Abstract Hydraulic jumps, transitions from supercritical to subcritical flows, tend to maintain s... more Abstract Hydraulic jumps, transitions from supercritical to subcritical flows, tend to maintain suspended particles in the water column and enhance biological productivity near the surface. Transitions occur from flow adjustments as the flow moves through a cross-section reduction, such as a reef crest. Hydraulic jumps can also inhibit the settlement of coral larvae and bivalve mollusks, but could favor connectivity among reefs by dispersing planktonic organisms to surrounding areas. The Veracruz Reef System (VRS) was chosen as a case study of hydraulic jumps produced over reef crests. This system is located in the southwestern part of the Gulf of Mexico (GoM) and features 50 coral reef structures. The area is influenced by vertical stratification that modifies its dynamics. Hydrographic and yearlong current data collections in the area during 2009 identified fronts and a cyclonic recirculation. On the other hand, the presence of a hydraulic jump weakened the cyclonic recirculation on the leeward side of the reefs. The vertical gradient of the horizontal velocity suggested the influence of vertical eddies at least 35% of the time throughout the entire year. Moreover, the current velocity profiles showed a bidirectional behavior in spring and summer conditions of stratified waters. These bidirectional flows contrasted the unidirectional structure caused by frictional dynamics during northerly winds.
Three years of direct near-surface to bottom current measurements at the western Yucatan Channel ... more Three years of direct near-surface to bottom current measurements at the western Yucatan Channel (defined west of 85.6ºW) between 2008 and 2011 capture the main characteristics of the Yucatan Current. Average current structure shows a high degree of consistency over time, with mean near-surface velocities of about 1 m/s, decreasing significantly with depth. The current core position varies between 86.4ºW and 86ºW and the mean current is stronger than the variability. Below 1000m depth, current velocities are below 0.1 m/s and variations and mean flow have similar magnitude. Current velocity near the bottom increases slightly in the center of the channel, which has been shown to be related to the Loop Current dynamics. Further north, the western edge of the Loop Current was monitored with four moorings during 22 months (PE section, June 2009–April 2011); the average current there was lower than that obtained through the Yucatan Channel (0.75 m/s in its core) with variability as stron...
Three years (2008–2011) of direct current measurements from a mooring array deployedat the wester... more Three years (2008–2011) of direct current measurements from a mooring array deployedat the western Yucatan Channel (defined west of 85.6◦W) and along the eastern CampecheBank captured the main characteristics of the Yucatan and Loop Currents and the eddiesassociated with them. The array was deployed to provide upstream conditions in supportof the Loop Current Dynamics Experiment. A substantial portion (60–80%) of the varianceat the mooring sections is related to horizontal shifts of the currents due to meanders andeddies. Time-frequency analysis indicates that the velocity time-series are “event domi-nated”, with higher variability at low-frequencies (40–100 days or longer periods) but witha substantial contribution at higher frequencies (5–25 days periods) particularly strongfrom October to March. The vertical structure and time evolution of the eddy kinetic energyin a developing Campeche Bank cyclone suggest baroclinic instability dynamics are relevantfor its development. Four Loop Current eddies (Cameron, Darwin, Ekman and Franklin) sep-arated during 2008–2011. Ekman and Franklin were particularly dominated by a cycloneassociated with a meander trough of the southward flowing branch of the Loop Current(Donohue et al., 2016a,b, this issue) and weaker Campeche Bank cyclones. For Cameronand Darwin, Campeche Bank cyclonic anomalies appear to be nearly as strong as the onescoming from the eastern side of the Loop Current. Eastward shifts of the Yucatan and LoopCurrents observed over the sections appear to be linked to vorticity perturbations prop-agating from the Caribbean and precede several eddy detachments; their significance forthe generation of Campeche Bank cyclones and eddy shedding remains to be determined.Time-series of Yucatan Current transport, vorticity fluctuations and Loop Current north-ward extension during the 3 deployment periods only depict positive correlation in two ofthem. Given the wide spectrum of variability, much more data are required to determineif a statistically robust relation exists among these variables. Our results clearly illustratethe complexity of the flow in this region and that it is difficult to single out a dominantmechanism that can explain all Loop Current eddy detachments.
Mooring measurements in the Yucatan Channel, from May 2010 to May 2011 and from July 2012 to June... more Mooring measurements in the Yucatan Channel, from May 2010 to May 2011 and from July 2012 to June 2013 yield a mean transport of 27 and 25 Sv, respectively, with a subinertial standard deviation of 3.5 Sv. These mean transport values are higher than the 23 Sv reported from 21 months of similar measurements (1999–2001). Analysis of low-frequency variations of a transport proxy based on 20 years of altimetry data indicates that during 1999–2001, the flow through Yucatan Channel was anomalously low. This suggests that a sizable compensation through other channels off the Gulf of Mexico is required to match the transport cable measurements of the Florida Current at 27°N.
