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Estuarine and coastal geomorphology, biogeochemistry, water quality, and coastal food webs in river-dominated shelves of the Gulf of Mexico (GoM) are modulated by transport processes associated with river inputs, winds, waves, tides, and deep-ocean/continental shelf interactions. For instance, transport processes control the fate of river-borne sediments, which in turn affect coastal land loss. Similarly, transport of freshwater, nutrients, and carbon control the dynamics of eutrophication, hypoxia, harmful algal blooms, and coastal acidification. Further, freshwater inflow transports pesticides, herbicides, heavy metals, and oil into receiving estuaries and coastal systems. Lastly, transport processes along the continuum from the rivers and estuaries to coastal and shelf areas and adjacent open ocean (abbreviated herein as “river-estuary-shelf-ocean”) regulate the movements of organisms, including the spatial distributions of individuals and the exchange of genetic information between distinct subpopulations. The Gulf of Mexico Research Initiative (GoMRI) provided unprecedented opportunities to study transport processes along the river-estuary-shelf-ocean continuum in the GoM. The understanding of transport at multiple spatial and temporal scales in this topographically and dynamically complex marginal sea was improved, allowing for more accurate forecasting of the fate of oil and other constituents. For this review, we focus on five specific transport themes: (i) wetland, estuary, and shelf exchanges; (ii) river-estuary coupling; (iii) nearshore and inlet processes; (iv) open ocean transport processes; and (v) river-induced fronts and cross-basin transport. We then discuss the relevancy of GoMRI findings on the transport processes for ecological connectivity and oil transport and fate. We also examine the implications of new findings for informing the response to future oil spills, and the management of coastal resources and ecosystems. Lastly, we summarize the research gaps identified in the many studies and offer recommendations for continuing the momentum of the research provided by the GoMRI effort. A number of uncertainties were identified that occurred in multiple settings. These include the quantification of sediment, carbon, dissolved gasses and nutrient fluxes during storms, consistent specification of the various external forcings used in analyses, methods for smooth integration of multiscale advection mechanisms across different flow regimes, dynamic coupling of the atmosphere with sub-mesoscale and mesoscale phenomena, and methods for simulating finer-scale dynamics over long time periods. Addressing these uncertainties would allow the scientific community to be better prepared to predict the fate of hydrocarbons and their impacts to the coastal ocean, rivers, and marshes in the event of another spill in the GoM.

Time series of current velocity profiles were obtained at the mouth and head of a Brazilian subtropical estuary, the Ararangua, to study its dry-period response to fortnightly tidal forcing, river pulses and wind forcing. The Ararangua exemplifies a series of river-dominated estuaries along southern Brazil with widths 30 m3/s but 200 m3/s appeared in two other occasions late in the observation period and caused seaward flushing of the entire system. Overall, the estuarine circulation resembled that of a fjord when river discharge was moderate and weaker: an active upper layer driven by river discharge moving over a semi-stagnant lower layer. Strongest subtidal exchange developed ∼2–3 days after neap tides, in contrast to other studies where fortnightly modulation is determined by vertical mixing from tides. In the lower estuary, subtidal flows seemed to result from a combination of vertical mixing, from tides and wind, and from tidal advection. Moreover, the lower estuary was much more sensitive to wind forcing than the upper estuary. The upper estuary responded preferentially to river discharge and tidal forcing.

