Ecological Implications of Hydrography and Circulation to the Flower Garden Banks, Northwest Gulf of Mexico

A synthesis of historic and new physical oceanographic observations on the Louisiana-Texas shelf helps change the circulation paradigm around the Flower Garden Banks. The location of these banks near the shelf edge shields them from the direct influence of the Mississippi and Atchafalaya Rivers and summer hypoxic episodes but places them under direct influence of deepwater physical processes. These deepwater processes control temperature and salinity within ranges that are adequate for coral growth; however, summer temperatures can exceed thermal tolerance limits as evidenced by coral bleaching episodes. Currents near the Banks have longshore and significant offshore components. Loop Current (LC) rings and companion eddies (anticyclones and cyclones) with spatial scales of 30-150 km and residence times ~ 6 mo over the slope are the main driving force of shelf edge currents. This active eddy field induces significant and frequent cross-shelf water exchanges with the deep Gulf, which help regulate temperature, salinity, and larvae dispersal. The eddies also induce oxygen and nutrient enrichments near the mixed layer by sinking and rising water parcels that can help the reef biota. Four links between the Flower Garden Banks and the rest of the Gulf of Mexico are identified: the shelf edge current, LC rings and associated eddies, the mean westward surface wind drift in the Gulf, and alongshelf edge intrusions from the northeastern Gulf of Mexico. The coral reefs of the Flower Garden Banks can function as repositories and sources of reef biota

Travel Times of Passive Drifters from the Western Caribbean to the Gulf of Mexico and Florida-Bahamas

Travel times of passive drifters along five predetermined routes connecting coral reefs in the western Caribbean with reefs in the Gulf of Mexico and FloridaBahamas are provided. Mean surface velocities used to estimate time were derived from ship drifts and from satellite-tracked drifters. Estimated times include 55-135 d between Belize and the Flower Garden Banks, 26-42 d between Belize/Yucatan and Florida-Bahamas, and 31 d from Campeche to Vera Cruz. These results agree with the time of waterborne pathogen arrival at the Flower Garden Banks from Belize and an oil slick reaching Texas from Campeche

Slope and Roughness Statistics of the Northern Gulf of Mexico Seafloor With Some Oceanographic Implications

We analyzed 11 cross-slope and six along-slope bathymetric profiles over the continental slope of the northern Gulf of Mexico using statistical and time series techniques. Linear regressions account for over 93% of the water depth variability in nine north-south profiles; the remaining profiles follow quadratic polynomials accounting for over 92% of the variability. Seafloor gradients from the linear fits are generally ≤1°, but local gradients can reach ≅16° near the Sigsbee Escarpment (SE), which is smaller than previously documented. Seafloor roughness elements reach 13-300 m, with most \u3c100m. Such rough bottoms could affect waves with wavelengths of tens of kilometers but not waves of hundreds of kilometers. Water depth power spectra are red (having the most energy at scales ≤10 km) and exhibit a k-2 dependence. Power spectra of short-scale gradients are near constant at scales \u3e0.02 cpkm, implying a white noise process, and overall, these spectra exhibit an exponential dependence. Oceanographically, the slopes are large enough for topographic β-effects to dominate over the planetary β-effect, which allows approximating the topographic Rossby waves (TRWs) dispersion in terms of the Brunt-Vaisala frequency and bottom gradients. The steep SE can sustain minimum periods of ~18 d, which agrees with observed periods. Bottom trapping caused by stratification should be effective only for short waves, but observations suggest that bottom trapping is independent of wavelength. This discrepancy can be explained by the fact that the Gulf of Mexico can be approximated as a two-layer ocean, and TRWs are bottom trapped regardless of wavelength. The critical frequency and slope show that only diurnal and inertial frequencies (at this latitude) could be inducing strong vertical mixing on the study area. The initial conjecture that cyclonic eddies with diameters of 40-150 km are generated by flow-topography interaction was not upheld because the resonance conditions are not met. Finally, the analysis reveals that fluids inside basins cannot escape

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Reef front wave energy

In summary, waves transiting the sloping reef front experience decreasing water depths and increasingly rough bottom (high bottom friction/drag coefficients) that cause refraction, shoaling, and energy dissipation (bottom friction and wave breaking). Net wave energy reductions of 72–99% have been estimated from measured wave heights over many reefs that maintain a wave height gradient across the reef front. The resulting reef front wave field provides energy that drives or supports biological and chemical processes of the reef ecosystem, geological and morphological processes over and in the reef, and a wave-driven flow that connects the reef front to the backreef lagoon. Efficient dissipation of wave energy by coral reefs provides some measure of protection against large hurricane waves and tsunamis to backreef lagoons and shores

