ALBERT

Description: The Ocean Color component of the Aerosol Robotic Network (AERONET-OC) has been implemented to support long-term satellite ocean color investigations through cross-site consistent and accurate measurements collected by autonomous radiometer systems deployed on offshore fixed platforms. The ultimate purpose of AERONET-OC is the production of standardized measurements performed at different sites with identical measuring systems and protocols, calibrated using a single reference source and method, and processed with the same code. The AERONET-OC primary data product is the normalized water leaving radiance determined at center-wavelengths of interest for satellite ocean color applications, with an uncertainty lower than 5% in the blue-green spectral regions and higher than 8% in the red. Measurements collected at 6 sites counting the northern Adriatic Sea, the Baltic Proper, the Gulf of Finland, the Persian Gulf, and, the northern and southern margins of the Middle Atlantic Bay, have shown the capability of producing quality assured data over a wide range of bio-optical conditions including Case-2 yellow substance- and sedimentdominated waters. This work briefly introduces network elements like: deployment sites, measurement method, instrument calibration, processing scheme, quality-assurance, uncertainties, data archive and products accessibility. Emphases is given to those elements which underline the network strengths (i.e., mostly standardization of any network element) and its weaknesses (i.e., the use of consolidated, but old-fashioned technology). The work also addresses the application of AERONET-OC data to the validation of primary satellite radiometric products over a variety of complex coastal waters and finally provides elements for the identification of new deployment sites most suitable to support satellite ocean color missions.

Description: Phytoplankton photosynthesis in the sun lit upper layer of the global ocean is the overwhelmingly dominant source of organic matter that fuels marine ecosystems. Phytoplankton contribute roughly half of the global (land and ocean) net primary production (NPP; gross photosynthesis minus plant respiration) and phytoplankton carbon fixation is the primary conduit through which atmospheric CO2 concentrations interact with the ocean s carbon cycle. Phytoplankton productivity depends on the availability of sunlight, macronutrients (e.g., nitrogen, phosphorous), and micronutrients (e.g., iron), and thus is sensitive to climate-driven changes in the delivery of these resources to the euphotic zone

Description: Fixation of organic carbon by phytoplankton is the foundation of nearly all open-ocean ecosystems and a critical part of the global carbon cycle. But quantification and validation of ocean primary productivity at large scale remains a major challenge, due to limited coverage of ship-based measurements and the difficulty of validating diverse measurement techniques. Accurate primary productivity measurements from autonomous platforms would be highly desirable, due to much greater potential coverage. In pursuit of this goal we estimate gross primary productivity over two months in the springtime North Atlantic from an autonomous Lagrangian float using diel cycles of particulate organic carbon derived from optical beam attenuation. We test method precision and accuracy by comparison against entirely independent estimates from a locally parameterized model based on chlorophyll a and light measurements from the same float. During nutrient replete conditions (80% of the study period), we obtain strong relative agreement between the independent methods across an order of magnitude of productivities (r(sq.)=0.97), with slight under-estimation by the diel cycles method (-19+/-5 %). At the end of the diatom bloom, this relative difference increases to -58 % for a six-day period, likely a response to SiO4 limitation, which is not included in the model. In addition, we estimate gross oxygen productivity from O2 diel cycles and find strong correlation with diel cycles-based gross primary productivity over the entire deployment, providing further qualitative support to both methods. Finally, simultaneous estimates of net community productivity, carbon export and particle size suggest that bloom growth is halted by a combination of reduced productivity due to SiO4 limitation and increased export efficiency due to rapid aggregation. After the diatom bloom, high chlorophyll a normalized productivity indicates that low net growth during this period is due to increased heterotrophic respiration and not nutrient limitation. These findings represent a significant advance in the accuracy and completeness of upper ocean carbon cycle measurements from an autonomous platform.

