Seasonal cycle in the upper equatorial Atlantic Ocean

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

These results on baroclinic mode dominance are consistent with previous studies.

“These results are consistent with previous studies [du Penhoat and Treguier, 1985;Illig et al., 2004;Thierry et al., 2004;Brandt and Eden, 2005].”

• cites du Penhoat and Treguier, 1985 sourceNot checked — no full text of the source
• cites Illig et al., 2004 sourceSupported
• cites Thierry et al., 2004Not matched

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

May combine two claims.

The models used here are all low resolution and do not capture Tropical Instability Waves, which are important in the Tropical Atlantic.

“In addition, the models used here are all low resolution and do not capture Tropical Instability Waves, which are important in the Tropical Atlantic [von Schuckmann et al., 2008].”

• cites von Schuckmann et al., 2008 sourceSupported

May combine two claims.

Distinctive features of the seasonal cycle in the upper equatorial Atlantic are strong annual and semiannual components: eastward (westward) propagating sea surface height and thermocline depth at the equator (off the equator) and westward propagating surface zonal currents at the equator.

“Distinctive features of the seasonal cycle are strong annual and semiannual components: eastward (westward) propagating sea surface height (SSH) and thermocline depth at the equator (off the equator) and westward propagating surface zonal currents at the equator.”

May combine two claims.

Nonlinear terms weaken the variability and improve the phase and zonal extent of surface zonal currents at the equator.

“While firstorder linear theory can also explain the structure of the seasonal cycle of surface zonal currents at the equator, nonlinear terms are required; they weaken the variability and improve its phase and zonal extent.”

May combine two claims.

The seasonal cycle of sea surface temperature in both basins, although exhibiting similarities in phase and strength, displays distinct relationships to zonal wind stress.

“The seasonal cycle of SST in both basins, although exhibiting similarities in phase and strength (Figures 1c and 1d), display distinct relationships to zonal wind stress (Figures 1a and 1b).”

May combine two claims.

The westward propagation of the positive anomaly at the beginning of the year along 4°S is as observed, but it is stronger and slightly phase shifted, especially in the west.

“The westward propagation of the positive anomaly at the beginning of the year is as observed, but it is stronger and slightly phase shifted, especially in the west.”

May combine two claims.

The nonlinear terms weaken the linear terms and lead to realistic zonal currents strength and they also cause the eastward currents anomaly to extend along the entire equator in September and October.

“They weaken the linear terms and lead to realistic zonal currents strength and they also cause the eastward currents anomaly to extend along the entire equator in September and October.”

May combine two claims.

The signal of the basin mode is clear from March until about August and then becomes less clear.

“The signal of the basin mode is clear from March until about August and then becomes less clear (Figure 3a).”

May combine two claims.

Both the OGCM and IOM reproduce the seasonal cycle in sea surface height on and off the equator well.

“Both the OGCM and IOM reproduce the seasonal cycle in SSH on and off the equator well (Figure 4).”

May combine two claims.

In the east when zonal wind stress strengthens in April, the eastward zonal currents anomaly reverses sign and propagates westward along the equator.

“In the east when zonal wind stress strengthens in April (Figure 1b), the eastward zonal currents anomaly reverses sign and propagates westward along the equator.”

May combine two claims.

The eastward anomaly extends almost simultaneously across the whole equatorial Atlantic, although the amplitude varies with longitude, being stronger between about 20°W and 0°W.

“The eastward anomaly extends almost simultaneously across the whole equatorial Atlantic, although the amplitude varies with longitude, being stronger between about 20°W and 0°W.”

May combine two claims.

Meridional advection is strong from June to October and weak from January to May.

“Meridional advection, which is related to variations in both meridional currents and meridional variation of zonal currents, is strong (weak) from June to October (January -May).”

May combine two claims.

The deepening of the thermocline in the west in September also propagates eastward, but the propagation is much more rapid than for the shoaling.

“The deepening of the thermocline in the west in September also propagates eastward, but the propagation is much more rapid than for the shoaling (Figure 1f).”

May combine two claims.

At the equator the annual cycle in the west and semiannual cycle in the east are simulated by both models, including the rapid sea-level decrease in the cold tongue during boreal summer, and the basin-wide increase in sea level in September and October.

“In particular, at the equator the annual cycle in the west and semiannual cycle in the east are simulated by both models (Figures 4a and 4d), including the rapid sealevel decrease in the cold tongue during boreal summer, and the basin-wide increase in sea level in September and October.”