Lagoon circulation

Coral reef lagoons span a wide spectrum from small nearly closed to large and open lagoons in atolls. Water circulation in these lagoons results from the strength and duration of driving forces (e.g., wind speed and direction, wave-swell height and direction, tides, major currents, and salinity and water temperature variations) and their interaction with the morphology and geometry of the lagoon. In small nearly closed lagoons, currents are directed nearly parallel to the coastline because of the morphological and geometric constraints under the action of waves, tides, and winds. As the size and openness of the lagoon increases, winds and tides become the dominant forces of water circulation. In large lagoons of atolls, winds and tides are the primary forces of circulation assisted by the wave driven across the reef flux. However, because these lagoons are much deeper, water stratification becomes relevant and twolayer flows are common

Proceedings: USA-Mexico Workshop on the Deepwater Physical Oceanography of the Gulf of Mexico

A review of the understanding of the deepwater physical oceanography of the Gulf of Mexico

Biologic and geologic responses to physical processes: examples from modern reef systems of the Caribbean-Atlantic region

Coral reefs and associated depositional environments of the Caribbean-Atlantic region have characteristics that reflect control by physical processes, both oceanic and atmospheric. Wave direction and wave power help determine sites for productive reef development and shape reef morphology as well as community structure. Spur and groove orientations reflect changes in direction of waves as they refract across a reef-dominated shelf. Abrupt topography of reef-dominated shelf margins interacts with tidally modulated flows to create an energetic and productive deep reef environment which is buffered from the modifying effects of forceful wave action.Shallow wave-reef interactions involve dissipative effects of wave breaking, turbulence, and friction, resulting in measured wave energy transformations ranging from 72 to 97% depending on reef configuration and water depth. Dissipative processes produce strong reef-normal surge currents that transport sediment lagoonward, drive backreef lagoon circulation, and influence fluid flow and diagenesis within the reef. The intensity of these processes is modulated at the tidal frequency. Other long period waves (infragravity) are important agents of mass transport of water and fine sediment. Low speed, long duration currents forced by long waves are potentially important for transporting larvae as well as fine sediment out of a given reef-lagoon system.Ocean-scale currents impinging on steep island and continental margin topography may cause reef-limiting upwelling and nutrient loading. The Caribbean Current upwells on the Nicaragua shelf and carbonate platforms of the Nicaraguan Rise. High trophic resources favor algal rather than coral communities and large (20–30 m relief) Halimeda biotherms occupy niches normally reserved for coral reefs.Thermodynamic air-sea interactions (heat, moisture and momentum flux) regulate the physical properties of reef lagoon and bank top waters. In extra-tropical reef settings (e.g. Bermuda, Florida, Bahamas and Arabian Gulf) cold air outbreaks cause precipitous drops in bank water temperatures and significant increases in bank water salinity and suspended sediment load. Water temperatures are routinely forced below the limit for survival of reef corals and many species of calcareous green algae. Associated increases in the density of shallow waters produce a disequilibrium with surface waters of the adjacent ocean favouring shelf transport to deep water sites of reef development and beyond

Wave transformations across a caribbean fringing-barrier Coral Reef

Wave measurements during three experiments at Tague Reef, St. Croix (U.S.V.I.) in April 1987 showed a net energy decrease across the reef profile of 65-71% between the forereef and crest, wave propagation to the backreef increased energy reduction to 78-88%. Tidally induced water depth changes (range of 0.3 m) increased wave energy dissipation by 15% between forereef and crest and 20% between forereef and backreef. Significant wave heights throughout the experiment were low (\u3c 0.5 m) and exhibited a tidal modulation in the backreef or lagoon. Wave transmission over the reef averaged 0.46 and modulated by the tide (0.32 at low tide vs 0.62 at high tide). The spectral time-delay model applied to analyzed wave transformations across the reef produced attenuation coefficients that averaged 0.62 between 0.05 and 0.1 cps (20-10 s) and afterwards oscillate between 0.22 and 0.35. For waves between the forereef and backreef, the attenuation coefficients from the time-delay model decay exponentially between 0.05 and 0.1 cps, afterwards they oscillate between 0,13 and 0.2. The steady wave-energy model with bottom friction, essentially form drag, and wave breaking dissipation yield wave heights modulated by the tides and errors of \u3c 19% in the crest and \u3e 20% at the backreef. The model revealed that while frictional and wave-breaking dissipation are equally important, frictional dissipation is greater