Description: NASA's projects for the Mississippi River Coastal Margin Study include Mississippi River Interdisciplinary Research (MiRIR) and NASA Experimental Program to Stimulate Competitive Research (EPSCoR). These projects, undertaken with the help of Tulane University and the Louisiana Universities Marine Consortium (LUMCON) sampled water in the Gulf of Mexico to measure colored dissolved organic matter (CDOM). This viewgraph presentation contains images of each program's sampling strategy and equipment.

Description: The accurate determination of upper ocean apparent optical properties (AOPs) is essential for the vicarious calibration of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) instrument and the validation of the derived data products. To evaluate the importance of data analysis methods upon derived AOP values, the Second Data Analysis Round Robin (DARR-00) activity was planned during the latter half of 1999 and executed during March 2000. The focus of the study was the intercomparison of several standard AOP parameters: (1) the upwelled radiance immediately below the sea surface, L(sub u)(0(-),lambda); (2) the downward irradiance immediately below the sea surface, E(sub d)(0(-),lambda); (3) the diffuse attenuation coefficients from the upwelling radiance and the downward irradiance profiles, L(sub L)(lambda) and K(sub d)(lambda), respectively; (4) the incident solar irradiance immediately above the sea surface, E(sub d)(0(+),lambda); (5) the remote sensing reflectance, R(sub rs)(lambda); (6) the normalized water-leaving radiance, [L(sub W)(lambda)](sub N); (7) the upward irradiance immediately below the sea surface, E(sub u)(0(-)), which is used with the upwelled radiance to derive the nadir Q-factor immediately below the sea surface, Q(sub n)(0(-),lambda); and (8) ancillary parameters like the solar zenith angle, theta, and the total chlorophyll concentration, C(sub Ta), derived from the optical data through statistical algorithms. In the results reported here, different methodologies from three research groups were applied to an identical set of 40 multispectral casts in order to evaluate the degree to which differences in data analysis methods influence AOP estimation, and whether any general improvements can be made. The overall results of DARR-00 are presented in Chapter 1 and the individual methods used by the three groups and their data processors are presented in Chapters 2-4.

Description: This report presents the Bouee pour l'acquisition de Series Optiques a Long Terme (BOUSSOLE) project, the primary objectives of which are to provide a long-term time series of optical properties in support of a) calibration and validation activities associated with satellite ocean color missions, and b) bio-optical research in oceanic waters. The following are included in the report: 1) an introduction to the rationale for establishing the project; 2) a definition of vicarious calibration and the specific requirements attached to it; 3) the organization of the project and the characteristics of the measurement site--in the northwestern Mediterranean Sea; 4) a qualitative overview of the collected data; 5) details about the buoy that was specifically designed and built for this project; 6) data collection protocols and data processing techniques; 7) a quantitative summary of the collected data, and a discussion of some sample results, including match-up analyses for the currently operational ocean color sensors, namely MERIS, SeaWiFS, and MODIS; and 8) preliminary results of the vicarious radiometric calibration of MERIS, including a tentative uncertainty budget. The results of this match-up analysis allow performance comparisons of various ocean color sensors to be performed, demonstrating the ability of the BOUSSOLE activity, i.e., combining a dedicated platform and commercial-off-the-shelf instrumentation, to provide data qualified to monitor the quality of ocean color products on the long term.

