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Cited by 321Climate variability and modelsOceanographic and Atmospheric ProcessesMeteorological Phenomena and Simulations

Understanding equatorial atlantic interannual variability

Open access
Keenlyside, Noel S., Latif, Mojib·2007·Journal of Climate
DOI 10.1175/jcli3992.1
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Abstract

An observational-based analysis of coupled variability in the equatorial Atlantic and its seasonality is presented. Regression analysis shows that the three elements of the Bjerknes positive feedback exist in the Atlantic and are spatially similar to those of the Pacific. The cross-correlation functions of the elements of the Bjerknes feedback are also similar and consistent with an ocean-atmosphere coupled mode. However, the growth rate in the Atlantic is up to 50% weaker, and explained variance is significantly lower. The Bjerknes feedback in the Atlantic is strong in boreal spring and summer, and weak in other seasons, which explains why the largest sea surface temperature anomalies (SSTAs) occur in boreal summer. Its seasonality is determined by seasonal variations in both atmospheric sensitivity to SSTA and SSTA sensitivity to subsurface temperature anomalies. © 2007 American Meteorological Society.

AI snapshot

Written from the paper’s full text.

TL;DR

This observational study finds that all three elements of the Bjerknes positive feedback exist in the equatorial Atlantic and resemble those in the Pacific, but the Atlantic feedback is weaker and explains less variance. The feedback is seasonally modulated, being strong in boreal spring and summer, which helps explain why equatorial Atlantic SST anomalies peak in boreal summer.

Key findings

  • All three Bjerknes feedback elements are present in the equatorial Atlantic with spatial structure and cross-correlation functions similar to the Pacific, consistent with an ocean–atmosphere coupled mode.
  • The Atlantic feedback is weaker: the growth rate is up to 50% weaker, and explained variance is significantly lower. For example, a 1°C SSTA corresponds to 0.55 m s⁻¹ averaged western Atlantic zonal wind versus 0.84 m s⁻¹ for Niño-4; a 10⁻² Pa westerly stress anomaly raises eastern Atlantic sea level by 2 cm versus 6 cm in the Pacific; and HC–SST coupling explains about 50% of variance in the Atlantic versus 80% in the Pacific.
  • The Bjerknes feedback in the Atlantic is strong in boreal spring and summer and weak in other seasons, explaining why the largest SSTAs occur in boreal summer.
  • Its seasonality is determined by seasonal variations in both atmospheric sensitivity to SSTA and SSTA sensitivity to subsurface temperature anomalies.

Methods

  • Observational analysis using COADS surface winds (1950–1997), NCEP–NCAR reanalysis surface stress (1950–2002), HadISST 1.1 SST, XBT-derived 400-m heat content (1970–2003), satellite sea level anomalies (1993–2002), and an NCEP-forced MPI-OM simulation (1950–2001).
  • Main analysis uses linearly detrended monthly anomalies, standard linear correlation and regression, cross-correlation functions to infer lags and feedback structure, and calendar-month regressions to estimate seasonality.
  • Significance is estimated with two-sided Student’s t tests, reducing degrees of freedom for serial correlation using decorrelation times.

Limitations

  • The paper states that the delayed negative ocean feedback is not addressed, though it is important for ENSO and predictability.
  • The paper notes data-quality concerns, especially for XBT/in situ subsurface data, and adopts a simple significance method because data quality is of more concern; it also notes uncertainty among datasets and that CGCMs poorly simulate the region’s climatology.
  • Evident from the text: the statistical analysis cannot determine causality or whether eastern SSTAs reinforce wind anomalies, and some key satellite-based results rely on the short 1993–2002 period.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1175/jcli3992.1

Cites

37 of 37 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

3 of 38 cited sources checked · 2 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    Western Atlantic zonal winds force heat content variations in the east.

    “Western Atlantic (WAtl) zonal winds clearly force HC variations in the east, but whether this forcing dominates the variability there is not clear.”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites Carton and Huang 1994

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Servain et al. 2000 source
    • cites Illig et al. 2004 source

      The Introduction (§1, paragraph 2; page not provided) reports a suggested link between relaxed western Atlantic trade winds and warm-water accumulation in the east. The Discussion (§6, paragraph 69; page not provided) finds that equatorial waves help the ocean adjust to wind forcing. These passages support a western-wind influence, but they do not establish as clearly as the claim states that western Atlantic zonal winds force eastern heat-content variations. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
  • Interpretationcitation

    The secondary peak in subsurface-surface coupling indicated by the satellite data is consistent with a secondary peak in upwelling in November-December.

