What are the structure and temperature of the mantle transition zone in the North Atlantic? Insights from the SEA-SEIS ocean-bottom seismometer network

The existence, location and structure of the Iceland plume in the deep mantle are debated, in part due to the gap in seismic data sampling in the North Atlantic Ocean. To address this, in 2018-2020, a network of 18 ocean bottom seismometers (OBS) was deployed at 1–4 km depths on the North Atlantic seafloor by the project SEA-SEIS (Structure, Evolution and Seismicity of the Irish Offshore). Fourteen seismometers were recovered, of which 12 provided high-quality 3-component data. For these, we have obtained robust orientations of the horizontal components using Rayleigh-wave polarization.

 

To better understand the structure of the Iceland plume through the mantle transition zone, we aim to infer lateral temperature variations using Ps receiver functions. These receiver functions record P-to-S wave conversions from upgoing teleseismic waves beneath seismic stations, allowing us to estimate the depths of the main mantle transition zone discontinuities (the ‘410’ and ‘660’), which are temperature-dependent.

 

Reverberations of seismic waves within the water and sediment columns local to the seismometers, in addition to high levels of noise generated by ocean currents and waves, make calculation of receiver functions challenging. We test a variety of methods to produce useable receiver functions from the data. We present these, alongside receiver functions calculated for nearby onshore seismic stations, and latest tomography models, to make inferences on the temperature of the mantle transition zone.