The International Bathymetric Chart of the Arctic Ocean Version 4.0

Funder: The Nippon Foundation of Japan, grant Seabed 2030Funder: Open access funding provided by Stockholm UniversityAbstract: Bathymetry (seafloor depth), is a critical parameter providing the geospatial context for a multitude of marine scientific studies. Since 1997, the International Bathymetric Chart of the Arctic Ocean (IBCAO) has been the authoritative source of bathymetry for the Arctic Ocean. IBCAO has merged its efforts with the Nippon Foundation-GEBCO-Seabed 2030 Project, with the goal of mapping all of the oceans by 2030. Here we present the latest version (IBCAO Ver. 4.0), with more than twice the resolution (200 × 200 m versus 500 × 500 m) and with individual depth soundings constraining three times more area of the Arctic Ocean (∼19.8% versus 6.7%), than the previous IBCAO Ver. 3.0 released in 2012. Modern multibeam bathymetry comprises ∼14.3% in Ver. 4.0 compared to ∼5.4% in Ver. 3.0. Thus, the new IBCAO Ver. 4.0 has substantially more seafloor morphological information that offers new insights into a range of submarine features and processes; for example, the improved portrayal of Greenland fjords better serves predictive modelling of the fate of the Greenland Ice Sheet

GNSS and mareometer

La conoscenza della Terra non può prescindere dall’impiego di un riferimento altimetrico connesso al campo di gravità, sia per le applicazioni scientifiche che tecniche. Tradizionalmente la quota associata a un generico punto è riferita al livello medio del mare e, in Italia, l'Ente competente per l'osservazione e il monitoraggio di tale livello è l'Istituto Idrografico della Marina (IIM; DPR 90/2010). Internazionalmente oggi si privilegia però la scelta di assumere come riferimento per le altezze il geoide globale, ossia quella particolare superficie equipotenziale del campo di gravità convenzionalmente scelta dalla International Association of Geodesy (IAG). In Italia è pertanto necessario un ammodernamento infrastrutturale e procedurale con integrazione dell’infrastruttura mareometrica con Stazioni Permanenti per il posizionamento GNSS. Sarà così possibile uniformare il Datum di Altezza nazionale a quello globale, quale riferimento tempo-variante delle quote ortometriche depurato da effetti geodinamici. Si attendono positive ricadute per la stima del geoide gravimetrico, così come per il controllo della linea di costa e lo studio delle correnti stazionarie, con un potenziale accrescimento della conoscenza del dato climatologico.The knowledge of the territory cannot be obtained without the use of a height reference frame connected to the gravity field, both for scientific and technical applications. Traditionally, the height associated to a point whichever is referred to the mean sea level and, in Italy, the Institution in charge to measure and monitor of such a sea level is the Italian Navy Hydrographic Institute (IIM; DPR 90/2010). However, internationally the global geoid is commonly adopted as a reference for the height, i.e., that particular equipotential surface of the gravity field which is conventionally adopted by the International Association of Geodesy (IAG). Therefore, in Italy an infrastructural and procedural modernization is necessary through the integration of the mareometric infrastructure with Permanent Stations for GNSS positioning. Thus it will be possible to uniform the national Height Datum to the global one, as a time-dependent reference frame of orthometric heights which is made free from geodynamical effects. Positive consequences are expected for the gravimetric geoid estimation and for the coastline control and the study of stationary currents as well, with a potential increase in the knowledge of climatological data

Marine GIS as a Tool to Support Backscatter Data Analysis for Zooplankton Investigations

Echo-sounders and Vessel-Mounted Acoustic Doppler Current Profilers (VM-ADCP) are widely operating onboard research vessels with the aim of providing real-time backscatter and ocean current profiles along the route, while the vessel is moving. Backscatter data are exploited to infer important information about zooplankton presence and distribution. Nevertheless, as these organisms daily vertically migrate even below the depth of the instrument range, the combination of space and time variability make their mapping from a moving vessel quite complex. The objective of this work is to describe a GIS application developed for the management and analysis of these data. The GIS capability as a tool to facilitate zooplankton investigations is assessed by means of a test-case in the area of the Ligurian Sea (Western Mediterranean) by using VM-ADCP backscatter data made available during oceanographic campaigns. The system, which includes a high-resolution bathymetry, environmental parameters, ephemeris, allows to select and visualize data sorted according to all the possible layer combinations. Moreover, different backscatter profiles, characterizing the identified migration phases can be enlightened by means of false color scale representation

Detection and Characterization of Meteotsunamis in the Gulf of Genoa

A long-term time series of high-frequency sampled sea-level data collected in the port of Genoa were analyzed to detect the occurrence of meteotsunami events and to characterize them. Time-frequency analysis showed well-developed energy peaks on a 26–30 minute band, which are an almost permanent feature in the analyzed signal. The amplitude of these waves is generally few centimeters but, in some cases, they can reach values comparable or even greater than the local tidal elevation. In the perspective of sea-level rise, their assessment can be relevant for sound coastal work planning and port management. Events having the highest energy were selected for detailed analysis and the main features were identified and characterized by means of wavelet transform. The most important one occurred on 14 October 2016, when the oscillations, generated by an abrupt jump in the atmospheric pressure, achieved a maximum wave height of 50 cm and lasted for about three hours

Use of ICEsat-2 and Sentinel-2 Open Data for the Derivation of Bathymetry in Shallow Waters: Case Studies in Sardinia and in the Venice Lagoon