May combine two claims.

The observed westward propagation and semiannual cycle are captured by the linear solution, except in September and October when the linear solution is unable to reproduce the observed basin-wide eastward currents anomalies.

“In particular, the observed westward propagation and semiannual cycle are captured, except in September and October when the linear solution is unable to reproduce the observed basin wide eastward currents anomalies.”

May combine two claims.

The nonlinear terms have equal magnitude to linear terms and play an important role.

“Comparing total, linear and nonlinear surface zonal currents (Figures 5b-5d), shows that the nonlinear terms have equal magnitude to linear terms and play an important role.”

May combine two claims.

In the west the annual cycle is dominant, with minimum thermocline depth occurring in May and maximum in September.

“In the west the annual cycle is dominant, with minimum (maximum) depth occurring in May (September).”

May combine two claims.

Seasonal variations in thermocline depth have larger amplitude on the eastern and western sides of the basin, rather than at the center, and are about 90° out of phase from March to July.

“An interesting aspect is that seasonal variations have larger amplitude on the eastern and western sides of the basin, rather than at the center and are about 90° out of phase from March to July (Figure 1f), which is reminiscent of the basin mode [Cane and Moore, 1981].”

• cites Cane and Moore, 1981 sourceNot checked — no full text of the source

May combine two claims.

Along 4°N, both models reproduce the basic pattern of the seasonal cycle, prominent annual and semiannual cycles in the west and east, respectively.

“Along 4°N, despite being generally too weak, both models (Figures 4b and 4e) reproduce the basic pattern of the seasonal cycle (Figure 2b), prominent annual and semiannual cycles in the west and east, respectively.”

May combine two claims.

MPI-OM surface zonal currents display a westward propagation from September to December, but observed currents are almost stationary.

“Another difference is that MPI-OM surface zonal currents display a westward propagation from September to December, but observed currents are almost stationary; however, this may be partly due to different periods considered (section 2).”

May combine two claims.

Off the equator, sea surface height also exhibits a pronounced seasonal cycle, with significant annual and semiannual cycles in the west and east, respectively, similar to that at the equator.

“Off the equator, SSH also exhibit a pronounced seasonal cycle (Figures 2b and 2c), with significant annual and semiannual cycles in the west and east, respectively, similar to that at the equator.”

May combine two claims.

The driving terms are meridional and vertical advection, while vertical diffusion dissipates nonlinear velocity.

“The driving terms are meridional and vertical advection, while vertical diffusion dissipates nonlinear velocity.”

May combine two claims.

The shallow thermocline in April-May progresses eastward and reaches the Gulf of Guinea in boreal summer, when the thermocline depth there decreases by almost half.

“The shallow thermocline in April -May progresses eastward and reaches the Gulf of Guinea in boreal summer, when the thermocline depth there decreases by almost half (not shown).”

May combine two claims.

The annual mean equatorial thermocline slopes upward toward the east, and is around 100 m in the west and 50 m in the east.

“The annual mean equatorial thermocline slopes upward toward the east, and is around 100 m in the west and 50 m in the east (not shown).”

May combine two claims.

The seasonal cycle of surface zonal currents along the equator in the Atlantic is dominated by a semiannual cycle and is strongest in the central part of the basin.

“The seasonal cycle of surface zonal currents along the equator in the Atlantic is dominated by a semiannual cycle and is strongest in the central part of the basin (Figure 1h) [Richardson and McKee, 1984].”

• cites Richardson and McKee, 1984 sourceNot checked — no full text of the source

May combine two claims.

In the western Atlantic the seasonal cycle in zonal wind stress is dominated by an annual cycle, while in the east a semiannual cycle is apparent.

“In the western Atlantic the seasonal cycle in zonal wind stress (Figure 1b) is dominated by an annual cycle, while in the east a semiannual cycle is apparent.”

May combine two claims.

At the beginning of the year, the zonal current anomaly is eastward in the east and weak and westward in the west.

“At the beginning of the year, the zonal current anomaly is eastward (weak and westward) in the east (west).”

May combine two claims.

Toward the east a semiannual cycle also appears in the thermocline variability, and in the far east it is almost as strong as the annual cycle.

“Toward the east a semiannual cycle also appears in the thermocline variability, and in the far east it is almost as strong as the annual cycle.”

May combine two claims.

The most significant terms in the nonlinear equations are meridional advection, vertical diffusion, and vertical advection; zonal advection is negligible.