ADCP data on both sides of the island in ASCII format All files are from the East Side of the Island (July 25-27, 2018), except for "West_Side_0_000_ASC.TXT" (Jul 28-29, 2018). The files are readily readable and their format follows the default from the WinRiver software of Teledyne Instruments &nbsp

Intertidal creeks (

Data sets used and codes for figures

Hurricane Harvey reached Category 4 when it made landfall on the coast of Texas in late August 2017. Harvey not only affected the coastal region with wind speeds that peaked near 50 m/s, it also dumped ~7.6 × 1010 m3 of rain over 3 days. This rainfall was equivalent to the discharge of the Amazon River over the same period and made Harvey the wettest tropical cyclone to affect the United States. Winds and rainfall interacted to produce atypical storm surges along the coast and estuaries of Texas and compound flooding in the Houston region. Data from the NOAA's Center for Operational Oceanographic Products and Services provided information on water levels in this region. The highest water levels, 3 m above predicted, occurred from August 27th to 29th at Buffalo Bayou in the uppermost reaches of the Galveston-Trinity-Tabbs-Burnet Bay system. The peak surge occurred on Aug 29th because of the triple punch of a) the ocean wind stress and corresponding surge, plus the rainfall-related land-derived discharge from b) Buffalo Bayou and then from c) the San Jacinto River. Winds from the ocean persisted during that 3-day period and drove onshore water transport. This transport, together with anomalously high mean sea levels and the coastline modifications in the upper bay system, delayed the seaward motion of the land-derived discharge. Numerical model simulations that turned forcings on and off, highlighted the importance of the two river pulses in causing the widespread flooding. Simulations also underscored the influence of the interaction between land-derived discharge and ocean-derived surge along different parts of the Houston-Galveston Bay system.

Model output.&nbsp

The Pulley Ridge and Dry Tortugas coral reefs are among the most pristine, but also fragile, marine ecosystems of the continental United States. Understanding connectivity processes between them and with surrounding shelf and deep areas is fundamental for their management. This study focuses on the physical processes related to the connectivity of these reefs. Unprecedented in situ time series were used at these specific reef locations, together with satellite observations and numerical simulations, to investigate the dynamics controlling local circulation on the Southwestern Florida Shelf (SWFS) under oceanic influence. The approach of the Loop Current and Florida Current (LC/FC) system to the SWFS slope can induce 0.5 to 1 m/s offshore flows impacting the Pulley Ridge and Dry Tortugas reefs. On the other hand, when the LC/FC system retreats from the slope, onshore flows can carry open-sea waters over the coral reefs. Local formation of cyclonic eddies is possible near the Dry Tortugas reefs in the LC approach case and passage of upstream LC Frontal Eddies is possible in the LC retreat case. Offshore currents ∼1 m/s over the SWFS slope were also found during periods of anticyclonic LC Eddy separation. A novel finding is the shedding and northward propagation of mesoscale anticyclonic eddies from the core of the LC along the West Florida Shelf. Eddy shedding may have a broader effect on the dynamics of the shelf around the study reef areas. Long periods of LC/FC domination over these coral reefs (reaching several weeks to months) are characterized by strong (∼1 m/s) along-shelf currents and continuous upwelling processes, which may weaken the slope stratification and bring colder, deeper waters over the shelf-break and toward the shallower shelf region.

We extend the 3D unstructured-grid model previously developed for the Upper Chesapeake Bay to cover the entire Bay and its adjacent shelf, and assess its skill in simulating saltwater intrusion and the coastal plume. Recently developed techniques, including a flexible vertical grid system and a 2nd-order, monotone and implicit transport solver are critical in successfully capturing the baroclinic responses. Most importantly, good accuracy is achieved through an accurate representation of the underlying bathymetry, without any smoothing. The model in general exhibits a good skill for all hydrodynamic variables: the averaged root-mean-square errors (RMSE's) in the Bay are 9 cm for sub-tidal frequency elevation, 17 cm/s for 3D velocity time series, 1.5 PSU and 1.9 PSU for surface and bottom salinity respectively, 1.1 °C and 1.6 °C for surface and bottom temperature respectively. On the shelf, the average RMSE for the surface temperature is 1.4 °C. We highlight, through results from sensitivity tests, the central role played by bathymetry in this estuarine system and the detrimental effects, from a common class of bathymetry smoothers, on volumetric and tracer fluxes as well as key processes such as the channel-shoal contrast in the estuary and plume propagation in the coast.

