Deep Cycle Turbulence in Atlantic and Pacific Cold Tongues

Confidence in these measurements is justified by previous comparisons between 16-day averages of ε from shipboard profiling (using shear probes) and multiple χpods on both the TAO mooring and an additional nearby mooring that showed agreement to within a factor of 2.

“Confidence in these measurements is justified by previous comparisons between 16-day averages of ϵ from (i) shipboard profiling (using shear probes) and (ii) multiple χpods on both the TAO mooring and an additional nearby mooring that showed agreement to within a factor of 2 (Perlin & Moum, 2012).”

• cites Perlin & Moum, 2012 sourcePartly supported

  Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  Experimental — accuracy not yet measured

The influence of TIW-induced mixing on long term means is less than expected from the measurements made in 2008.

“This suggests that the influence of TIW-induced mixing on long term means is less than expected from the measurements made in 2008 (Moum et al., 2009;Inoue et al., 2012Inoue et al., , 2019)).”

• cites Moum et al., 2009 sourceNot checked — no full text of the source
• cites Inoue et al., 2012 sourceNot checked — no full text of the source
• cites Inoue et al., 2019 sourcePartly supported

  Section 6 (Summary; page unavailable) says the largest diffusivity and heat flux occurred during an anomalous fourth TIW, while Section 5.1 says the dependence of diffusivity and heat flux on TIW phase was less clear across the observed waves. These findings support caution about extrapolating from the intense 2008 event, but the paper does not assess TIW-induced mixing's influence on long-term means or compare it with expectations from those measurements. (LLM, conf=0.79)

  Experimental — accuracy not yet measured

In each case, the 50% metric occurs at roughly 1/2 the distance from the EUC core depth to the sea surface.

“In each case, the 50% metric occurs at roughly 1/2 the distance from the EUC core depth to the sea surface.”

Commonalities in the vertical structure and magnitude of the statistic %Ri < 1/4 are revealed by scaling the depth to isolate the DC layer such that the vertical coordinate is (z-MLD)/(zEUC-MLD).

“Commonalities in the vertical structure and magnitude of the statistic %Ri < 1/4 are revealed by scaling the depth (where z = -depth) to isolate the DC layer such that the vertical coordinate is (z-M LD)/(z EU C -M LD), where M LD is the depth of the ML base and z EU C is the EUC core depth (Figure 3b).”

Commonalities in the vertical structure and magnitude of ε are seen via scaling of ε by τ•Sh/ρ0, where τ is the surface wind stress, Sh is the mean value of Sh over the DC layer and ρ0 a mean water density.

“Commonalities in the vertical structure and magnitude of ϵ are seen via scaling of ϵ by τ •Sh/ρ 0 , where τ is the surface wind stress, Sh is the mean value of Sh over the DC layer and ρ 0 a mean water density (Smyth et al., 2017).”

• cites Smyth et al., 2017 sourceNot checked — no full text of the source

At 140°W, the decrease from the maximum ε to its value at EUC core depth (103 m) is a factor of 4.

“• a factor of 4 at 140 • W (EUC core at 103m).”

At and below the mean depths of the EUC core there are very few values of Ri < Ri_cr at all three locations.

“At and below the mean depths of the EUC core there are very few values of Ri < Ri cr .This is the case at all three locations (Figure 2c).”

At 140°W the maximum value of ε occurs at 40 m.

“At 140 • W the maximum value of ϵ occurs at 40m.”

Deep cycle turbulence (DCT) occurs beneath the mixed layer and above the core of the Equatorial Undercurrent (EUC) in the equatorial Atlantic and Pacific cold tongues.

“Multiyear turbulence measurements from oceanographic moorings in the equatorial Atlantic and Pacific cold tongues reveal similarities in deep cycle turbulence (DCT) beneath the ML and above the core of the Equatorial Undercurrent (EUC).”

• Also stated in: § 70 · plain

  “To summarize, DC turbulence has two defining properties: 71 (1) it occurs below the ML base, and”

At 23°W, the decrease from the maximum ε to its value at EUC core depth (73 m) is a factor of 6.

“• a factor of 6 at 23 • W (EUC core at 73m); and”

At both Atlantic sites, the maximum in ε occurs at the second χpod at 30 m.

“At both, the maximum in ϵ occurs at the second χpod at 30m.”

A proposed scaling in depth that isolates the deep cycle layers and of ε by the product of wind stress and current shear collapses vertical profiles at all sites to within a factor of 2.

“This combination of depth and amplitude scalings collapses the measurements at the three sites to within a factor of 2 at all depths.”

At 10°W, the decrease from the maximum ε to its value at EUC core depth (61 m) is a factor of 10.

“• a factor of 10 at 10 • W (EUC core at 61m);”

At the two Atlantic sites, the mean values of ε are nearly identical at the two uppermost χpods.

“At the two Atlantic sites, the mean values of ϵ, (ϵ), are nearly identical at the two uppermost χpods (Figure 2d).”

Daytime values of ε at 23°W and 10°W are roughly the same as at the 140°W site.

“Daytime values are roughly the same as at the 140 • W site.”

At 0° 140°W, modes of ε differ by more than a factor of 10 between before and after the sunset transition.

“Modes differ by more than a fac-216 tor of 10 (Figure 4d) as indicated by the averaged distributions of ϵ before (black -15:00-217 16:30) and after (blue -00:00-02:00) the sunset transition.218”

At 0° 140°W, around sunset there is an impulse-like increase in ε from daytime values to a range of values that remains relatively steady until sunrise.