Despite the high accuracy of conventional acoustic hydrographic systems, measurement of the seabed along coastal belts is still a complex problem due to the limitations arising from shallow water. In addition to traditional echo sounders, airborne LiDAR also suffers from high application costs, low efficiency, and limited coverage. On the other hand, remote sensing offers a practical alternative for the extraction of depth information, providing fast, reproducible, low-cost mapping over large areas to optimize and minimize fieldwork. Satellite-derived bathymetry (SDB) techniques have proven to be a promising alternative to supply shallow-water bathymetry data. However, this methodology is still limited since it usually requires in situ observations as control points for multispectral imagery calibration and bathymetric validation. In this context, this paper illustrates the potential for bathymetric derivation conducted entirely from open satellite data, without relying on in situ data collected using traditional methods. The SDB was performed using multispectral images from Sentinel-2 and bathymetric data collected by NASA’s ICESat-2 on two areas of relevant interest. To assess outcomes’ reliability, bathymetries extracted from ICESat-2 and derived from Sentinel-2 were compared with the updated and reliable data from the BathyDataBase of the Italian Hydrographic Institute

Morpho-acoustic characterization of a shallow-water mud volcano offshore Scoglio d'Affrica (Northern Tyrrhenian Sea) responsible for a violent gas outburst in 2017

A violent gas outburst occurred offshore the Scoglio d'Affrica islet (Tuscan Archipelago, Northern Tyrrhenian Sea) on March 16th 2017, with local fishermen observing columns of dirty water rising up to 10 m above the sea surface. The integration of video footage and dissolved CH4 measurements collected 5 days after the event with high-resolution multibeam data collected 4 months later, allowed us to characterize the source area of the outburst, corresponding to a shallow-water mud volcano. The mud volcano covers an area of ca. 170,000 m2, has a vertical relief of ca. 30 m with respect to the surrounding seafloor and an estimated volume of ca. 1 × 106 m3, based on bathymetric reconstruction. The elongated NNW-SSE shape of the mud volcano is compatible with local structural trends, indicating a tectonic control for its development. The mud volcano is made up of two mounds whose tops are located at a depth of ca. 10 m. The southern mound was responsible for the 2017 outburst, as testified by a 15–20 m wide circular crater on its summit where a large amount of mud breccia and diffuse seepage from small pockmarks were observed in video footage . The flanks of the mud volcano are steep and characterized in the upper part by a hummocky morphology and multiple sediment flows on the western flank. The characterization of the mud volcano and the deposits associated with the 2017 gas outburst provides insight into seafloor-shaping processes linked to fluid seepage in shallow-water sectors. This is a particularly relevant issue considering both the paucity of studies on shallow-water mud volcanoes as well as the hazard associated with violent gas outbursts in such settings, as witnessed by the March 16th 2017 event

Seafloor characterisation of the offshore sector around Scoglio d’Affrica islet (Tuscan Archipelago, northern Tyrrhenian sea)

We present a very high-resolution bathy-morphological map of the offshore sector around the Scoglio d’Affrica islet (northern Tyrrhenian Sea, Italy). The study area covers a sector of 45 km2, between 3 and 85 m depth. Its central part, i.e. the apex of the Ridge, is characterised by a flat or gently sloping seafloor, where three mud volcanoes, and 250 pockmarks are recognised. Differently, the western and eastern Ridge flanks are steeper and characterised by 60 quasi-rectilinear escarpments and small ridges, more than 20 morphological highs, and elongated channels occasionally floored by bedforms. The seafloor shallower than 40 m is covered by Posidonia oceanica, forming compact and continuous or fragmented meadows intermingled with sandy patches. The main map represents the bathy-morphological setting of the area, which is largely affected by fluid seepage, providing insights for habitat mapping and preliminary marine geohazard assessment due to the violent gas outburst from mud volcanoes.</p

Relief preservation of a polar deep-sea channel system: the INBIS Channel (NW Barents Sea, Arctic)

34th International Association of Sedimentologists (IAS) Meeting of Sedimentology, Sedimentology to face societal challenges on risk, resources and record of the past, 10-13 September 2019, Rom

Depicting a high-latitude channel system: the INBIS Channel (NW Barents Sea)

European Geosciences Union (EGU) General Assembly 2018, 8-13 April 2018, Vienna, Austria.-- 1 pageThe INBIS (Interfan Bear Island and Storfjorden) Channel System is a rare example of deep-sea channel on andbeyond a glaciated continental margin. This channel system is located between the Bear Island and Kveithola-Storfjorden Trough Mouth Fans on the SW Barents Sea continental margin. A new compilation of bathymetry datashows that a series of 40 gullies, about 150-600 m wide and with incision depth of 10-60 m, incises the upperpart of the continental slope. These merge and increase in size downslope, transit into larger tributary channels andconverge into the INBIS Channel. The fringes of the INBIS tributary channels are buried below glacigenic debrisflows originating from the upper slope and shelf of the adjacent Trough-Mouth Fans during glacial maxima. Thissuggests that the INBIS Channel was not generated primarily by mass flows released at the mouth of the troughs.We infer that this gully-dominated part of the INBIS Channel System developed mainly in interglacial periodsfrom dense water cascading from the continental shelf and meltwaters. This gully-dominated part was relativelyprotected, by its location to the west of Bear Island, from recurrent glacigenic debris flows allowing meltwaters tocontinuously increase gullies (and channels) dimensions during interglacial periodsPeer Reviewe