Analysis of Vertical Velocities Development through High-resolution Simulation and Glider Observations in the Alboran Sea

2021 ◽  
Author(s):  
Maximo Garcia-Jove ◽  
Baptiste Mourre ◽  
Nikolaos Zarokanellos ◽  
Pierre F. J. Lermusiaux ◽  
Daniel L. Rudnick ◽  
...  
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
Naval Research ◽  
Alboran Sea ◽  
Surface Ocean ◽  
Office Of Naval Research ◽  
Research Initiative ◽  
Spatio Temporal ◽  
Alborán Sea ◽  
Resolution Simulation

<p>Vertical velocities associated with meso- and submeso-scale structures generate important vertical fluxes of carbon and other biogeochemical tracers from the surface layer to depths below the mixed layer. Vertical velocities are very weak and characterized by small scales which make them difficult to measure. The project entitled Coherent Lagrangian Pathways from the Surface Ocean to Interior (CALYPSO, Office of Naval Research initiative) addresses the challenge of observing, understanding, and predicting the vertical velocities and three-dimensional pathways on subduction processes in the frontal regions of the Alboran Sea. Within the framework of the CALYPSO project, we analysed the processes that give rise to vertical velocities in the Western Alboran Gyre Front (WAGF) and Eastern Alboran Gyre Front (EAGF). The periods of frontal intensification were analyzed in the perspective of the frontogenesis, instabilities, non-linear Ekman effects, and filamentogenesis using multi-platform in-situ observations and a high-resolution simulation in spring 2018. The spatio-temporal characteristics of the WAGF indicate a wider, deeper, and longer-lasting front than the EAGF. The WAGF intensification and vertical velocities development are explained through i) frontogenesis, ii) conditions for symmetric and ageostrophic baroclinic instabilities generation, and iii) nonlinear Ekman effects. These mechanisms participate to generate and strengthen an ageostrophic secondary circulation responsible for vertical velocities intensification in the front. In the case of the EAGF, the intensification and vertical velocities development are explained by filamentogenesis in both the model and glider observations. The EAGF intensification is characterized by a sharp and outcropping density gradient at the center of the filament, where two asymmetrical ageostrophic cells develop across the front with narrow upwelling region in the middle.</p>

scholarly journals Rapid climatic variability in the west Mediterranean during the last 25 000 years from high resolution pollen data

2009 ◽  
Vol 5 (3) ◽  
pp. 503-521 ◽  
Author(s):  
N. Combourieu Nebout ◽  
O. Peyron ◽  
I. Dormoy ◽  
S. Desprat ◽  
C. Beaudouin ◽  
...  
Keyword(s):  
High Resolution ◽  
North Atlantic ◽  
Climate Reconstruction ◽  
Mediterranean Vegetation ◽  
Pollen Record ◽  
Alboran Sea ◽  
Climatic Fluctuations ◽  
The Holocene ◽  
The Mediterranean ◽  
Alborán Sea

Abstract. High-temporal resolution pollen record from the Alboran Sea ODP Site 976, pollen-based quantitative climate reconstruction and biomisation show that changes of Mediterranean vegetation have been clearly modulated by short and long term variability during the last 25 000 years. The reliability of the quantitative climate reconstruction from marine pollen spectra has been tested using 22 marine core-top samples from the Mediterranean. The ODP Site 976 pollen record and climatic reconstruction confirm that Mediterranean environments have a rapid response to the climatic fluctuations during the last Termination. The western Mediterranean vegetation response appears nearly synchronous with North Atlantic variability during the last deglaciation as well as during the Holocene. High-resolution analyses of the ODP Site 976 pollen record show a cooling trend during the Bölling/Allerød period. In addition, this period is marked by two warm episodes bracketing a cooling event that represent the Bölling-Older Dryas-Allerød succession. During the Holocene, recurrent declines of the forest cover over the Alboran Sea borderlands indicate climate events that correlate well with several events of increased Mediterranean dryness observed on the continent and with Mediterranean Sea cooling episodes detected by alkenone-based sea surface temperature reconstructions. These events clearly reflect the response of the Mediterranean vegetation to the North Atlantic Holocene cold events.

scholarly journals New insight into 3-D mesoscale eddy properties from CMEMS operational models in the western Mediterranean

Ocean Science ◽  
2019 ◽  
Vol 15 (4) ◽  
pp. 1111-1131 ◽  
Author(s):  
Evan Mason ◽  
Simón Ruiz ◽  
Romain Bourdalle-Badie ◽  
Guillaume Reffray ◽  
Marcos García-Sotillo ◽  
...  
Keyword(s):  
Composite Structures ◽  
Global Analysis ◽  
Rapid Evolution ◽  
Mesoscale Eddy ◽  
Three Dimensional ◽  
Western Mediterranean ◽  
Alboran Sea ◽  
Western Mediterranean Sea ◽  
Common Domain ◽  
Alborán Sea