“The most significant terms are meridional advection, vertical diffusion, and vertical advection; zonal advection is negligible (Figure 6).”

May combine two claims.

At eastern and western boundaries, Kelvin and Rossby wave contributions are in phase with each other, indicating the importance of boundary reflections.

“At eastern and western boundaries, Kelvin and Rossby wave contributions are in phase with each other, indicating the importance of boundary reflections [Schouten et al., 2005].”

• cites Schouten et al., 2005 sourceNot checked — no full text of the source

May combine two claims.

The contribution of Kelvin and Rossby waves to the solution is comparable in the west, but in the east the Kelvin wave contribution is about three times larger.

“The contribution of Kelvin (Figure 7b) and Rossby (Figure 7c) waves to the solution is comparable in the west, but in the east the Kelvin wave contribution is about three times larger.”

May combine two claims.

For sea surface height, the second baroclinic mode is dominant, but for surface currents the second and third modes are most important.

“For SSH, the second mode is dominant, but for surface currents the second and third ones are most important.”

May combine two claims.

At the peak of the positive phase, the zonal currents are weak and the zonal east-west gradient is at its maximum.

“At the peak of the positive phase (Figure 3b), the zonal currents are weak and the zonal east -west gradient is at its maximum.”

May combine two claims.

The models correctly simulate a semiannual cycle along the whole equatorial Atlantic, including the boreal summer westward currents anomalies and their westward propagation.

“In particular, the models correctly simulate a semiannual cycle along the whole equatorial Atlantic, including the boreal summer westward currents anomalies and their westward propagation.”

May combine two claims.

For SSH at the equator, both Kelvin and Rossby wave contributions are significant, but the Kelvin wave contribution dominates and results in eastward propagation.

“For SSH at the equator, both Kelvin and Rossby wave contributions are significant, but the Kelvin wave contribution dominates and results in eastward propagation.”

May combine two claims.

Modelling results show that Kelvin and Rossby waves are both important at the equator.

“However, modelling results here show that Kelvin and Rossby waves are both important at the equator.”

May combine two claims.

The most significant nonlinear terms are meridional advection, vertical diffusion, and vertical advection.

“The most significant terms are meridional advection, vertical diffusion, and vertical advection; zonal advection is negligible.”

May combine two claims.

At the equator, variations propagate eastward, but westward at 4°N and 4°S.

“At the equator, variations propagate eastward, but westward at 4°N and 4°S.”

May combine two claims.

Although linear theory can explain the phase and east-west propagation of surface zonal currents at the equator, variations are far too strong.

“Although linear theory can explain the phase and east -west propagation of the latter, variations are far too strong.”

May combine two claims.

Surface zonal currents at the equator exhibit a dominant semiannual cycle with westward propagation.

“Surface zonal currents at the equator exhibit a dominant semiannual cycle with westward propagation.”

May combine two claims.

Nonlinear terms weaken the variability to observed levels, and improve its phase and zonal extent.

“Here, nonlinear terms were shown to weaken the variability to observed levels, and improve its phase and zonal extent.”

May combine two claims.

There are some differences between simulated and observed sea surface height variations; for example, at the end of the year in the east, a negative signal is simulated, while a positive one is observed, and simulated variability in the west is stronger than observed.

“There are some differences between simulated and observed SSH variations.For example, at the end of the year in the east, a negative signal is simulated, while a positive one is observed.Simulated variability in the west is also stronger than observed.”

May combine two claims.

The basin mode features are most prominent in observations from March-August and less prominent from September-February.

“From March -August (September -February) the semiannual and annual components constructively (destructively) interfere and the basin mode features are most (less) prominent in observations.”

May combine two claims.

Seasonal variations in thermocline depth and sea level display prominent annual and semiannual cycles in the west and east, respectively.

“Seasonal variations in thermocline depth and sea level display prominent annual and semiannual cycles in the west and east, respectively.”

May combine two claims.

From March-August the semiannual and annual components constructively interfere; from September-February they destructively interfere.

“From March -August (September -February) the semiannual and annual components constructively (destructively) interfere and the basin mode features are most (less) prominent in observations.”

May combine two claims.

Vertical advection of momentum brings more eastward momentum to the surface layer and reduces the westward momentum in the cold tongue when upwelling is stronger in boreal summer.

“In particular, vertical advection of momentum brings more eastward momentum to the surface layer and reduces the westward momentum in the cold tongue when upwelling is stronger in boreal summer.”

May combine two claims.

