Search

El Hierro, the smallest, youngest and westernmost island of the Canarian archipelago, with an area of 278 Km2, is settled on an ocean floor 3.5 km deep and reaches 1.5 km above sea level. The island was constructed by rapid constructive and destructive processes in ~ 1.12 Ma. From October 2011 to March 2012 a submarine eruption took place about 2 km south of the small village of La Restinga in the southernmost part of the island. The eruptive process has been the second longest and the second largest volume discharged in the historical volcanic activity of the Canaries (in the last 500 years) and was the first one to be monitored from the beginning. One of the most useful geochemical tools to monitor the volcanic activity of El Hierro is the diffuse degassing studies, since visible volcanic emissions are absent at the surface of El Hierro. Diffuse CO2 emissions have been monitored at El Hierro Island since 1998 in a yearly basis, with higher frequency during the pre and eruptive periods. At each survey, 600 sampling sites are studied and measurements of soil CO2 efflux were performed in situ following the accumulation chamber method (Parkinson, 1981). During pre-eruptive and eruptive periods, the diffuse CO2 emission released by the whole island experienced significant increases before the onset of the submarine eruption and the most energetic seismic events of the volcanic-seismic unrest. In the last survey, performed in the 2018 summer period, soil CO2 efflux values ranged from non-detectable to 31 g•m−2•d−1. Statistical-graphical analysis of the data show three different geochemical populations, background (B), intermediate (I) and peak (P), represented by 90.9%, 7.8 % and 1.3% of the total data respectively, with geometric means of 1.1, 12 and 22 g•m−2•d−1, respectively. To quantify the diffuse CO2 emission for the 2018 survey, 100 sequential Gaussian simulations (sGs) were performed as interpolation method. The estimated 2018 diffuse CO2 output released to atmosphere by El Hierro was at 654 ± 26 t•d-1, value higher than the background average of CO2 emission estimated in 422 t•d-1. The data presented here demonstrate that discrete surveys of diffuse CO2 emission offer important information to optimize the early warning system in volcano monitoring programs and to monitor the evolution of an on-going volcanic eruption. [ABSTRACT FROM AUTHOR]

The canary archipelago is a low seismicity area with low magnitude events. Our interest in this region is focused on detecting and locating events occurred during drilling operations and the analysis of harmonic tremors. We take data from an Ocean Bottom Seismometer array (17 OBSs) deployed during two months in the eastern Island archipelago. Array methods are suitable to highlight detection of seismic events and locate its sources. We analyze with a new methodology incoherent signals across the OBSs large aperture array. The proposed methodology estimates the Hilbert transform time-frequency plane to find impulsive characteristic functions and subsequently the impulsive functions are stacked to derive the slowness vector of incoming seismic transient signals. We will show results of source locations from short duration harmonic tremors and seismic events occurred during the drilling activities. [ABSTRACT FROM AUTHOR]

EMSO ERIC, the "European Multidisciplinary Seafloor and water column Observatory", has developed an EMSO Generic Instrument Module, called EGIM, in the frame of the H2020 project "EMSO-Dev". The module aims at consistently and continuously measuring seven Essential Ocean Variables for the science areas at the various regional facilities pertaining to EMSO, placed at key sites around the European seas.The EGIM core variables include temperature, conductivity, pressure, dissolved O2, turbidity, ocean currents, and passive acoustics. These parameters are of great interest for different disciplines, ranging from geosciences to physical oceanography, to biogeochemistry and marine ecology addressing Grand Challenges such as ocean acidification and warming. They also support the Global Ocean Observing System, and the Marine Strategy Framework Directive towards evaluating environmental status of the European seas. The EGIM is designed to adapt to the various EMSO node configurations: mooring line, cabled or non-cabled sea bed station and surface buoy. Its compact and modular nature, low power requirements, mechanical design and embedded software allow for flexible deployment scenarios and can accommodate new instruments. This are key points to the modularity, inter-operability and capacity of the future evolution of the EGIM.In July 2017, after a 4-month shallow water test period on OBSEA observatory offshore Barcelona, the EGIM prototype was installed on EMSO-Azores observatory on the mid-atlantic ridge, at a 1700 m water depth (https://campagnes.flotteoceanographique.fr/campagnes/17000500/),. It was set at the Lucky Strike hydrothermal vent site, to monitor local hydrodynamic variability and complement the data obtained by the numerous sensors set on this site: oceanographic mooring deployed south of the vent field, the multidisciplinary SeaMoN East node, autonomous current meters, array of temperature probes (http://www.emso-fr.org/fr/EMSO-Azores)... The recovery took place in August 2018 and the data are made available through precisely documented DOIs referenced in EMSO data catalogue.Replicated units of the EGIM are ready for pending deployments on other EMSO nodes. One of them will be connected to the Western Ionian node (East of Sicily) at the end of the north branch of the cable which runs from Catania. The second one will be deployed in the Atlantic Ocean, near the Canary Islands, under different configurations including open-ocean mooring on ESTOC site. Using the EGIM as a common EOV measurement reference for all nodes is a crucial step towards standardization, increasing global reliability, data quality and reducing costs across EMSO consortium. The EGIM can be considered as a milestone to meet the marine community need for of standardization and interoperability.(1) Funding from the European Union's Horizon 2020 research and innovation program under grant agreement N°676555. [ABSTRACT FROM AUTHOR]