Seasonal variation in the acoustic presence of blue whale calls has been widely reported for feeding grounds worldwide, however variation over the submonthly scale (several days to

Sea-level rise should cause salt-water intrusion into coastal aquifers and limit fresh submarine groundwater discharge. Pargos Spring offshore of Puerto Morelos, Quintana Roo, Mexico, intermittently discharges brackish water and allows intrusion of lagoon water with seawater salinity to the aquifer. Lagoon water intrusion occurred when sea level was > 0.08 m above mean observed values during the study period. Salt water intrusion will be permanent within a few decades at the current eustatic sea-level rise rate of ∼ 3 mm/yr. A mixing model demonstrates that oxygen dissolved in the lagoon water is reduced as it intrudes the spring. Dissolved oxygen (DO) reduction is greater at the spring vent than at sensors ∼ 10 m inside the conduit, reflecting rapid reaction kinetics. DO reduction results from organic carbon remineralization, which also releases N and P to the water. Increased frequency of intrusion events or continuous intrusion may alter microbially mediated biogeochemical reactions, thereby increasing aquifer vulnerability to sea-level rise.

Transverse variations of tidal and subtidal flow were investigated in a macrotidal and convergent estuary. This was accomplished by combining data analysis of current velocities and water density with numerical modeling at the mid-reaches of the Gironde Estuary (France). Nonlinear mechanisms responsible for overtide generation and hence subtidal flows were found to vary across the estuary and from neap to spring tides. Subtidal flows were driven by a combination of internal asymmetry, tidal advective accelerations, nonlinear effects of water level variations, quadratic friction, and river discharge. The quarter-diurnal overtide band (D4) in the flow was generated by internal asymmetry and tidal advective accelerations during neap tide. The ratio of quarter-diurnal to squared semidiurnal bands (D4/D22) was largest (>0.3) in sections of the channel showing subtidal outflow. River discharge increased from neap to spring tides causing a subsequent increase of seaward subtidal currents. During spring tide, D4 was generated by tidal advective accelerations and quadratic friction combined with river discharge, rather than by internal asymmetry. The sixth-diurnal overtide (D6) in the flow was comparable to D4 for both neap and spring tides. Largest D6/D23 ratios were found in the shallowest cross-channel locations during both neap and spring tides.

Regional sea level rise (SLR) acceleration during the past few decades north of Cape Hatteras has commonly been attributed to weakening Atlantic Meridional Overturning Circulation, although this causal link remains debated. In contrast to this pattern, we demonstrate that SLR decelerated north of Cape Hatteras and accelerated south of the Cape to >20 mm/yr, > 3 times the global mean values from 2011 to 2015. Tide gauge records reveal comparable short-lived, rapid SLR accelerations (hot spots) that have occurred repeatedly over ~1500 km stretches of the coastline during the past 95 years, with variable latitudinal position. Our analysis indicates that the cumulative (time-integrated) effects of the North Atlantic Oscillation determine the latitudinal position of these SLR hot spots, while a cumulative El Nino index is associated with their timing. The superposition of these two ocean-atmospheric processes accounts for 87% of the variance in the spatiotemporal pattern of intradecadal sea level oscillations.

Eddy viscosity parameterizations that depend on a gradient Richardson number Ri have been most pertinent to the open ocean. Parameterizations applicable to stratified coastal regions typically require implementation of a numerical model. Two novel parameterizations of the vertical eddy viscosity, based on Ri, are proposed here for coastal waters. One turbulence closure considers temporal changes in stratification and bottom stress and is coined the ‘regular fit'. The alternative approach, named the ‘lateral fit', incorporates variability of lateral flows that are prevalent in estuaries. The two turbulence parameterization schemes are tested using data from a Self Contained Autonomous Microstructure Profiler (SCAMP) and an Acoustic Doppler Current Profiler (ADCP) collected in the James River Estuary. The ‘regular fit' compares favorably to SCAMP-derived vertical eddy viscosity values but only at relatively small values of gradient Ri . On the other hand, the ‘lateral fit' succeeds at describing the lateral variability of eddy viscosity over a wide range of Ri. The modifications proposed to Ri-dependent eddy viscosity parameterizations allow applicability to stratified coastal regions, particularly in wide estuaries, without requiring implementation of a numerical model.