The linear solution is essentially reproduced by the first four baroclinic modes, although the second and third are dominant.

“The linear solution is essentially reproduced by the first four baroclinic modes, although the second and third are dominant.”

May combine two claims.

In the Atlantic, both thermocline depth and surface zonal current exhibit strong annual and semiannual components, whereas in the Pacific the annual harmonic dominates.

“Furthermore, in the Atlantic both quantities exhibit strong annual and semiannual components, whereas in the Pacific the annual harmonic dominates.”

May combine two claims.

In the Pacific, sea surface temperature and zonal wind stress variations are consistent with a mixed layer mode, but they are not in the Atlantic.

“In the Pacific, SST and zonal wind stress variations are consistent with a mixed layer mode [e.g., Chang and Philander, 1994;Xie, 1994], but they are not in the Atlantic.”

• cites Chang and Philander, 1994 sourceNot checked — no full text of the source
• cites Xie, 1994Not matched

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

Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

The failure in simulating the South Equatorial Current is probably due to nonlinear dynamics, for instance vertical advection.

“They speculated that the failure in simulating SEC is probably due to nonlinear dynamics, for instance vertical advection [Philander and Pacanowski, 1980].”

• cites Philander and Pacanowski, 1980 sourceNot checked — no full text of the source

May combine two claims.

As interannual variability is weak in comparison to the seasonal cycle, the PIRATA data, although short, are sufficient to describe the seasonal cycle.

“As interannual variability is weak in comparison to the seasonal cycle, the data although short are sufficient to describe the seasonal cycle.”

May combine two claims.

In the equatorial Atlantic, sea surface temperature variability is dominated by the seasonal cycle, while interannual fluctuations are comparatively weak.

“In the equatorial Atlantic, sea surface temperature (SST) variability is dominated by the seasonal cycle, while interannual fluctuations are comparatively weak [Xie and Carton, 2004].”

• cites Xie and Carton, 2004Not matched

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

Classified as probably not a substantial claim. May combine two claims.

Sea surface height propagates eastward at the equator and westward off the equator.

“One is that sea surface height propagates eastward at the equator and westward off the equator, as shown by Schouten et al. [2005].”

• cites Schouten et al., 2005 sourceNot checked — no full text of the source

May combine two claims.

Linear dynamics can simulate the seasonal variability in the North Equatorial Countercurrent, but not in the equatorial branch of the South Equatorial Current.

“du Penhoat and Treguier [1985] showed that linear dynamics can simulate the seasonal variability in NECC, but not in the equatorial branch of SEC.”

• cites du Penhoat and Treguier, 1985Not matched

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

May combine two claims.

The sea surface temperature, thermocline depth and zonal current fluctuations exhibit quite different relationships in the Atlantic and Pacific, as does the seasonal heat budget of the mixed layer.

“The SST, thermocline depth and zonal current fluctuations also exhibit quite different relationships in the Atlantic and Pacific, as are the seasonal heat budget of the mixed layer [e.g., Wang and McPhaden, 1999;Foltz et al., 2003].”

• cites Wang and McPhaden, 1999 sourceNot checked — no full text of the source
• cites Foltz et al., 2003 sourceNot checked — no full text of the source

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

A similar argument was previously used to explain the strong semiannual signal in the deep tropical Atlantic.

“A similar argument was previously used to explain the strong semiannual signal in the deep tropical Atlantic [Thierry et al., 2004].”

• cites Thierry et al., 2004Not matched

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

Classified as probably not a substantial claim.

There is a discrepancy between theoretical Kelvin wave phase speeds and the eastward propagation of sea level along the equator during boreal summer.

“However, Bunge and Clarke [2009] found a discrepancy between theoretical Kelvin waves phase speeds and the eastward propagation of sea level along the equator during boreal summer.”

• cites Bunge and Clarke, 2009 sourceNot checked — no full text of the source

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

Weisberg and Tang also made the same assumption of negligible boundary influence and were successful in reproducing many features of seasonal variations of the thermocline at the equator.

“Weisberg and Tang [1983, 1985, 1987, 1990] also made the same assumption and were successful in reproducing many features of seasonal variations of the thermocline at the equator.”

• cites Weisberg and Tang, 1983, 1985, 1987, 1990Not matched

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

• AssumptionThe authors state this as an assumption: The influence from the Gulf of Guinea and Brazilian coast on the propagation of planetary waves at the equator is negligible.

May combine two claims.