    “The secondary peak indicated by the satellite data is consistent with a secondary peak in upwelling in November-December [as discussed by Okumura and Xie (2006)].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Okumura and Xie (2006) source
  • Findingown data

    The growth rate of the Bjerknes feedback in the Atlantic is up to 50% weaker than in the Pacific.

    “However, the growth rate in the Atlantic is up to 50% weaker, and explained variance is significantly lower.”
    Quote in the paperSubstantial claim
  • Findingown data

    The statistical analysis between wind stress and SST indicates that the delay is about a month less in the Atlantic than in the Pacific.

    “However, the statistical analysis between wind stress and SST indicates that the delay is about a month less in the Atlantic (Table 1), which would then mean that the growth rates in both basins were similar.”
    Quote in the paperSubstantial claim
  • Findingown data

    The sensitivity of the atmosphere to SSTAs over the Atlantic is weakest in the boreal autumn.

    “The sensitivity of the atmosphere to SSTAs over the Atlantic is weakest in the boreal autumn.”
    Quote in the paperNot a substantial claim
  • May combine two claims. 42
  • The quote only partly states this claim. 1
  • Classified as probably not a substantial claim. 2

  • May combine two claims.

    Findingcitation

    A semiannual component is evident in the relation between surface and subsurface in the Atlantic, particularly in satellite data, consistent with a secondary maximum in equatorial variability seen in satellite-derived SST.

    “A semiannual component is also evident in the relation, particularly in the satellite data, and is consistent with a secondary maximum in equatorial variability seen in satellite-derived SST (Okumura and Xie 2006).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Okumura and Xie 2006 source

  • May combine two claims.

    Findingown data

    The three elements of the Bjerknes positive feedback exist in the equatorial Atlantic and are spatially similar to those in the Pacific.

    “Regression analysis shows that the three elements of the Bjerknes positive feedback exist in the Atlantic and are spatially similar to those of the Pacific.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: ENSO is the result of a positive ocean-atmosphere feedback (the Bjerknes feedback) and a delayed negative ocean feedback.

  • The quote only partly states this claim.

    Findingown data

    The cross-correlation functions of the elements of the Bjerknes feedback in the Atlantic are similar to those in the Pacific.

    “The cross-correlation functions of the elements of the Bjerknes feedback are also similar and consistent with an ocean-atmosphere coupled mode.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Variability in the Atlantic peaks in boreal summer, and in the Pacific it peaks between November and January.

    “in the Atlantic variability peaks in boreal summer, and in the Pacific it peaks between November and January (Fig. 3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the Pacific, the seasonality in both COADS and NCEP-NCAR reanalysis are in good agreement, with atmosphere sensitivity to SSTA weakest during April to July.

    “In the Pacific, the seasonality in both COADS and NCEP-NCAR reanalysis are in good agreement, with atmosphere sensitivity to SSTA weakest during the period April to July.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In the Atlantic, the relationship explains a little more than 10% of the variability, whereas in the Pacific explained variances approach 20%.

    “In the Atlantic, this relationship explains a little more than 10% of the variability, whereas in the Pacific explained variances approach 20%.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The Bjerknes feedback in the Atlantic is strong in boreal spring and summer, and weak in other seasons.

    “The Bjerknes feedback in the Atlantic is strong in boreal spring and summer, and weak in other seasons, which explains why the largest sea surface temperature anomalies (SSTAs) occur in boreal summer.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingnone given

    In the Pacific, regression values between eastern Pacific SST and western Pacific zonal winds are of similar strength to those in the Atlantic, but correlation values are significantly higher.

    “In the Pacific, regression values are of similar strength to those in the Atlantic; correlation values are, however, significantly higher (not shown).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    A 1°C change in SST corresponds to maximum westerly wind anomaly of between 0.6-0.8 m s−1 in the Atlantic, or 0.55 m s−1 when averaged over the western Atlantic (3°S-3°N, 40°-20°W) region.

