Electromagnetic Array Research over a Tectonic Hotspot (EARTH)

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In 2010, Iceland's volcanism claimed worldwide attention when international flights were cancelled due to ash clouds spewing from the erupting Eyjafjallajökull volcano, leaving thousands of passengers stranded. The source of Iceland's volcanism is highly controversial. Iceland is intersected by the mid-Atlantic Ridge where tectonic plates are rifting apart. However, upwelling of magma due to rifting cannot explain the region's elevation or the amount and geochemical compositions of melts, leading to the hypothesis that a mantle plume of hot material with a deep source underlies the Iceland hotspot. However, the nature, spatial extent, depth of genesis - core-mantle boundary (CMB) versus mid-mantle transition zones (410-660 km depth) - indeed, very existence of the Iceland plume are issues that are highly debated. Recent seismological models suggest that a mantle plume may rise from below Greenland, be deflected by topography at the underside of the North American tectonic plate towards Iceland and extend below the plate as far as the British Isles.With hundreds of millions of people's lives globally impacted by volcanic activity, it is essential to understand what drives eruptions by mapping magma below Earth's surface to allow mitigation strategies to be devised. 3D models of electrical conductivities and seismic velocities provide complementary information for imaging volcanic magmas because electrical conductivities and seismic velocities are affected differently by melt quantity, distribution, composition and temperature. Magnetotellurics (MT) is a geophysical technique that uses natural electric and magnetic fields induced in the Earth by interactions between the solar wind (a stream of high-energy charged particles from the Sun) and Earth's magnetosphere (a protective shield around the Earth maintained by Earth's magnetic field) to characterize Earth's electrical conductivity structure. I propose MT array measurements in Scotland, Iceland and Greenland to complement existing seismological data. The 3D electrical conductivity models of Earth's mantle and joint inversions of electromagnetic, seismological and physicochemical data that I produce will unequivocally solve controversies relating to the nature of the Iceland hotspot that cannot be addressed using a single geophysical method.It is imperative that modern societies balance their greed for energy with measures to mitigate against further anthropogenic production of greenhouse gases that drive climate change. In the UK, this realization is leading to the development of offshore wind power and proposals to bring geothermally generated, low carbon electricity from Iceland to the UK mainland via a high-voltage (HV) cable called the Atlantic Superconnection. However, development of offshore renewable energy will expose our HV power transmission network to greater risk from space-weather induced power blackouts, because hazardous geomagnetically induced currents (GICs) that flow in transmission lines during magnetic storms increase in proportion to transmission-line lengths, which can be expected to increase significantly. Space weather is listed on the National Risk Register as a medium-to-high likelihood event associated with medium-impact socioeconomic risk and the UK government recognizes the need for improved capability to forecast extreme space weather events and their impacts on ground-based technological infrastructure to enable mitigation strategies to be devised. The scaling between storm-time magnetic fields and the GICs they induce and, therefore, the vulnerability of different geographic regions to magnetic storms is determined by Earth's deep, 3D electrical conductivity structure. As well as providing constraints on the Iceland plume, my MT products will include estimates of storm-time electric fields, worst-case-scenario space weather hazard maps and probabilistic forecasts, with a particular focus on the HV subsea cable from Iceland to the UK.