In boreal summer, when upwelling is stronger following the intensification of the surface trades, vertical advection of momentum brings more eastward momentum to the surface layer and reduces the westward momentum.

“In boreal summer, for example, when upwelling is stronger following the intensification of the surface trades, vertical advection of momentum brings more eastward momentum to the surface layer and reduces the westward momentum.”

May combine two claims.

The gradient drives westward currents that in turn weaken the gradient.

“The gradient drives westward currents that in turn weaken the gradient.”

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

The result that vertical advection brings more eastward momentum to the surface layer and reduces westward momentum is consistent with Philander and Pacanowski [1980].

“This is consistent with Philander and Pacanowski [1980].”

• cites Philander and Pacanowski, 1980 sourceNot checked — no full text of the source

May combine two claims.

Vertical advection is controlled by changes in upwelling, which follow changes in zonal wind.

“Vertical advection is controlled by changes in upwelling, which follow changes in zonal wind (Figure 1b).”

May combine two claims.

In the tropics sea level and thermocline variations are closely related, and the observed sea-surface variations at the equator corroborate the picture from PIRATA.

“In the tropics sea level and thermocline variations are closely related, and the observed sea-surface variations at the equator (Figure 2a) corroborate the picture from PIRATA.”

• AssumptionRests on an assumption: In the tropics, sea surface height and thermocline depth variations are closely related.

May combine two claims.

In April, westward stress firstly appears in the eastern part and then moves westward.

“In April, westward stress firstly appears in the eastern part and then moves westward [Picaut, 1983].”

• cites Picaut, 1983Not matched

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

May combine two claims.

The nonlinear terms provide a necessary correction to the linear solution, contributing significantly to the strength and phase of simulated currents.

“Thus, the nonlinear terms provide a necessary correction to the linear solution, contributing significantly to the strength and phase of simulated currents.”

May combine two claims.

A deficiency of both models is that simulated sea surface height variations are too weak, and in the west they lead observations by about one month and are in phase with the zonal wind variations.

“A deficiency of both models is that simulated SSH variations are too weak, and in the west they lead observations by about one month and are in phase with the zonal wind variations; a problem previously noted [Philander and Pacanowski, 1986].”

• cites Philander and Pacanowski, 1986 sourceNot checked — no full text of the source

May combine two claims.

The seasonal cycle of SST in the equatorial Atlantic and Pacific are similar, but the dynamics are likely very different.

“First, they imply that although the seasonal cycle of SST in the equatorial Atlantic and Pacific are similar, the dynamics are likely very different.”

May combine two claims.

Sea level variability, especially at 4°N, is slightly underestimated and not always in exact phase with observations in both the IOM and OGCM.

“For example, sea level variability, especially at 4°N, is slightly underestimated and not always in exact phase with observations in both the IOM and OGCM.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

The difference in dynamics between the Atlantic and Pacific may be partly due to different basin sizes.

“This difference maybe partly due to the different basin sizes.”

Classified as probably not a substantial claim.

Bunge and Clarke (2009) found that eastward propagation of sea level from April to July at the equator is too slow compared to theoretical phase speeds of Kelvin waves of the first few baroclinic modes.

“Bunge and Clarke [2009] found that eastward propagation of sea level from April to July at the equator is too slow compared to theoretical phase speeds of Kelvin waves of the first few baroclinic modes.”

• cites Bunge and Clarke, 2009 sourceNot checked — no full text of the source

May combine two claims.

The modelling results show that linear dynamics can explain the phase and propagation characteristics in the seasonal variation of sea level and also get key features of surface zonal current variations.

“The modelling results here show that linear dynamics can explain the phase and propagation characteristics in the seasonal variation of sea level and also get key features of surface zonal current variations.”

May combine two claims.

They are reflected as a Kelvin wave on the western boundary and propagate eastward through the whole basin in September and October at the equator.

“They are reflected as a Kelvin wave on the western boundary and propagate eastward through the whole basin in September and October at the equator.”

• cites Schouten et al., 2005 sourceNot checked — no full text of the source

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

Yu and McPhaden (1999) reached a similar conclusion for the Pacific.

“Yu and McPhaden [1999] reached a similar conclusion for the Pacific.”

• cites Yu and McPhaden, 1999Not matched

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

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

In the Pacific, boundary reflections are not important.

“This is in contrast to the Pacific, where boundary reflections are not important [e.g., Yu and McPhaden, 1999].”

• cites Yu and McPhaden, 1999Not matched

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