    “Regression values indicate that a 1°C change in SST corresponds to maximum westerly wind anomaly of between 0.6-0.8m s Ϫ1 (Fig. 1a), or 0.55 m s Ϫ1 when averaged over the western Atlantic (3°S-3°N, 40°-20°W) region (Table 1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In situ data suggest that regression values are weaker in the Atlantic than in the Pacific, but the quality of the in situ data is significantly poorer.

    “In contrast, the in situ data suggest that the regression values are weaker in the Atlantic, however, as discussed above the quality of the data is significantly poorer.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    An analysis of NCEP surface stress data produces essentially the same result, except explained variances are higher in both basins.

    “An analysis of NCEP surface stress data produces essentially the same result, except explained variances are higher in both basins (Table 1).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In the Atlantic, a 1°C SSTA would result in a 0.75 × 10−2 Pa westerly surface wind stress anomaly, which would in turn, with a 1 month delay, produce a 1.65-cm SLA, which would then result in about another month later an SSTA of 0.3°C.

    “In the Atlantic (Pacific), a 1°C SSTA would result in a 0.75 (0.74) ϫ 10 Ϫ2 Pa westerly surface wind stress anomaly, which would in turn, with a 1 month delay, produce a 1.65-cm (4.7-cm) SLA, which would then result in about another month later an SSTA of 0.3°C (0.6°C) (Table 1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the Pacific, a 1°C SSTA would result in a 0.74 × 10−2 Pa westerly surface wind stress anomaly, which would in turn, with a 1 month delay, produce a 4.7-cm SLA, which would then result in about another month later an SSTA of 0.6°C.

    “In the Atlantic (Pacific), a 1°C SSTA would result in a 0.75 (0.74) ϫ 10 Ϫ2 Pa westerly surface wind stress anomaly, which would in turn, with a 1 month delay, produce a 1.65-cm (4.7-cm) SLA, which would then result in about another month later an SSTA of 0.3°C (0.6°C) (Table 1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The strength of the coupling between eastern Atlantic SST and western Atlantic zonal winds (first element of the Bjerknes feedback) varies significantly over the year, with considerable uncertainty among different datasets.

    “The strength of the coupling between eastern Atlantic SST and western Atlantic zonal winds (first element of the Bjerknes feedback) varies significantly over the year, and quite a lot of uncertainty exists among different datasets (Fig. 4a).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the Pacific, regression values between surface and subsurface are weakest in the boreal spring, and strong through boreal summer to winter.

    “In contrast in the Pacific regression values are weakest in the boreal spring, and strong through boreal summer to winter.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingreasoning

    In the western tropical Pacific convection is present all year-round, whereas in the western Atlantic it is present from December to May and absent from August through October.

    “In the western tropical Pacific convection is present all year-round, whereas in the western Atlantic it is present from December to May (Fig. 4b) and absent from August through October.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the Pacific, the Bjerknes feedback is active all year-round, although it is weakest in boreal spring.

    “In the Pacific, our analysis indicates that the Bjerknes feedback is active all yearround, although it is weakest in boreal spring.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Explained variances in the boreal spring to summer months are around 0.65 in satellite-derived SLA data and 0.5 in OGCM HC data.

    “Explained variances in these months are around 0.65 (0.5) in the satellite-derived SLA (OGCM HC) data.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    All three elements of the Bjerknes feedback are present in the equatorial Atlantic and have similar spatial structure and cross-correlation functions as in the Pacific.

    “Analysis of the three elements of the Bjerknes feedback in both the Atlantic and the Pacific showed that all three elements are present in the equatorial Atlantic and have similar spatial structure and cross-correlation functions as in the Pacific.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The variance explained by these interactions is significantly less in the Atlantic than in the Pacific, indicating that other interactions also contribute significantly there.

    “Furthermore, the variance explained by these interactions is significantly less in the Atlantic than in the Pacific, indicating that other interactions also contribute significantly there.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The strength of the Bjerknes feedback has a strong seasonal cycle in the Atlantic, and is most effective during boreal spring and summer.

    “The strength of the Bjerknes feedback has a strong seasonal cycle in the Atlantic, and is most affective during boreal spring and summer.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Assuming a 2-month delay around the coupled loop, the growth rate in the Pacific is almost twice as strong as in the Atlantic.