Abstract Hydraulic jumps, transitions from supercritical to subcritical flows, tend to maintain s... more Abstract Hydraulic jumps, transitions from supercritical to subcritical flows, tend to maintain suspended particles in the water column and enhance biological productivity near the surface. Transitions occur from flow adjustments as the flow moves through a cross-section reduction, such as a reef crest. Hydraulic jumps can also inhibit the settlement of coral larvae and bivalve mollusks, but could favor connectivity among reefs by dispersing planktonic organisms to surrounding areas. The Veracruz Reef System (VRS) was chosen as a case study of hydraulic jumps produced over reef crests. This system is located in the southwestern part of the Gulf of Mexico (GoM) and features 50 coral reef structures. The area is influenced by vertical stratification that modifies its dynamics. Hydrographic and yearlong current data collections in the area during 2009 identified fronts and a cyclonic recirculation. On the other hand, the presence of a hydraulic jump weakened the cyclonic recirculation on the leeward side of the reefs. The vertical gradient of the horizontal velocity suggested the influence of vertical eddies at least 35% of the time throughout the entire year. Moreover, the current velocity profiles showed a bidirectional behavior in spring and summer conditions of stratified waters. These bidirectional flows contrasted the unidirectional structure caused by frictional dynamics during northerly winds.
Three years of direct near-surface to bottom current measurements at the western Yucatan Channel ... more Three years of direct near-surface to bottom current measurements at the western Yucatan Channel (defined west of 85.6ºW) between 2008 and 2011 capture the main characteristics of the Yucatan Current. Average current structure shows a high degree of consistency over time, with mean near-surface velocities of about 1 m/s, decreasing significantly with depth. The current core position varies between 86.4ºW and 86ºW and the mean current is stronger than the variability. Below 1000m depth, current velocities are below 0.1 m/s and variations and mean flow have similar magnitude. Current velocity near the bottom increases slightly in the center of the channel, which has been shown to be related to the Loop Current dynamics. Further north, the western edge of the Loop Current was monitored with four moorings during 22 months (PE section, June 2009–April 2011); the average current there was lower than that obtained through the Yucatan Channel (0.75 m/s in its core) with variability as stron...
Three years (2008–2011) of direct current measurements from a mooring array deployedat the wester... more Three years (2008–2011) of direct current measurements from a mooring array deployedat the western Yucatan Channel (defined west of 85.6◦W) and along the eastern CampecheBank captured the main characteristics of the Yucatan and Loop Currents and the eddiesassociated with them. The array was deployed to provide upstream conditions in supportof the Loop Current Dynamics Experiment. A substantial portion (60–80%) of the varianceat the mooring sections is related to horizontal shifts of the currents due to meanders andeddies. Time-frequency analysis indicates that the velocity time-series are “event domi-nated”, with higher variability at low-frequencies (40–100 days or longer periods) but witha substantial contribution at higher frequencies (5–25 days periods) particularly strongfrom October to March. The vertical structure and time evolution of the eddy kinetic energyin a developing Campeche Bank cyclone suggest baroclinic instability dynamics are relevantfor its development. Four Loop Current eddies (Cameron, Darwin, Ekman and Franklin) sep-arated during 2008–2011. Ekman and Franklin were particularly dominated by a cycloneassociated with a meander trough of the southward flowing branch of the Loop Current(Donohue et al., 2016a,b, this issue) and weaker Campeche Bank cyclones. For Cameronand Darwin, Campeche Bank cyclonic anomalies appear to be nearly as strong as the onescoming from the eastern side of the Loop Current. Eastward shifts of the Yucatan and LoopCurrents observed over the sections appear to be linked to vorticity perturbations prop-agating from the Caribbean and precede several eddy detachments; their significance forthe generation of Campeche Bank cyclones and eddy shedding remains to be determined.Time-series of Yucatan Current transport, vorticity fluctuations and Loop Current north-ward extension during the 3 deployment periods only depict positive correlation in two ofthem. Given the wide spectrum of variability, much more data are required to determineif a statistically robust relation exists among these variables. Our results clearly illustratethe complexity of the flow in this region and that it is difficult to single out a dominantmechanism that can explain all Loop Current eddy detachments.
Mooring measurements in the Yucatan Channel, from May 2010 to May 2011 and from July 2012 to June... more Mooring measurements in the Yucatan Channel, from May 2010 to May 2011 and from July 2012 to June 2013 yield a mean transport of 27 and 25 Sv, respectively, with a subinertial standard deviation of 3.5 Sv. These mean transport values are higher than the 23 Sv reported from 21 months of similar measurements (1999–2001). Analysis of low-frequency variations of a transport proxy based on 20 years of altimetry data indicates that during 1999–2001, the flow through Yucatan Channel was anomalously low. This suggests that a sizable compensation through other channels off the Gulf of Mexico is required to match the transport cable measurements of the Florida Current at 27°N.
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