A team of researchers understands more about the melting of the Greenland ice sheet. They discovered a flow of hot rocks, known as a mantle plume, rising from the core-mantle boundary beneath central Greenland that melts the ice from below.
The results of their two-part study were published in the Journal of Geophysical Research.
“Knowledge about the Greenland plume will bolster our understanding of volcanic activities in these regions and the problematic issue of global sea-level rising caused by the melting of the Greenland ice sheet,” said Dr. Genti Toyokuni, co-author of the studies.
The North Atlantic region is awash with geothermal activity. Iceland and Jan Mayen contain active volcanoes with their own distinct mantle plumes, whilst Svalbard — a Norwegian archipelago in the Arctic Ocean — is a geothermal area. However, the origin of these activities and their interconnectedness has largely been unexplored.
The research team discovered that the Greenland plume rose from the core-mantle boundary to the mantle transition zone beneath Greenland. The plume also has two branches in the lower mantle that feed into other plumes in the region, supplying heat to active regions in Iceland and Jan Mayen and the geothermal area in Svalbard.
Their findings were based on measurements of the 3-D seismic velocity structure of the crust and whole mantle beneath these regions. To obtain the measurements, they used seismic topography. Numerous seismic wave arrival times were inverted to obtain 3-D images of the underground structure. The method works similarly to a CT scan of the human body.
Toyokuni was able to utilize seismographs he installed on the Greenland ice sheet as part of the Greenland Ice Sheet Monitoring Network. Set up in 2009, the project sees the collaboration of researchers from 11 countries. The US-Japan joint team is primarily responsible for the construction and maintenance of the three seismic stations on the ice sheet.
Looking ahead, Toyokuni hopes to explore the thermal process in more detail. “This study revealed the larger picture, so examining the plumes at a more localized level will reveal more information.”
References:
“P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle” by Genti Toyokuni, Takaya Matsuno and Dapeng Zhao, 31 October 2020, Journal of Geophysical Research – Solid Earth.
DOI: 10.1029/2020JB019837
“P Wave Tomography Beneath Greenland and Surrounding Regions: 2. Lower Mantle” by Genti Toyokuni, Takaya Matsuno and Dapeng Zhao, 30 October 2020, Journal of Geophysical Research – Solid Earth.
DOI: 10.1029/2020JB019837
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5 Comments
“…, they used seismic topography.”
That should be “tomography,” NOT topography!
“This study revealed the larger picture, so examining the plumes at a more localized level will reveal more information.”
It goes a long way towards explaining why Eastern Greenland has experienced greater retreat of its glaciers than Western Greenland!
I wonder how much global warming is coming from the melting icecap. I’m certainly not disputing climate change from human effects, but wonder how much this is contributing. It will surely not explain melting in the Antarctic. It will be interesting to see how the effects of this plume will affect future models.
Mary there is an active volcanp beneath the West Antarctic ice shelf. Nobody knows for sure how many active volcanos there are on Earth. Nobody really has concrete notions how the Earth’s magnetic fields work. Nobody can tell you why the Earth’s magnetic northpole is moving towards Russia at an increasing pace. Everybody assumes that the present assemblage of the Solar system is the way it has always been but just because of how they are now is no proof of what they may have been in the past. Imagine how that would have effected the Earth’s climate as the Earth orbits the center of gravitly of the Solar systen and not the center of gravity of the Sun. So the Earth’s orbit is not an ellipse but a rosette as the Sun is moving also. It is also an assumption that the Sun’s output that has only been accurately measured for less than a hundred years is what it has always been. A person like me thinks it is absurd to believe that man made CO2 is acting like the control knob of the climate. All the ice cores say the temperature changes and then the CO2 level changes.It is certainly not settled as to why the Ice ages start and end. Or why they changed to to have somewhat 100,000 year cycles from the previous somewhat 40,000 cycles. Or why there was the younger dryas when global temperatures plummented and then rose 10C in a decade but hey the climate science is settled
Brilliant Summary in a very kind letter to Mary,