Abstract. Rapid evolution of operational ocean forecasting systems is driven by advances in numerics and data assimilation schemes, and increase of in situ and satellite observations. The Copernicus Marine Service (CMEMS) is a major provider of operational products that are made available through an online catalogue. The service includes global and regional forecasts in near-real-time and reanalysis modes. Here, we apply an eddy tracker to daily sea surface height (SSH) fields from three such reanalysis products from the CMEMS catalogue, with the objective to evaluate their performance in terms of their eddy properties and three-dimensional composite structures over the 2013–2016 period. The products are (i) the Global Analysis Forecast, (ii) the Mediterranean Analysis Forecast and (iii) the Iberia–Biscay–Ireland Analysis Forecast. The common domain between these reanalyses is the western Mediterranean Sea (WMED) between the Strait of Gibraltar and Sardinia. This is a complex region with strong density gradients, especially in the Alboran Sea in the west where Atlantic and Mediterranean waters compete. Surface eddy property maps over the WMED of eddy radii, amplitudes and nonlinearity are consistent between the models, as well as with gridded altimetric data that serve as a reference. Mean 3-D eddy composites are shown only for three subregions in the Alboran Sea. These are mostly consistent between the models, with minor differences being attributed to details of the respective model configurations. This information can be informative for the ongoing development of these CMEMS operational modeling systems. The mesoscale data provided here may be of interest to CMEMS users and in the future could be a useful addition to a more diverse CMEMS catalogue.

scholarly journals Data set of Arctic AVHRR imagery for the study of leads

1993 ◽  
Vol 17 ◽  
pp. 398-404 ◽  
Author(s):  
Florence Fetterer ◽  
Jeffrey Hawkins
Keyword(s):  
Data Center ◽  
Image Data ◽  
The Arctic ◽  
Naval Research ◽  
Data Set ◽  
Office Of Naval Research ◽  
Research Initiative ◽  
Microwave Imager ◽  
Avhrr Imagery ◽  
Very High

Under the Office of Naval Research-sponsored Arctic Leads Accelerated Research Initiative (ARI), a data set of Advanced Very High Resolution Radiometer (AVHRR) imagery covering the years 1988 through 1992 is being constructed. Relatively cloud-free imagery is selected from image hardcopies. Each image examined is subjectively ranked on the percentage of each sea or seas it covers, and the cloudiness of the image within each sea. The images are then logged in a spreadsheet. From the spreadsheet, about 20 images per month (for the year 1989) are ordered from the National Oceanic and Atmospheric Administration for processing. The image data are calibrated and mapped to one of two grids, which together cover most of the Arctic at 1 km per pixel. Care has been taken to match the grid and the projection to that of Special Sensor Microwave Imager (SSM/I) data distributed by the National Snow and Ice Data Center (NSIDC). The 1989 data set is complete at this time. Presently, data are distributed to the Remote Sensing Working Group of the ARI. NSIDC will distribute the data set to a wider audience at a later date.

scholarly journals Characterization of the submesoscale energy cascade in the Alboran Sea thermocline from spectral analysis of high-resolution MCS data

2016 ◽  
Vol 43 (12) ◽  
pp. 6461-6468 ◽  
Author(s):  
Valenti Sallares ◽  
Jhon F. Mojica ◽  
Berta Biescas ◽  
Dirk Klaeschen ◽  
Eulàlia Gràcia
Keyword(s):  
Spectral Analysis ◽  
High Resolution ◽  
Energy Cascade ◽  
Alboran Sea ◽  
Alborán Sea

Removal of diurnal tidal effects from an ultra‐high‐resolution 3-D marine seismic survey on the continental shelf offshore New Jersey

Geophysics ◽  
1998 ◽  
Vol 63 (3) ◽  
pp. 1036-1040 ◽  
Author(s):  
Eddy C. Luhurbudi ◽  
Jay Pulliam ◽  
James A. Austin ◽  
Steffen Saustrup ◽  
Paul L. Stoffa
Keyword(s):  
New Jersey ◽  
High Resolution ◽  
Single Channel ◽  
Late Quaternary ◽  
Seismic Survey ◽  
Spatial Density ◽  
Naval Research ◽  
Band Pass Filter ◽  
Pass Filter ◽  
Office Of Naval Research

An ultra‐high‐resolution 3-D, single‐channel seismic survey was performed off the coast of New Jersey in 1993 to study the late Quaternary history of sedimentation on the northwest Atlantic continental margin (see Davies et al., 1992) as a part of the Office of Naval Research STRATAFORM initiative (Nittrouer and Kravitz, 1995). Three different sets of profiles were acquired (Figure 1), but only the set with highest spatial density is discussed here. A single ten‐element receiver recorded 300 ms of data for every shot during the survey, which covers a total area of 0.6 km (north‐south) × 7.75 km (east‐west) (see Table 1). The deep‐towed Huntec™ source (deployed at ∼30 m depth) produced frequencies of 500 to 3500 Hz; a band‐pass filter with corner frequencies at 1000 and 3500 Hz was applied during preprocessing.