    “Assuming that the delay around the coupled loop is indeed 2 months, then the growth rate in the Pacific is almost twice as strong as in the Atlantic.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: The delay around the coupled loop is 2 months.

  • May combine two claims.

    Premisecitation

    The equatorial Atlantic mode is associated with significant impacts over land, which are potentially predictable.

    “Nonetheless, this type of variability is associated with significant impacts over land (Hirst and Hastenrath 1983;Wagner and da Silva 1994;Carton and Huang 1994), which are potentially predictable (Goddard and Mason 2002), and is thus of practical importance.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Hirst and Hastenrath 1983

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Wagner and da Silva 1994 source
    • cites Carton and Huang 1994

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Premisecitation

    The Zebiak (1993) intermediate complexity model of the Atlantic simulates a coupled mode with a period of 4 yr, with similar physics to ENSO but strongly damped and only sustained by external forcing.

    “The Zebiak (1993) intermediate complexity model (ICM) of the Atlantic simulates a coupled mode with a period of 4 yr.”
    • Also stated in: § 1. Introduction · plain
      “The mode has similar physics to ENSO, but owing to the different background state, it is strongly damped and only sustained by external forcing.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Zebiak 1993 source
    • Rests on an assumption: ENSO is the result of a positive ocean-atmosphere feedback (the Bjerknes feedback) and a delayed negative ocean feedback.

  • May combine two claims.

    Premisereasoning

    In the Tropics, sea level variations are closely related to thermocline perturbations, and thus these data are a good proxy for both thermocline depth and upper-ocean HC variations.

    “In the Tropics, where the ocean can be approximated by a 1.5-layer system, sea level variations are closely related to thermocline perturbations, and thus these data are a good proxy for both thermocline depth and upper-ocean HC variations.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    The data extend back to 1955, but their quality becomes noticeably poorer before 1970.

    “The data extend back to 1955, but their quality becomes noticeably poorer before 1970.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Tourre and White (1995)

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Interpretationreasoning

    It is most probable that the growth rate is stronger in the Pacific than in the Atlantic, but not twice as strong.

    “Given that the largest difference in this calculation is mainly in the forcing of HC anomalies by wind stress anomalies, it is most probable that the growth rate is indeed stronger in the Pacific than in the Atlantic, but not twice as strong.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Spectral analysis shows that the equatorial Atlantic variability is only weakly oscillatory (2yr period) and otherwise similar to a red noise process.

    “However, spectral analysis shows that the variability is only weakly oscillatory (2yr period) and otherwise similar to a red noise process (Latif and Grötzner 2000;Ruiz-Barradas et al. 2000).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Latif and Grötzner 2000 source
    • cites Ruiz-Barradas et al. 2000 source

  • May combine two claims.

    Premisecitation

    AGCMs forced by observed SST show that the atmosphere is sensitive to eastern Atlantic SSTA, although the sensitivity varies seasonally and is model dependent.

    “Results from atmosphere general circulation models (AGCMs) forced by observed SST also show that the atmosphere is indeed sensitive to eastern Atlantic SSTA, although the sensitivity varies seasonally and is model dependent (Chang et al. 2000;Sutton et al. 2000).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Chang et al. 2000 source
    • cites Sutton et al. 2000 source

  • May combine two claims.

    Interpretationown data

    The Bjerknes feedback is active in the Atlantic, although it may be weaker and explains less of the variability than in the Pacific.

    “To this stage our analysis has indicated that the Bjerknes feedback is active in the Atlantic, although it may be weaker and explains less of the variability than in the Pacific.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    The equatorial Atlantic mode differs from ENSO in having significantly weaker variability, a much shorter duration (3 months) of extreme warm/cold events, and spectral characteristics hardly discernible from red noise.

    “The main differences to ENSO are the significantly weaker variability, the much shorter duration (3 months) of extreme warm/cold events, and spectral characteristics hardly discernable from red noise (Zebiak 1993;Carton and Huang 1994;Latif and Grötzner 2000).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Zebiak 1993 source
    • cites Carton and Huang 1994

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Latif and Grötzner 2000 source

  • May combine two claims.

    Premisecitation

    Coupled models that simulate ENSO-like variability in the Atlantic exist with and without flux adjustment.

