Jorge Capella

Nitrous oxide fluxes in Caribbean and tropical Atlantic waters : evidence for near surface production

Abstract Nitrous oxide is recognized as a potent greenhouse gas and an intermediate in the destruction of stratospheric ozone, as well as a source of tropospheric ozone. We present data on the vertical and latitudinal distribution of nitrous oxide and estimation of fluxes across the sea–air and thermocline interfaces in tropical ocean waters north and south of Puerto Rico. Air–sea nitrous oxide fluxes computed from data collected during April 1995 and June 1996 are comparable to rates reported for marginal seas. However, close to 70% of the sea–air flux is not accounted for by cross-thermocline flux. Although the effect of physical processes cannot be ruled out as a factor in this differential at all locations, our observations provide evidence for active nitrous oxide production in near-surface tropical waters.

Cyclonic eddy entrains Orinoco River Plume in eastern Caribbean

“Mesoscale” eddies are large whirlpools in the ocean with diameters of hundreds of kilometers. Their influence can extend to depths of 1000 m or greater. Oceanographers are only now beginning to document the prevalence, extent, and influence of such features in the world ocean. The availability of third-generation ocean color imagery from the Moderate Resolution Imaging Spectroradiometer-MODIS sensors aboard NASAs AQUA and TERRA platforms, and support for direct observation at sea, have now allowed characterization of such an eddy interacting with the Orinoco River plume (ORP) while traversing the eastern Caribbean basin.

Development of an Operational Nearshore Wave Forecast System for Puerto Rico and the U.S. Virgin Islands

Abstract Anselmi-Molina, C.M.; Canals, M.; Morell, J.; Gonzalez, J.; Capella, J., and Mercado, A, 2012. Development of an operational nearshore wave forecast system for Puerto Rico and the U.S. Virgin Islands. An assessment of coastal information needs in Puerto Rico and the U.S. Virgin Islands identified real-time wave data and improved wave forecasts as essential for supporting nearshore operations in the region. After deployment of operational wave-measuring buoys off the north, south, east, and west coasts of the Puerto Rico–Virgin Islands archipelago, the Simulating WAves Nearshore (SWAN) model was implemented for the region. The main purpose of its implementation is to provide for data needs in areas not well represented by the buoys as well as for filling the nearshore gap not addressed by the operational National Oceanic and Atmospheric Administration (NOAA) Multigrid WAVEWATCH III (NMWWIII) model forecast. The model consists of a nesting between WWIII and SWAN where oceanic boundary conditions in the form of two-dimensional wave spectra are supplied by the NMWWIII model. In this study we present results from two model-validation experiments under varying physical-forcing scenarios, one in which swell waves dominate (Rincón) and one in which wind swell dominates (Ponce). The results show good agreement between the observed and the modeled wave field for the Rincón domain, on Puerto Ricos northwest coast and facing the Atlantic Ocean, which indicates that appropriate boundary conditions are being obtained from NMWWIII and propagated correctly by SWAN into nearshore areas. Results for the Ponce domain, in Puerto Ricos southern coast and facing the Caribbean Sea, highlight the need for more accurate high-resolution wind products to properly resolve the wind-driven wave field dominating this area.

Optimizing and validating high-frequency radar surface current measurements in the Mona Passage

Mapping of the ocean surface velocity field of the eastern Mona Passage is important due to the fact that the Passage is a major shipping lane to the Panama Canal, as well as a key route for illegal traffic into the United States. As such, two high-frequency radar (HFR) stations have been emplaced along the west coast of Puerto Rico to allow such mapping and to explore its performance in vessel detection and tracking. Coverage of the south-eastern quadrant of the Passage is provided, extending west to Mona Island and north to Rincon. Results were posted online hourly in near real-time, and to optimize these results, antenna beam patterns were measured twice and corrections applied to the resulting radial returns. Validation measurements were undertaken in order to assess the basic capability of the Mona Passage HFR array to measure surface currents in this tropical environment, including repeated deployment of Lagrangian drifters, as well as an acoustic Doppler current profiler, and compared with modeled tidal currents. The experimental measures demonstrated good agreement to both in situ and modeled data, thus lending confidence to the area-wide surface current maps generated by this system. Demonstrating that these are in large part the product of the surrounding environment, repeated measurements showed limited temporal variability of antenna distortion patterns. Comparing experimental Lagrangian trajectories and a numerical particle tracking algorithm showed mixed results, achieving better agreement during periods of low intrahour variability in current direction than during periods of rapid tidal reversal.

Characterization of mesoscale eddies and detection of submesoscale eddies derived from satellite imagery and HF radar off the coast of southwestern Puerto Rico

Coherent sub-mesoscale features such as spiral eddies are known to be ubiquitous in the worlds oceans. Yet, due to their complex geometry, they are often difficult to characterize. Sub-mesoscale ocean dynamics with characteristic dimensions on the order of kilometers have been found to play a major role in upper ocean stirring and mixing. Manifestations of these structures all around the Caribbean Coastal Ocean Observing System (CariCOOS) region have been found to influence coastal and oceanic waters impacting upper ocean hydrodynamics and biogeochemistry. CariCOOS modeling efforts in the region have yet to produce reliable forecasts of near coastal ocean dynamics. Owing to the growing demand for coastal ocean models yielding accurate forecast, CariCOOS has proposed the operational deployment of a 1/100 degree Regional Ocean Modelling System (ROMS) nested in the 1/36 degree resolution Navy Coastal Ocean Model (AMSEAS) which itself is nested in the Hybrid Coordinate Ocean Model (HYCOM), a global 1/12 degree data-assimilative hybrid isopycnal-sigma-pressure coordinates forecast system. Although the progression has been consistent, results urge the identification of possible skill performance constraints and phenomenological limitations. An inward approach has been adopted to assess the output of parent models versus observations from satellites, drifters, gliders, sea level measurements, buoys, and HF radars. Part of the adopted approach focuses on the characterization and daily-based detection of sub-mesoscale ocean dynamic features. CariCOOS observational assets and satellite imagery brings forth the ability to characterize quasi-permanent (or periodical) phenomena close to the coast. Thanks to the recent expansion of the CariCOOS High-Frequency (HF) radar network consisting of two long range (5 MHz) antennas on the southwestern coast of Puerto Rico, unprecedented spatial and temporal coverage will be available for this two-part study. For the first part, historical satellite altimetry, as well as other discrete observations, will be used to characterize the quasi-geostrophic mesoscale eddy signatures near the southwestern coast of Puerto Rico. On the second part, satellite imagery and HF radar capabilities to capture sub-mesoscale eddy phenomena will be assessed with the objective of implementing coherent structure detection algorithm based on a vector geometry method. A comparison between detected sub-mesoscale eddies with HF radars and available operational models (AMSEAS & HYCOM) will be qualitatively assessed.