Doppler Correction of Wave Frequency Spectra Measured by Underway Vessels

2017 ◽  
Vol 34 (2) ◽  
pp. 429-436 ◽  
Author(s):  
C. O. Collins ◽  
B. Blomquist ◽  
O. Persson ◽  
B. Lund ◽  
W. E. Rogers ◽  
...  
Keyword(s):  
Doppler Shift ◽  
Wave Spectrum ◽  
Wave Model ◽  
Practical Method ◽  
Naval Research ◽  
Laser Rangefinder ◽  
Wave Direction ◽  
Frequency Spectra ◽  
Office Of Naval Research ◽  
Research Initiative

Abstract“Sea State and Boundary Layer Physics of the Emerging Arctic Ocean” is an ongoing Departmental Research Initiative sponsored by the Office of Naval Research (http://www.apl.washington.edu/project/project.php?id=arctic_sea_state). The field component took place in the fall of 2015 within the Beaufort and Chukchi Seas and involved the deployment of a number of wave instruments, including a downward-looking Riegl laser rangefinder mounted on the foremast of the R/V Sikuliaq. Although time series measurements on a stationary vessel are thought to be accurate, an underway vessel introduces a Doppler shift to the observed wave spectrum. This Doppler shift is a function of the wavenumber vector and the velocity vector of the vessel. Of all the possible relative angles between wave direction and vessel heading, there are two main scenarios: 1) vessel steaming into waves and 2) vessel steaming with waves. Previous studies have considered only a subset of cases, and all were in scenario 1. This was likely to avoid ambiguities, which arise when the vessel is steaming with waves. This study addresses the ambiguities and analyzes arbitrary cases. In addition, a practical method is provided that is useful in situations when the vessel is changing speed or heading. These methods improved the laser rangefinder estimates of spectral shapes and peak parameters when compared to nearby buoys and a spectral wave model.

Subducting filaments at fronts in the Alboran Sea: Physical, turbulent and biological evidences.

2020 ◽  
Author(s):  
Francesco Marcello Falcieri ◽  
Mathieu Dever ◽  
Mara Freilich ◽  
Annalisa Griffa ◽  
Katrin Schroeder ◽  
...  
Keyword(s):  
Western Mediterranean ◽  
Point Of View ◽  
Surface Mixed Layer ◽  
Alboran Sea ◽  
Vertical Exchange ◽  
Turbulent Dissipation ◽  
Oceanic Fronts ◽  
Dissipation Rates ◽  
Research Initiative ◽  
Alborán Sea

<p>Submesoscale instabilities along oceanic fronts can cause water mass intrusions from the surface mixed layer into the stratified pycnocline. These are important drivers of vertical exchange that have a potentially significant impact on the transfer of physical properties and biological tracers.</p><p>The CALYPSO (Coherent Lagrangian Pathways from the Surface Ocean to Interior) ONR research initiative focuses on observing and understanding coherent vertical pathways by which vertical exchange occurs. The Alboran Sea (located in the south-western Mediterranean, east of Gibraltar) is well known for its strong density fronts and eddies. During a research cruise, onboard <em>R/V Pourquoi Pas? </em>in early April 2019<em>,</em> we found that fronts in this area support the generation of subducting filaments. Several types of observations (using CTD, uCTD, microstructure profiles, drifters and floats) were collected along numerous cross-front transects over a period of two weeks.</p><p>The analysis of the temperature profiles highlighted the presence of several intruding filaments moving along isopycnal surfaces in the proximity of the frontal area. The intrusion signal was also clearly visible in biophysical properties with elevated Chlorophyll-a concentrations, well below the deep chlorophyll maximum, in conjunction with high dissolved oxygen values. From a microstructure point of view, the upper and lower limits of the subducting filaments exhibited high turbulent dissipation rates, with values of O(10<sup>-7</sup>) W/m<sup>2</sup>. These dissipation rates are higher than what is generally observed at such depths and point to enhanced mixing activity at the boundaries of the intrusions even along isopycnal surfaces.</p>

Sign in / Sign up

Export Citation Format

Share Document