ocean basins and sub-basins. This work examines global TC occurrence and intensity from 2010 to 2019 and compares this period to the same quantities from 1980 to 2009. The data used here are obtained from publicly available TC archives. Globally, the number of TC occurring over the latest decade is similar to the previous decade. However, while the 40-year trend shows an increase in TC, only intense hurricanes have shown an increase. The Atlantic Ocean and North Indian Ocean Basins show increases in TC activity, especially intense storms. The Southern Hemisphere and West Pacific Region show decreases in TC activity. In the West Pacific, intense TC did not increase, but the fraction of storms classified as intense increased. Only East Pacific TC activity showed no significant short- or long-term trends. Interannual and interdecadal variability in each sub-basin was found and there were some differences with previous work.

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Weakened SST variability in the tropical Atlantic Ocean since 2000

Cited by 53 publications

References 67 publications

Origin of Weakened Interannual Sea Surface Temperature Variability in the Southeastern Tropical Atlantic Ocean

Origin of Weakened Interannual Sea Surface Temperature Variability in the Southeastern Tropical Atlantic Ocean

A Satellite Era Warming Hole in the Equatorial Atlantic Ocean

The Interannual and Interdecadal Variability in Tropical Cyclone Activity: A Decade of Changes in the Climatological Character

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