Analysis of 20-year time series of water levels in the northeastern Gulf of Mexico has revealed that meteotsunamis are ubiquitous in this region. On average, 1–3 meteotsunamis with wave heights >0.5 m occur each year in this area. The probability of meteotsunami occurrence is highest during March–April and June–August. Meteotsunamis in the northeastern Gulf of Mexico can be triggered by winter and summer extra-tropical storms and by tropical cyclones. In northwestern Florida most of the events are triggered by winter storms, while in west and southwest Florida they appear both in winter and summer. Atmospheric pressure and wind anomalies (periods

As a result of climate change, the frequency of glacial lake outburst floods (GLOF) is increasing in Chilean Patagonia. Yet, the impacts of the flood events on the physics and biology of fjords is still unknown. Current velocities, density, in-situ zooplankton samples, and volume backscatter (Sv) derived from an acoustic profiler were used to explore the response of circulation and zooplankton abundance in a Patagonian fjord to GLOF events in 2010 and 2014. Maximum Sv was found both during the GLOFs and in late winter to early spring of 2010 and the fall and summer of 2014. The increase in Sv in late winter and spring of 2010 corresponded to multiple zooplankton species found from in-situ net sampling. In addition, diel vertical migrations were found during this seasonal increase both qualitatively and in a spectral analysis. Concurrently with zooplankton increases, wind forcing produced a deepening of the pycnocline. Zooplankton abundance peaked in the fjord when the pycnocline depth deepened due to wind forcing and throughout the entire spring season, indicating that mixing conditions could favor secondary production. These results were corroborated by the 2014 data, which indicate that weather events in the region impact both fjord physics and ecology.

Most of the atolls found worldwide are under microtidal regimes, and their circulation mechanisms are widely documented and well known. Here, we describe the flushing mechanisms of a small-sized mesotidal atoll, based on water-level, wave and current data obtained during two different periods (total of 60 d). Rocas is the only atoll in the South Atlantic Ocean and is built primarily of coralline algae. Two reef passages connect the atoll lagoon to the ocean. Synchronous current profilers were deployed at the two reef passages, one inside and one outside the atoll, to characterize the influence of tides and waves on the circulation. Results showed that wind waves drove a setup on the exposed side of the atoll and that currents were predominately downwind, causing outflow at both reef passages. Waves breaking on the windward side supplied water to the atoll causing the lagoon water level to rise above ocean water level, driving the outflow. However, unlike microtidal atolls, at Rocas Atoll the water level drops significantly below the reef rim during low tides. This causes the reef rim to act as a barrier to water pumping into the lagoon by waves, resulting in periodic activation of the wave pumping mechanism throughout a tidal cycle. As result, inflow occurs in the wider passage during 27% of each tidal cycle, starting at low tides and reversing direction during mid-flood tide when the water level exceeded approximately 1.6 m (while overtopping the atoll’s rim). Our findings show that tides play a direct role in driving circulation on a mesotidal atoll, not only by modulating wave setup but also by determining the duration of wave pumping into the lagoon.