“Around sunset, there is an impulse-like increase in ϵ from daytime val-214 ues to a range of values that remains relatively steady until sunrise.”

The sites at 0° 10°W and 0° 23°W exhibit the salient characteristics of the diurnal cycle of turbulence beneath the ML that we associate with DC turbulence.

“Comparisons to measurements from the PCT at 0 • 140 • W shows the sites at 0 • 10 • W and 0 • 23 • W to exhibit the salient characteristics of the diurnal cycle of turbulence beneath the ML that we associate with DC turbulence.”

The general pattern of diurnal variation of ε is repeated at both the 23°W and 10°W sites.

“This general pattern of diurnal variation of ϵ is repeated at both the 23 • W and 10 • W 219 sites (Figures 4e-i).”

At 0° 140°W, ε generally decreases from after sunrise to sunset.

“There is a general decrease in ϵ beginning after sunrise and con-213 tinuing to sunset.”

The diurnal variation of the median value of ε is apparent at all three sites at all depths to 60 m.

“The diurnal variation of the 223 median value of ϵ is apparent at all three sites at all depths to 60 m (Figure 5).”

At 0° 140°W, day-to-night increases of both means and medians of ε are about a factor of 10.

“Day to night increases 215 of both means and medians are about a factor of 10.”

The 15 years of χpod measurements at 0° 140°W show DC turbulence to be a robust feature that clearly stands out over the multiyear record.

“The 15 years of χpod measurements at 0 • 140 • W provide a different perspective of DC turbulence from the short shipboard experiments previously executed there.Most importantly, they show DC turbulence to be a robust feature that clearly stands out over the multiyear record (Figure 4).”

The comparisons support a depth scaling that isolates the relative deep cycle layers with scaling of ε by τ•Sh/ρ0.

“While depth dependence varies considerably, the comparisons also support a depth scaling that isolates the relative deep cycle layers with scaling of ϵ by τ • Sh/ρ 0 .”

A diurnal composite derived from 8 days of microstructure profiling revealed that the shear layer descends from near the surface to about 60 m at a rate close to 6 meters per hour.

“urnal composite derived from 8 days of microstructure profiling revealed that the shear 67 layer descends from near the surface to about 60 m at a rate close to 6 meters per hour 68 (Smyth et al., 2013).”

• cites Smyth et al., 2013Not matched

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

The persistent marginal instability state is nudged beyond critical toward the end of the solar day, associated with the deepening of the sheared base of the diurnal warm layer that forms during net daytime heating and deepens by shear-induced mixing.

“This persistent MI state is nudged beyond critical toward the end of the solar day, associated with the deepening of the sheared base of the diurnal warm layer that forms during the period of net daytime heating and deepens by shear-induced mixing (K.G. Hughes et al., 2021).”

• cites K.G. Hughes et al., 2021 sourceNot checked — no full text of the source

Moum et al. (1989) found the mean value of ε/(τ•Sh/ρ0) to be about 0.2 from 12 days of profiling in 1984 at 0° 140°W.

“Moum et al. (1989) found the mean value of ϵ/(τ •Sh/ρ 0 ) to be about 0.2 from 12 days of profiling in 1984 at 0 • 140 • W.”

• cites Moum et al., 1989 sourceNot checked — no full text of the source

Shipboard profiling measurements in the equatorial Pacific reveal both defining DC properties, albeit over only the cruise periods and only when profiling was rapid enough to resolve the diurnal cycle.

“Shipboard profiling measurements 76 in the equatorial Pacific (Gregg et al., 1985;Moum & Caldwell, 1985;Moum et al., 1989) 77 reveal both of the defining DC properties, albeit over only the cruise periods (typically 78 a few weeks) and only when profiling was rapid enough to resolve the diurnal cycle.”

• cites Gregg et al., 1985 sourceNot checked — no full text of the source
• cites Moum & Caldwell, 1985 sourceNot checked — no full text of the source
• cites Moum et al., 1989 sourceNot checked — no full text of the source

The existence of DC turbulence is linked to the strongly sheared current system above the EUC core where the gradient Richardson number (Ri) persistently maintains a near-critical state with values fluctuating around 0.25.

“The existence of DC turbulence is linked to the strongly sheared current system above the core of the Equatorial Undercurrent (EUC) where the gradient Richardson number (Ri) persistently maintains a near-critical state with values fluctuating around 0.25 (Smyth & Moum, 2013), a state of marginal instability (MI).”

• cites Smyth & Moum, 2013Not matched

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

The uppermost χpods at all three locations are significantly deeper than the 90th percentile of ML depths.

“The uppermost χpods at all three locations are significantly deeper 209 than the 90 th percentile of ML depths.210”

The present value 0.2 is therefore more representative of the climatology of the cold tongues.

“The present value 0.2 is therefore more representative of the climatology of the cold tongues.”

The delayed and reduced transition with depth is consistent with DC turbulence being a cycle triggered by surface changes.

“which is consistent with DC turbulence being a cycle triggered by surface 226 changes.227”

The apparent bimodal structure is largely associated with an additional dependence on the magnitude of the local wind stress that controls the timing of the transition.

“Elsewhere, we show that this apparent bimodal structure is largely associated with an additional dependence on the magnitude of the local wind stress that controls the timing of the transition (Moum et al., 2022).”

• cites Moum et al., 2022Not matched

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