    “However, coupled models that simulate ENSO-like variability in the Atlantic do exist with (Latif and Grötzner 2000) and without (Wu et al. 2002;Huang et al. 2004) flux adjustment.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Latif and Grötzner 2000 source
    • cites Wu et al. 2002

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Huang et al. 2004 source

  • May combine two claims.

    Premisecitation

    Analysis of observations in the Atlantic indicates a link between SST and surface winds to the west, and the structure of the wind response is similar to that in the Pacific.

    “Analysis of observations in the Atlantic indicates that there is a link between SST and surface winds to the west (Servain et al. 1982;Hirst and Hastenrath 1983), and that the structure of the response in the wind field is similar to that in the Pacific (Zebiak 1993).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Servain et al. 1982 source
    • cites Hirst and Hastenrath 1983

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Zebiak 1993 source

  • May combine two claims.

    Interpretationcitation

    The conflicting results from CGCMs are easily understood because the strength of equatorial coupled variability depends entirely on the ability of the model to simulate the Bjerknes feedback and its seasonality correctly, both of which depend on the climatology of the Atlantic, which is poorly simulated by such models.

    “The conflicting results from CGCMs is also easily understood, since the strength of equatorial coupled variability depends entirely on the ability of the model to simulate the Bjerknes feedback and its seasonality correctly, both of which depend on the climatology of the Atlantic, which is poorly simulated by such models (Davey et al. 2002).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Davey et al. 2002 source

  • May combine two claims.

    Interpretationreasoning

    The net feedback in the Atlantic is weaker and hence other mechanisms contribute to SST variability.

    “Thus, the answer to the first question is yes, but the net feedback is weaker and hence other mechanisms contribute to SST variability.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    Seasonal variations in the strength of the Bjerknes feedback in the Pacific are consistent with SSTAs peaking toward the end of the year, but in the Pacific the seasonality is primarily controlled by the seasonal variations in the strength of subsurface-surface interactions, which are weakest in boreal spring.

    “Seasonal variations in the strength of the Bjerknes feedback in the Pacific are consistent with SSTAs peaking toward the end of the year, but in the Pacific the seasonality is primarily controlled by the seasonal variations in the strength of subsurfacesurface interactions, which are weakest in boreal spring.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The Bjerknes feedback loop in the Atlantic is only closed during boreal spring and summer, meaning that peak equatorial SSTAs occur in boreal summer and disappear thereafter.

    “Thus the Bjerknes feedback loop in the Atlantic is only closed during boreal spring and summer, meaning that peak equatorial SSTAs occur in boreal summer and disappear thereafter.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    In the western Pacific, where SSTs are always higher than 28°C, the atmospheric sensitivity seems tied to the east-west SST contrast, which is related to lower-level convergence.

    “In the western Pacific, where SSTs are always higher than 28°C, the atmospheric sensitivity seems tied to the eastwest SST contrast (not shown), which is related to the lower-level convergence.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    Our analysis of the coupled feedbacks is entirely consistent with ICM (Zebiak 1993) and HCM studies (Latif and Barnett 1995; Nobre et al. 2003), which indicate that a damped coupled mode exists in the equatorial Atlantic.

    “Our analysis of the coupled feedbacks is entirely consistent with ICM (Zebiak 1993) and HCM studies (Latif and Barnett 1995;Nobre et al. 2003), which indicate that a damped coupled mode exists in the equatorial Atlantic.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Zebiak 1993 source
    • cites Latif and Barnett 1995

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Nobre et al. 2003 source

  • May combine two claims.

    Interpretationreasoning

    Eastern Atlantic SSTAs are primarily only affected by subsurface temperature anomalies during late boreal spring and early boreal summer, because during these months the thermocline is shallow enough that subsurface anomalies can affect SST and equatorial upwelling is strongest.

    “Eastern Atlantic SSTAs are primarily only affected by subsurface temperature anomalies during late boreal spring and early boreal summer, since during these months the thermocline is shallow enough that subsurface anomalies can affect SST and equatorial upwelling is strongest.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The strength of these interactions appears somewhat weaker in the Atlantic, and more seasonally modulated.

    “The strength of these interactions appears somewhat weaker in the Atlantic, and more seasonally modulated.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Seasonal variations in the coupling between subsurface and surface result from both variations in mean upwelling and in the mean position of the thermocline depth, because thermocline depth controls the temperature anomalies at the base of the mixed layer.