Dreissena spp. are aggressive invaders of many waterbodies worldwide. However, the accurate assessment of their spatial distribution in large rivers is difficult using traditional sampling techniques such as Ponar grabs or SCUBA diving. The aim of this study was to use sonar technologies and underwater imagery (videos, still images) in tandem with traditional Ponar sampling to predict Dreissena presence, and produce a habitat suitability map to enhance our understanding of its spatial distribution in the lower Niagara River, New York, USA. Geo-referenced maps of environmental variables were generated using three sonar technologies: side scan sonar, multibeam sonar, and an Acoustic Doppler Current Profiler. Dreissena presence/absence was determined at 102 sites along a 10 km stretch using Ponar grabs supplemented by an underwater imagery. Substrate and near-bottom flow were the most important variables affecting Dreissena distribution. Habitats with coarse substrate and near-bottom flow of 0.6–0.80 m/s were predicted to be most often occupied. The habitat suitability model indicates that almost 90% of the stream bed in the river can be considered highly- or moderately suitable habitat. Our results demonstrate that supplementing traditional sampling with sonar technologies and underwater imagery can greatly improve Dreissena distribution assessment at the ecosystem scale.

Gallegos, G.; Marino-Tapia, I., and Valle-Levinson, A., 2016. Effects of gravity waves on turbulence and processes that contribute to mixing at a submarine groundwater discharge. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 856–860. Coconut Creek (Florida), ISSN 0749-0208. Submarine ground water discharges (SGD) around the coasts of the Yucatan Peninsula are very common due to the karstic origin of the rocks, and the abundant rain. These discharges of brackish water into the coastal sea are strong enough to alter the thermohaline conditions, they can be preferential routes for salt intrusion, and also represent an important input of nutrients and pollutants. The mixing on these SGDs is a spontaneous and turbulent process, and its study is important for the understanding of dispersion of materials in regions influenced by these features...

Simultaneous time series of current velocity profiles are used to characterize flow structures over intermediate-depth coral ecosystems in the eastern Gulf of Mexico. Understanding of temporal variability and spatial coherence in flow is necessary to establish connectivity among these ecosystems. Time series were collected at Pulley Ridge (the westernmost site), Northern Dry Tortugas, and Southern Dry Tortugas. Overlapping data spanned the period from March 22, 2013 to June 20, 2015. The strongest currents were approximately 1 m s-1 southeastward at Pulley Ridge. Subtidal velocities from the three sites were decomposed into real-vector, concatenated empirical orthogonal functions (EOFs). Results from EOFs indicated that Mode 1, which explained 63% of the subtidal variance, was roughly in the same direction at each of the three sites. Mode 1 directionality indicated potential interconnectivity between Pulley Ridge and Southern Dry Tortugas, and between Northern Dry Tortugas and Pulley Ridge. Mode 1 also suggested limited to no connectivity between the two Dry Tortugas sites as the flows over the two sites were parallel. Mode 2 explained close to 24% of the variance and showed incoherence among the three sites. Wavelet analysis of EOF coefficients indicated dominance of >1 week variability in this region. Flow variability may be associated with wind forcing and Loop Current variability as confirmed by satellite altimetry. Wind forcing caused part of the intra-monthly ( 1 month) periods. The relationship was more robust, but inverse, when comparing sea level off the northwestern coast of Cuba to the Mode 1 of the currents. These results characterize physical connectivity among South Florida coral ecosystems and have biophysical implications for coral fish populations.

Serrano, M.A.; Diez-Minguito, M.; Valle-Levinson, A., and Ortega-Sanchez, M., 2020. Circulation in a short, microtidal submarine canyon in the Alboran Sea. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1531–1535. Coconut Creek (Florida), ISSN 0749-0208.This study analyzes the circulation of a short, microtidal submarine canyon from observations and an analytical model. The Jolucar submarine canyon is located near the Carchuna beach (Granada, southern Spain) in the northern continental shelf of the Alboran Sea. Observations were analyzed with harmonic and spectral analyses techniques. Observations showed two layers flowing in opposite directions: down-canyon in the bottom layer and up-canyon in the upper layer. This suggest that the canyon might flush out dense materials form the nearshore. Moevoer, observed currents were mainly driven by tidal (10%) and, more significantly, by atmospheric forcing, i.e., by wind stress and local atmospheric pressure gradients, as shown by cross-spectral analysis. In order to explore the dynamics associated with these results, a classical analytical solution of wind-induced current profile in a non-homogeneous water column was extended to include the influence of pressure gradients. This result demonstrated that the circulation in Jolucar canyon could be influenced by atmospheric pressure gradients.

