5:15 PM - 7:15 PM
[MTT36-P04] 15 years of the GLISN seismic network in Greenland (2): Achievements
Keywords:Greenland, Seismic tomography, Ice sheet, Hot plumes and slabs
The GLISN seismic network in Greenland was completed in 2011, and the data accumulated over the past 15 years have been extensively analyzed (see another presentation "15 years of the GLISN seismic network in Greenland (1): Observations" in the S-SS05 session). This presentation reports the achievements primarily based on research by the presenters.
Ice Sheet
By comparing the observed Rayleigh waveforms extracted from ambient noise with theoretical waveforms, high attenuation (Qp, Qs) = (20, 20) of the ice sheet was revealed for the first time through ultra-long-distance (hundreds to thousands of kilometers) propagation (Toyokuni et al., 2021, JGR). Furthermore, the detection of seasonal and long-term variations in Rayleigh-wave phase velocity suggested the possibility of basal melting of the ice sheet in northern Greenland (Toyokuni et al., 2018, PEPI).
Upper Mantle
Regional P-wave tomography (Toyokuni et al., 2020a, JGR) revealed that regions with basal melting of the ice sheet are located at the intersection of the thermal tracks of the Iceland plume and the Jan Mayen plume, where the crustal heat flow may singularly be elevated. A hot plume was discovered beneath the Svalbard Islands in the upper mantle, which is called the Svalbard plume. A large high-velocity body (= the northeastern rock body) was revealed in the upper mantle off the northeastern coast of Greenland. This body is thought to be the remnant of the Iapetus Ocean lithosphere, which closed 490-390 Ma, and may have influenced the spreading style of the Mid-Atlantic Ridge. The region is located at the ridge where the Farallon slab, subducted beneath North America, and the Izanagi slab, subducted beneath Eurasia, were located close to each other. A long flat slab, formed by the accumulation of lighter ridge material in the mantle transition zone (MTZ), was identified (Toyokuni & Zhao, 2023, PEPS). The splitting of Greenland and Canada, along with related volcanic activity on the west coast, are considered to be caused by geodynamic processes in a big mantle wedge formed above this flat slab.
Lower Mantle
Global P-wave tomography (Toyokuni et al., 2020b, JGR) identified a hot plume (= the Greenland plume) rising from the core-mantle boundary (CMB) to the base of the MTZ beneath Greenland. The Jan Mayen and Svalbard plumes are considered to be branches of the Greenland plume in the upper mantle, split by the northeastern rock body. The Iceland plume is thought to be connected to the Greenland plume at two points and to another plume in Western Europe at one point. The existence of multiple heat supply routes likely explains the large number of active volcanoes in Iceland compared to its surrounding regions. Additionally, regional P-wave anisotropic tomography (Toyokuni & Zhao, 2021, ESS) estimated the mantle flow field around the Iceland plume.
Through the GLISN observations, a detailed structure beneath Greenland and surrounding regions, from the ice sheet to the CMB, has been revealed. Volcanic activity, geothermal activity, and ice sheet melting are now understood as part of a unified thermal system driven by the hot plume in the lower mantle and its branches. With continued data accumulation through network maintenance, further deepening of understanding in this region can be expected.
Ice Sheet
By comparing the observed Rayleigh waveforms extracted from ambient noise with theoretical waveforms, high attenuation (Qp, Qs) = (20, 20) of the ice sheet was revealed for the first time through ultra-long-distance (hundreds to thousands of kilometers) propagation (Toyokuni et al., 2021, JGR). Furthermore, the detection of seasonal and long-term variations in Rayleigh-wave phase velocity suggested the possibility of basal melting of the ice sheet in northern Greenland (Toyokuni et al., 2018, PEPI).
Upper Mantle
Regional P-wave tomography (Toyokuni et al., 2020a, JGR) revealed that regions with basal melting of the ice sheet are located at the intersection of the thermal tracks of the Iceland plume and the Jan Mayen plume, where the crustal heat flow may singularly be elevated. A hot plume was discovered beneath the Svalbard Islands in the upper mantle, which is called the Svalbard plume. A large high-velocity body (= the northeastern rock body) was revealed in the upper mantle off the northeastern coast of Greenland. This body is thought to be the remnant of the Iapetus Ocean lithosphere, which closed 490-390 Ma, and may have influenced the spreading style of the Mid-Atlantic Ridge. The region is located at the ridge where the Farallon slab, subducted beneath North America, and the Izanagi slab, subducted beneath Eurasia, were located close to each other. A long flat slab, formed by the accumulation of lighter ridge material in the mantle transition zone (MTZ), was identified (Toyokuni & Zhao, 2023, PEPS). The splitting of Greenland and Canada, along with related volcanic activity on the west coast, are considered to be caused by geodynamic processes in a big mantle wedge formed above this flat slab.
Lower Mantle
Global P-wave tomography (Toyokuni et al., 2020b, JGR) identified a hot plume (= the Greenland plume) rising from the core-mantle boundary (CMB) to the base of the MTZ beneath Greenland. The Jan Mayen and Svalbard plumes are considered to be branches of the Greenland plume in the upper mantle, split by the northeastern rock body. The Iceland plume is thought to be connected to the Greenland plume at two points and to another plume in Western Europe at one point. The existence of multiple heat supply routes likely explains the large number of active volcanoes in Iceland compared to its surrounding regions. Additionally, regional P-wave anisotropic tomography (Toyokuni & Zhao, 2021, ESS) estimated the mantle flow field around the Iceland plume.
Through the GLISN observations, a detailed structure beneath Greenland and surrounding regions, from the ice sheet to the CMB, has been revealed. Volcanic activity, geothermal activity, and ice sheet melting are now understood as part of a unified thermal system driven by the hot plume in the lower mantle and its branches. With continued data accumulation through network maintenance, further deepening of understanding in this region can be expected.