    “Thus, seasonal variations in the coupling will result from both variations in mean upwelling and in the mean position of the thermocline depth, since it will control the temperature anomalies at the base of the mixed layer [i.e., perturbations about a deeper (shallow) thermocline will produce weaker (stronger) temperature anomalies at the base of the mixed layer].”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    In the Atlantic the strongest atmospheric sensitivity to SSTAs seems related to the absolute SSTs in the western Atlantic, which only rise above 28°C in May.

    “In the Atlantic the strongest sensitivity seems related to the absolute SSTs in the western Atlantic, which only rise above 28°C in May (Fig. 4b).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    This is consistent with Atlantic SST variability being weaker, tied to boreal summer, and less long lasting than in the Pacific.

    “This is consistent with Atlantic SST variability being weaker, tied to boreal summer, and less long lasting than in the Pacific.”
    Quote in the paperSubstantial claim
44 of 44

  • The paper relies on this without support.

    The climates of the Atlantic and Pacific basins are very similar (easterly surface winds, equatorial cold tongue, upward sloping thermocline, similar annual cycles of winds and SST).

    “Despite this the climates of the two basins are very similar: easterly surface winds, an equatorial cold tongue, an upward sloping thermocline toward the east, and similar annual cycles of winds and SST.”

  • The paper relies on this without support.

    ENSO is the result of a positive ocean-atmosphere feedback (the Bjerknes feedback) and a delayed negative ocean feedback.

    “ENSO is the result of a positive ocean-atmosphere feedback, which is commonly referred to as the Bjerknes feedback, and a delayed negative ocean feedback.”

  • The paper relies on this without support.

    The equatorial Atlantic mode has a strong tendency to peak in boreal summer.

    “Another poorly understood feature of the equatorial Atlantic mode is its strong tendency to peak in boreal summer, in contrast to ENSO, which peaks in boreal winter.”

  • The paper relies on this without support.

    For subsurface temperature anomalies to affect SST, vertical advection of subsurface temperature anomalies must be an important term in the SST budget.

    “For subsurface temperature anomalies to affect SST, the vertical advection of subsurface temperature anomalies must be an important term in the SST budget.”

  • The authors state this as an assumption.

    Yearly mean data are independent of each other.

    “Yearly mean data are assumed to be independent of each other.”

  • The paper relies on this without support.

    The sea level data are of much higher quality than those derived from XBT measurements.

    “Furthermore the data are of much higher quality than those derived from XBT measurements.”

  • The paper relies on this without support.

    The first element of the Bjerknes feedback loop is the strong relationship between eastern Pacific SSTA and central Pacific surface zonal winds.

    “The first element of the Bjerknes feedback loop is the strong relationship between eastern Pacific SSTA and central Pacific surface zonal winds.”

  • The paper relies on this without support.

    Seasonal modulations of ocean-atmosphere coupling likely contribute to the seasonality of the variability.

    “In the same way, seasonal modulations of oceanatmosphere coupling also likely contribute to the seasonality of the variability.”

  • The paper relies on this without support.

    Previous studies have only investigated individual components of the Bjerknes feedback, not the full feedback and its seasonality.

    “This study differs from previous ones, in that the full Bjerknes feedback and its seasonality are estimated.Other studies have only investigated individual components.”

  • The authors state this as an assumption.

    The delay around the coupled loop is 2 months.

    “Assuming that the delay around the coupled loop is indeed 2 months, then the growth rate in the Pacific is almost twice as strong as in the Atlantic.”

  • The paper relies on this without support.

    The response of the atmosphere to SSTAs in the Tropics is highly nonlinear, involving convection that depends on both lower-level convergence and absolute SST.

    “Understanding the reasons for this seasonality is non-trivial, since the response of the atmosphere to SSTAs in the Tropics is highly nonlinear, as it involves convection, which depends on both lower-level convergence and absolute SST.”

  • The paper relies on this without support.

    The impact of surface stress anomalies on the ocean is dependent on the vertical oceanic stratification.

    “The impact of surface stress anomalies on the ocean is dependent on the vertical oceanic stratification, and thus some seasonality in ocean sensitivity to surface stress anomalies (second element of the Bjerknes feedback) may be expected.”