Estimates of turbulence properties with Acoustic Doppler Current Profiler (ADCP) measurements can be muddled by the influence of wave orbital velocities. Previous methods&mdash, Variance Fit, Vertical Adaptive Filtering (VAF), and Cospectra Fit (CF)&mdash, have tried to eliminate wave-induced contamination. However, those methods may not perform well in relatively energetic surface gravity wave or internal wave conditions. The Harmonic Analysis (HA) method proposed here uses power spectral density to identify waves and least squares fits to reconstruct the identified wave signals in current velocity measurements. Then, those reconstructed wave signals are eliminated from the original measurements. Datasets from the northeastern Gulf of Mexico and Cape Canaveral, Florida, are used to test this approach and compare it with the VAF method. Reynolds stress estimates from the HA method agree with the VAF method in the lower half of the water column because wave energy decays with depth. The HA method performs better than the VAF method near the surface during pulses of increased surface gravity wave energy.

Analysis of 19-year-long tidal gauge records along the US East Coast has revealed the appearance of semidiurnal perturbations to storm surges in the South Atlantic Bight. A total of 85 events with semidiurnal-surge amplitudes higher than 20% of the astronomic tidal amplitude and durations longer than two days were identified. These semidiurnal surge events were triggered by the passage of tropical storms and cold fronts. As a consequence of the storm-induced forcing, observed tides were delayed and partially damped with respect to the predictions. Such delay and damping resulted in a semidiurnal signal on the surge. Parallel-to-shore winds in the shelf region between Cape Hatteras and the South Atlantic Bight were highly correlated with the generation of the semidiurnal perturbations. Increased bottom friction combined with Coriolis acceleration, resulting from enhanced wind-driven alongshore currents, are proposed to be the primary factors delaying and attenuating astronomic tides.

Time series of horizontal velocities, echo intensity, wind velocity, and atmospheric pressure were collected for ∼200 days in a Patagonian fjord to explore pycnocline motions produced by the Southern Hemisphere's baroclinic annular mode (BAM). The BAM variability occurs between 20 and 30 days and is associated with fluctuations in atmospheric kinetic energy and in turbulent fluxes of heat. Spectra of horizontal velocities and normalized echo intensity in the fjord's water showed highest energy between 25 and 30 days. This was explained by sustained westerly winds associated with extreme low-pressure systems (∼900 hPa) that had periodicity related to the BAM. Wind forcing produced >40 cm s−1 along-channel and cross-channel currents in the surface layer, which in turn created a wind-induced setup toward the head of the fjord. The setup was accompanied by a deepening of the pycnocline (from 5 to 15 m depth) with ∼25 to 30 day periodicity, as derived from the normalized echo intensity. The dominant empirical orthogonal function mode of the normalized echo intensity profiles explained 70.8% of the variance and also exhibited a ∼25–30 day periodicity. Further, a wavelet and spectral analysis of 10 years of atmospheric pressure indicated peaks between 25 and 30 days each year, indicating that the BAM consistently influences weather patterns in Chilean Patagonia. This is the first documented case of baroclinic annular variability in a specific region of the Southern Hemisphere, and of its effects on fjord systems.