Description: During the passage of a cold front in March 2002, bio-optical properties examined in coastal waters impacted by the Mississippi River indicated westward advective flows and increasing river discharge containing a larger nonalgal particle content contributed significantly to surface optical variability. A comparison of seasonal data from three cruises indicated spectral models of absorption and scattering to be generally consistent with other coastal environments, while their parameterization in terms of chlorophyll a concentration (Chl) showed seasonal variability. The exponential slope of the colored dissolved organic matter (CDOM) averaged 0.0161 plus or minus 0.00054 per nanometer, and for nonalgal absorption it averaged 0.011 per nanometer with deviations from general trends observed due to anomalous water properties. Although the phytoplankton specific absorption coefficients varied over a wide range (0.02 to 0.1 square meters (mg Chl) sup -1)) being higher in offshore surface waters, values of phytoplankton absorption spectra at the SeaWiFS wavebands were highly correlated to modeled values. The normalized scattering spectral shapes and the mean spectrum were in agreement to observations in other coastal waters, while the backscattering ratios were on average lower in phytoplankton dominated surface waters (0.0101 plus or minus 0.002) and higher in near-bottom waters (0.0191 plus or minus 0.0045) with low Chl. Average percent differences in remote sensing reflectance R (sub rs) derived form modeled and in-eater radiometric measurements were highest in the blue wavebands (52%) and at sampling stations with a ore stratified water column. Estimates of Chl and CDOM absorption derived from SeaWiFS images generated using regional empirical algorithms were highly correlated to in situ data.

Description: The Coral Reef Early Warning System (CREWS) is operated by NOAA's Office of Oceanic and Atmospheric Research as part of its Coral Reef Watch program in response to the deteriorating global state of coral reef and related benthic ecosystems. In addition to sea surface temperatures (SSTs), the two most important parameters used by the CREWS network in generating coral reef bleaching alerts are 1) wind speed and direction and 2) photosynthetically available radiation (PAR). NASA remote sensing products that can enhance CREWS in these areas include SST and PAR products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and wind data from the Quick Scatterometer (QuikSCAT). CREWS researchers are also interested in chlorophyll, chromophoric dissolved organic matter (CDOM), and salinity. Chlorophyll and CDOM are directly available as NASA products, while rainfall (an available NASA product) can be used as a proxy for salinity. Other potential NASA inputs include surface reflectance products from MODIS, the Advanced Spaceborne Thermal Emission and Reflection Radiometer, and Landsat. This report also identifies NASA-supported ocean circulation models and products from future satellite missions that might enchance the CREWS DST.

Description: Marsili is a back-arc volcano with a dominant tholeitic petrochemical affinity. This seamount, having an elevation of about 3000 m above the sea floor, an approximate length of 60 km in a NNE-SSW direction and a mean width of 25 km, is the biggest European volcano. The opening of the Marsili basin was related to a sharp acceleration of the roll-back of the Ionian lithosphere subducting below the Southern Tyrrhenian Basin. On the basis of all the geophysical, geological and petrological information knower, Marsili volcano can be considered as being the key needed to understand the dynamics of spreading and back-arc lithosphere formation in this Tyrrhenian sector. However, despite its importance in the Mediterranean geodynamical contest the seismo-volcanic and hydrothermal activity of this seamount remained little known. For this reason in 2006, in the framework of PRO.ME.TH.E.US project (Program of Mediterranean Exploration for Thermal Energy Use), founded by PRAMA s.r.l (Italy) (now Eurobuilding SpA), a multi-disciplinary research was conducted on the Marsili volcano area. In the framework of this project the INGV’s staff placed a broadband OBS/H (Ocean Bottom Seismometer with Hydrophone) on Marsili’s flat top (39° 16,383’ lat. Nord, 14° 23,588’ long. Est.) at a depth of 790 m. For this experiment the OBS/H operated from July 12th to 21st 2006. In only 9 days the submarine seismic station recorded more than 1000 seismo-volcanic and hydrothermal signals. By comparing the signals recorded with typical volcanic seismic activity, we group the recorded signals into: Volcano-Tectonic type B (817 VTB) events, occurrences of High Frequency Tremor (159 HFT) and quasi-monochromatic Short Duration Events (32 SDE). The small-magnitude VT-B swarms, having a frequency band of 2 - 6 Hz and a mean length of about 30 seconds, were almost all recorded during the first 7 days. During the last 2 days, the OBS/H mainly recorded HFT events with frequencies of over 40 Hz and few minutes length. On February 14th 2010, about three years and half after the first monitoring campaign another OBS/H was deployed in the same point for a long monitoring campaign (9 mouths). For this experiment the OBS/H was equipped with a Guralp CMG40T-OBS 3C seismometer, with flat transfer function in the band 60 s - 100 Hz, housed in a glass sphere with an autoleveling system that allows the sensor leveling in a range of ± 70° from the vertical. To monitor high frequency seismic and pressure signals the OBS/H was also equipped with a HTI-04- PCA/ULF Hydrophone, with a flat transfer function in the band 100s - 8 kHz. Both the signals were recorded by a 4 channels 21 bits SEND Geolon-MLS datalogger, at a sampling frequency of 200 Hz. During the nine months of the monitoring experiment the OBS/H recorded some thousand of little magnitude events very similar to that of the first experiment. The signals recorded in both the experiments were analyzed using polarization, spectral and clustering techniques. Both methods and results will be presented during the workshop.