  • The paper relies on this without support.

    The seasonal movements of the intertropical convergence zone (ITCZ) follow the warmest SST.

    “This seasonality is determined by the seasonal movements of the intertropical convergence zone (ITCZ), which follow the warmest SST.”
13 of 13

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Figure 2b extends the ocean simulation beyond its stated end date

    Minor

    The Figure 2 caption dates the OGCM-simulated series through 2003, but the methods say the simulation used in the paper covers 1950-2001.

  • Figure 1b is dated before its satellite sea-level data begin

    Minor

    The caption assigns Figure 1b a 1950-97 period and says it uses satellite sea-level data. The methods state that those observations begin in January 1993, so they cannot cover the stated period.

2 of 2

Cites

Flagged first, then by citations

3 of the 40 references couldn’t be matched to a known paper.

Research works printed but not linked: 7

  1. da Silva, A. M., C. C.Young-Molling, and S.Levitus, 1994: Algorithms and Procedures. Vol. 1, Atlas of Surface Marine Data 1994, NOAA Atlas NESDIS 6, 83 pp.
  2. Dommenget, 2000, Interannual to decadal variability in the tropical Atlantic., J. Climate, 13, 777, 10.1175/1520-0442(2000)013<0777:ITDVIT>2.0.CO;2 · DOI
  3. Levitus, S., R.Burgett, and T. P.Boyer, 1994: Salinity. Vol. 3, World Ocean Atlas 1994, NOAA Atlas NESDIS 3, 99 pp.
  4. Ruiz-Barradas, 2000, Structure of interannual-to-decadal climate variability in the tropical Atlantic sector., J. Climate, 13, 3285, 10.1175/1520-0442(2000)013<3285:SOITDC>2.0.CO;2 · DOI
  5. Saravanan, 2000, Interaction between tropical Atlantic variability and El Niño–Southern Oscillation., J. Climate, 13, 2177, 10.1175/1520-0442(2000)013<2177:IBTAVA>2.0.CO;2 · DOI
  6. Sutton, 2000, The elements of climate variability in the tropical Atlantic region., J. Climate, 13, 3261, 10.1175/1520-0442(2000)013<3261:TEOCVI>2.0.CO;2 · DOI
  7. Wu, L., Q.Zhang, and Z.Lui, 2002: Search for the role of ENSO in tropical Atlantic variability using a coupled GCM. CLIVAR Exchanges, Vol. 7, International CLIVAR Project Office, Southampton, United Kingdom, 20–24.

Cited by

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Related

Authors
Keenlyside, N. S., & Latif, M.
Affiliations
GEOMAR Helmholtz Centre for Ocean Research Kiel (DE)
Corresponding author
Keenlyside, Noel S.
Venue
Journal of Climate
Publisher
American Meteorological Society
Published
2007-01-01
Volume
20
Issue
1
Pages
131-142
ISSN
  • 0894-8755 (ISSN-L)
  • 1520-0442
DOI
10.1175/jcli3992.1
OpenAlex
W2088402645
Semantic Scholar
0ff96614a0c1d2a5bcf320c08170cd603f71772a
Cited by
321
References
40
Citations by year
2026: 16 · 2025: 21 · 2024: 29 · 2023: 22 · 2022: 24 · 2021: 34 · 2020: 33 · 2019: 25 · 2018: 10 · 2017: 15 · 2016: 11 · 2015: 16 · 2014: 11 · 2013: 9 · 2012: 13
FWCI
6.61
Type
journal article
Language
en
Open access
Locations
  • Journal of Climate (publishedVersion)
  • Helmholtz Centre for Ocean Research Kiel (GEOMAR) (acceptedVersion, other-oa)
Funders
  • Deutsches Klimarechenzentrum
  • Bundesministerium für Bildung und Forschung (03F0443B)
Topics
  • Physical Sciences › Environmental Science › Global and Planetary Change › Climate variability and models
  • Physical Sciences › Earth and Planetary Sciences › Oceanography › Oceanographic and Atmospheric Processes
  • Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Meteorological Phenomena and Simulations
Keywords
equatorial Atlantic, interannual variability, ocean-atmosphere interaction, sea surface temperature anomalies, seasonal cycle, subsurface temperature anomalies, cross correlation function

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-16.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-16.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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