Observations of underway velocity profiles during complete spring and neap tidal cycles were used to determine whether the spatial structures of tidal and subtidal flows at a tidal inlet in a multiple-inlet embayment are consistent with those observed at single-inlet embayments. Measurements were obtained at the Otzumer Balje, one of the multiple inlets among the East Frisian Islands of the Wadden Sea. The 1.5 km-wide inlet displayed a bathymetric profile consisting of a channel ∼15 m deep flanked by

A combination of observations and analytical solutions was used to determine the modifications caused by wind forcing on the residual or nontidal circulation in an ebb-tidal delta. Observations were obtained in the lower Arcachon Lagoon, southwestern France. The basic nontidal circulation was established with acoustic Doppler current profilers (ADCPs) that were (i) moored in the delta's two deepest channels, and (ii) towed along a cross-lagoon transect. The bathymetry of the lower lagoon, or ebb-tidal delta, featured two channels: North Pass (>9 m) and South Pass (>20 m). The basic nontidal circulation consisted of mostly inflow with weak surface outflow in the South Pass, and laterally sheared bidirectional flow, dominated by outflow, in the North Pass. Analytical solutions and comparison of observed dynamical terms suggested that, in addition to the conventionally accepted influence of tidal nonlinearities, density gradients contributed to the basic nontidal circulation in the lagoon. Observations also indicated that wind forcing altered the basic circulation by driving simultaneous upwind flows in both passes. This response was supported by an analytical solution to wind-driven flows over the bathymetry of the transect sampled. The response to seaward winds was to enhance inflow in South Pass and reduce outflow in North Pass. Landward winds caused diminished inflow in South Pass and increased outflow in North Pass.

Time series of acoustic backscatter and vertical velocity profiles were obtained at three sites along a Chilean fjord with the purpose of determining dominant structures of vertical migrations of the sound scattering layer. Ancillary data obtained with stratified net samples indicated that the sound scattering layer may have been dominated by euphausiids and decapods. Therefore, distributions of acoustic backscatter anomalies and vertical velocities were attributed to vertical migrations of predominantly these organisms. Migration patterns were dominated by twilight excursions in which organisms swam toward the water surface at sunset, spent 100 m). This migration strategy can also be termed ‘semidiel migration’ as two double excursions were linked to light levels. The reasons for this twilight migration remain uncertain. But it is possible that the up and down motion around sunset was related to predation avoidance, hunger–satiation state, ontogeny, seaward transport evasion, or reaction to the environmental shock from the pycnocline, or a combination of all or some of them. In contrast, the sunrise double excursion was probably linked to feeding requirements by organisms that need to spend the day at great depth with no food available. This study demonstrated the existence of semidiel patterns throughout the fjord and through prolonged periods. In addition, identification of this pattern by acoustic backscatter was complemented by direct vertical velocity measurements. It is proposed that twilight vertical migration is a common strategy in Chilean fjords.

Year-long time series of water level are analyzed at five locations along the St. Johns River Estuary, Florida, to investigate propagation of subtidal pulses. Hilbert-transformed Empirical Orthogonal Functions (HEOFs) are obtained after a dominant seasonal signal is extracted from the data. These functions provide information on spatial structure and propagation phase of subtidal water level pulses. The first HEOF mode explains 96% of the subtidal variability and features an unusual spatial structure: amplitude attenuation (averaging 1 mm/km) to 55 km upstream, slight amplification (0.16 mm/km) over the middle 70 km, and attenuation (2.3 mm/km) over the final 18 km of the estuary. The phase suggests a shift from progressive to quasi-standing wave behavior at 55 km from the estuary mouth. Additionally, local minima in the phase suggest two sources of subtidal forcing: the coastal ocean and the upstream end. An analytical model describing the evolution of long waves through a channel with frictional damping is fit to the amplitude of HEOF mode 1. Solutions are obtained as a function of two parameters: the nondimensional length of the basin, κ, and the nondimensional frictional depth, δ. Values of κ between 0.55 and 0.67 and δ between 1.45 and 1.7 provide the best fit with the HEOF results (1% error or less). These values indicate a highly frictional environment in which the average subtidal wavelength is 10 times the basin length. Subtidal pulses in this estuary, therefore, behave as damped waves that can be represented with idealized models.