Description: Published

Description: Salina Islands, Italy

Description: 2.5. Laboratorio per lo sviluppo di sistemi di rilevamento sottomarini

Description: open

Description: The Marsili, the biggest European volcano, can be considered as being the key needed to understand the dynamics of spreading and back-arc lithosphere formation in the Tyrrhenian sector (Marani et al., 2004, and references therein). Despite of its dimensions, due to its geographical position, it is very difficult to monitor (D'Alessandro et al., 2011) and it still remains little known. In 2006 the INGV staff deployed a broadband OBS/H (Mangano et al., 2011) on the Marsili’s flat top at a depth of about 790 m. In only 9 days, the instrument recorded about 800 seismo-volcanic events (D'Alessandro et al., 2009). This experiment, for the first time, revealed an intense seismo-volcanic activity of the Marsili. However, the short duration of the experiment didn’t allow to characterize, in an exhaustively way, the seismo-volcanic activities currently in act on the seamount. For this reason, on February the 14th 2010 another OBS/H was deployed in the same point for a long time experiment (9 months). During the monitoring campaign, the submarine station recorded some thousands of local little magnitude events. The entire data set was classified, on the basis of the time and frequency domain appearances following Wasserman (2002); we recognized 589 Volcano-Tectonic type A (VT-A) events and 1952 Volcano-Tectonic type B (VT-B) events (Fig. 1), measuring their local magnitude following Havskov et al. (2003). The seismogram of a typical VT-A event is dominated by P and S phases and by a short coda (Fig. 1a). These events are characterized by P phases with impulsive and high-amplitude onsets. The spectrogram shows broadband body phases with very high frequency and energy content extending up to 80 Hz (Fig. 1c). The VT-A events recorded have local magnitude between 0.5 and 3 and time length between 40 and 70 s. For these earthquakes, separation of P and S waves is clear and TS-TP is between 0.35 and 0.55 s. Their average recurrence time is about 2-3 events a week, with moderate variation in the observed period. The VT-B events are characterized by P phases with emergent and low-amplitude onsets (Fig. 1b ). The waveforms don't show any clear S wave arrival and they are featured by long coda (Fig. 1b). The VT-B events have time length between 15 and 40 s and local magnitude between -0.5 and 1.5. Their spectrograms shows a narrow frequency content (Fig. 1d). The time distribution of VT-B occurrence shows periods of moderate activity (some events a week) alternating with periods of intense activity (70 events a day). From Fig. 1f is also clear a time cyclic process and an upward trend in the VT-B activity. An increase in VT-B activity is often reported in some active volcanoes before significant eruptions. The observation of VT swarms on the Marsili volcano strongly suggest that it is still active. Further, it should not be ignored that potential volcanic eruptions could efficiently generate tsunami along the nearby coastlines.

Description: Published

Description: 213-214

Description: 2.5. Laboratorio per lo sviluppo di sistemi di rilevamento sottomarini

Description: JCR Journal

Description: open