Exploiting the ANN Potential in Estimating Snow Depth and Snow Water Equivalent From the Airborne SnowSAR Data at X- and Ku-Bands

Within the framework of European Space Agency (ESA) activities, several campaigns were carried out in the last decade with the purpose of exploiting the capabilities of multifrequency synthetic aperture radar (SAR) data to retrieve snow information. This article presents the results obtained from the ESA SnowSAR airborne campaigns, carried out between 2011 and 2013 on boreal forest, tundra and alpine environments, selected as representative of different snow regimes. The aim of this study was to assess the capability of X- and Ku-bands SAR in retrieving the snow parameters, namely snow depth (SD) and snow water equivalent (SWE). The retrieval was based on machine learning (ML) techniques and, in particular, of artificial neural networks (ANNs). ANNs have been selected among other ML approaches since they are capable to offer a good compromise between retrieval accuracy and computational cost. Two approaches were evaluated, the first based on the experimental data (data driven) and the second based on data simulated by the dense medium radiative transfer (DMRT). The data driven algorithm was trained on half of the SnowSAR dataset and validated on the remaining half. The validation resulted in a correlation coefficient R ≃ 0.77 between estimated and target SD, a root-mean-square error (RMSE) ≃ 13 cm, and bias = 0.03 cm. ANN algorithms specific for each test site were also implemented, obtaining more accurate results, and the robustness of the data driven approach was evaluated over time and space. The algorithm trained with DMRT simulations and tested on the experimental dataset was able to estimate the target parameter (SWE in this case) with R = 0.74, RMSE = 34.8 mm, and bias = 1.8 mm. The model driven approach had the twofold advantage of reducing the amount of in situ data required for training the algorithm and of extending the algorithm exportability to other test sites

First Multi Beam and high resolution reflection seismics on the Tiber River lower course

The use of multi-beam in the study of the Tiber river morfologie

Gas related features offshore the western Pontine Islands (Tyrrhenian Sea)

Several seafloor depressions have been found on the seafloor around the Western Pontine Archipelago (Palmarola, Ponza and Zannone Islands) located around 30 km away from the Latium coast. By the integration of different geophysical data have been possible to identify specific gas related structures as little pockmarks and large depressions located both on the continental shelf and upper slope. The large depressions are located few kilometers away from the Zannone Island at depths between 105 and 140 m. They have an average surface of 0.25 km2 and are 10 m deep compared to the surrounding seafloor. Other gas related features have been found in the north-western sector of Palmarola Island (depth between 60 and 90 m), in the southern sector of Ponza Island (depth between 130 and 140 m) and in the northern sector of the archipelago (depth between 200 and 400 m). Video observations (by Remotely Operated Vehicle) acquired across the depressions placed offshore the Zannone Island, were use

Fluid emission affecting lowstand shelf deposits on the flank of a volcanic island (Zannone Island, Tyrrhenian Sea, Italy).

Several Gas Related Features (GRFs) have been detected offshore the Western Pontine Archipelago by means of very high resolution multibeam bathymetry, high resolution seismic profiles, ROV video observations, water and sediment sampling. Importance of GRFs is related to their association with hydrocarbon occurrence in the subsurface, settlement of endemic ecosystems and the possible direct or indirect linkage with marine geohazards (submarine slides, earthquakes, damage to seafloor infrastructures). In particular, at a broader spatial and temporal scale, geological emissions of methane may be take into consideration as geological factors controlling Quaternary atmospheric and climate changes. Pontine Archipelago is located 30 kilometers from the Italian peninsula (Eastern Tyrrhenian Sea) and is composed of five Plio-Pleistocene volcanic islands: Ponza, Palmarola, Zannone (western sector) and Ventotene and S. Stefano (eastern sector). The research is focused on specific GRFs located offshore the eastern sector of Zannone Island, at water depth ranging between 105-130 m (outer continental shelf). GRFs comprise: giant pockmark, several pockmarks and dome topographic features. The giant pockmark has elongated shape and is 900 m long and 500 m wide; pockmarks are characterized by circular, sub-circular and elongated shapes with dimensions ranging between 2-80 m; whereas dome topographic features are mostly cone-shaped structures with dimensions between 8-36 m. ROV observations have revealed the occurrence of active fluid emissions escaping from the seafloor, characterized by different discharge modalities (continuous and intermittent) and presence of widespread bacterial mats, possible chemosynthetic bivalve aggregations, small scales cone structures and several burrows linked to bioturbation and/or fluid escaped. Moreover, water column backscatter data acquired by multibeam have revealed the occurrence of plumes extended to at least 70 m into the water column. Analysis of very high seismic profiles show the occurrence of several flares at the same location of plumes individuated by water column backscatter data and the occurrence of lowstand prograding deposits, covered by a few meters thick of Holocene deposits. Lowstand prograding deposits have a max thickness of about 35 m and across the giant pockmark show a chaotic seismic facies, indicating intense deformation. To date, rare cases of active shallow-water cold seeps have been described in the Mediterranean Sea. Analysis of the morphological, sedimentological and stratigraphic characteristics of the study area provide the first evidence of an active shallow-water cold emission site in the Eastern Tyrrhenian Sea

On the retrieval of internal temperature of Antarctica Ice Sheet by using SMOS observations

International audienc

The Zannone Giant Pockmark. First evidence of a giant complex seeping structure in shallow-water, central Mediterranean Sea, Italy

An active giant pockmark located offshore Zannone Island (central Tyrrhenian Sea, Italy), is analyzed by very high resolution multibeam bathymetry, high resolution seismic profiles, ROV video observations, sediment and water sampling. The active fluid emission area is located on the outer shelf, between 110 and 130 m water depth, and affects the Late Quaternary lowstand and highstand deposits resting on rocky bedrock. A variety of fluid-escape features characterizes the area, including the Zannone giant pockmark, several smaller pockmarks, hummocky terrains and areas of positive relief. Ground-truth video data show active seepages, bacterial communities, widespread lithified pavements, mounds, and cone-shaped structures. Evidence of active seepage includes both continuous and intermittent bubble release from the seafloor and a well-defined plume rising 70 m above the seafloor. The Zannone giant pockmark is about 900 × 500 m (surface of some 0.5 km2). It represents the first evidence of an active shallow-water seepage area in the central Tyrrhenian Sea (Italy) and the first record of a morphologically complex giant pockmark in the entire Mediterranean Sea. Some speculations on processes originating the observed features are explored, including possible occurrence of multiple eruption events, processes of fluidization–liquefaction and minor slides that may have modified the original morphology. Factors peculiar to the study area – shallow depth, thin sedimentary cover resting on a faulted rocky basement, seeping occurring through non-cohesive sandy sediments appear to have been key to the formation and morphology of the Zannone giant pockmark