The dynamics associated with lateral circulation in a tidally driven estuarine channel is analyzed on the basis of streamwise vorticity. Without rotational effects, differential advection and diffusive boundary mixing produce two counterrotating vortices (in the cross-channel section) whose strength and sense of circulation may change during a tidal cycle. The streamwise vorticity equation is determined by a balance between baroclinic forcing and turbulent diffusion, which explains the flood–ebb asymmetry of the lateral circulation. Analysis of the lateral salinity gradient shows that differential advection is the main driver of lateral flows, but boundary mixing can also be an important contributor in stratified estuaries. The strength of lateral circulation decreases with increasing stratification. With rotational effects, the lateral Ekman forcing in the bottom boundary layer drives a one-cell lateral circulation that switches its sense of rotation over the tidal cycle. The vorticity budget analysis reveals a three-way balance among the tilting of planetary vorticity by the vertical shear in the along-channel current, baroclinic forcing, and turbulent diffusion. The structure and magnitude of the lateral circulation change with the width of the estuary, expressed nondimensionally as the Kelvin number Ke. This lateral circulation features two counterrotating vortices in narrow estuaries, one vortex filling up the entire cross section in estuaries of intermediate widths and one vortex confined to the left side (looking into the estuary) in wide estuaries. The magnitude of the streamwise vorticity increases rapidly with Ke, reaches a maximum at , and decreases slightly in wide estuaries subject to strong rotational control.

Hurricane Irma impacted the entire Florida peninsula in September 2017. The combination of Irma's strength, size, and track provided a unique opportunity to study hurricane effects on storm surge on both sides of a peninsula. Storm surge characteristics on the west coast of Florida were markedly different from those on the east coast. On the west coast, the maximum storm surge was 1.6 m at Naples, which was attributed to onshore winds and an atmospheric pressure of 970 hPa. A stunning negative surge of −2.7 m appeared at Cedar Key, in the peninsula's northwestern quarter, after ~10 h of oblique offshore and divergent winds. On the east coast, the maximum surge was 2.4 m at Fernandina Beach, where wind velocity displayed horizontal convergence. A revealing finding of this investigation was that wind divergence is an essential component for predicting storm surge.

[1] Application of recent geometric tools for Lagrangian coherent structures (LCS) shows that material attraction in geostrophic velocities derived from altimetry data imposed an important constraint to the motion of drifters from the Grand Lagrangian Deployment (GLAD) in the Gulf of Mexico. This material attraction is largely transparent to traditional Eulerian analysis. Attracting LCS acted as approximate centerpieces for mesoscale patterns formed by the drifters. Persistently attracting LCS cores emerged 1 week before the development of a filament resembling the “tiger tail” of the Deepwater Horizon oil slick, thereby anticipating its formation. Our results suggest that the mesoscale circulation plays a significant role in shaping near-surface transport in the Gulf of Mexico.

[1] Hurricane Sandy drove storm surges throughout the eastern seaboard of the United States, from Miami to Maine, at the end of October 2012. The surge was particularly high (>3 m) in coastal New York. In the southeastern United States, the surge was

International audience; Time series of current velocity profiles and thermistor chains were obtained throughout a cross-bay transect for ~90 days for the purpose of comparing observed wind-driven stratified flows to theory. This study concentrates on the synoptic scale wind and its influence on the bay’s circulation. The maximum water column stratification was 3 – 4 °C/m throughout the deployment and influenced wind-driven flows. Low-pass filtered flows showed more complicated structures than those expected from theory: a depth-dependent recirculating structure with the along-bay flow over one half of the transect moving in opposite direction to the other half. Analysis of complex empirical orthogonal functions indicated that the first six modes explained 80 % of the flow variability. Therefore, there was no predominantly energetic mode of variability. All modesexhibited a rich spatial structure with vertical and lateral variations. For all modes there was vertically sheared bidirectional flow, as expected from theory, with the largest eigenvector (mode value) asymmetrically influenced by Earth’s rotation and advection of momentum.