THIS POST IS A RESPONSE TO A SCIENCE-ALERT ARTICLE OF OCTOBER 2020 THAT CLIMATE CHANGE IS CHANGING THE SHAPE OF GREENLAND’S COASTLINE WITH THE IMPLICATION THAT THESE CHANGES CAN AND MUST BE STOPPED BY TAKING CLIMATE ACTION. LINK TO SCIENCE-ALERT ARTICLE: https://www.sciencealert.com/melting-ice-is-changing-greenland-s-coast-impacting-on-its-marine-ecosystems

And from the Centre for International Governance Innovation we have this: If We Protect the Arctic, We Save the Planet. October 3, 2019:

LINK: https://www.cigionline.org/articles/if-we-protect-arctic-we-save-planet

HERE WE PRESENT THE CASE THAT THE REGION IN QUESTION IS GEOLOGICALLY ACTIVE WITH MAGMATIC AND VOLCANIC ACTIVITY ALONG THE JAN MAYEN TREND AND THE GREENLAND-ICELAND MANTLE PLUME AND THAT THEREFORE A PURELY ATMOSPHERIC INTERPRETATION OF ICE MELT EVENTS IN THIS REGION IS NOT POSSIBLE WITHOUT SIGNIFICANT AND UNBIASED EVIDENCE OF SUCH CAUSATION.

The relevant geological features of the Arctic are described in a related post: LINK: https://tambonthongchai.com/2019/07/01/arctic/ . It is noted that there is significant geological activity in the form of volcanism and mantle flows around and under Iceland and Greenland that derive from the Mid Arctic Rift, the Greenland-Iceland mantle plume and the Baffin Bay-Labrador rift system. Geothermal heat flux from these seafloor activities play an important role in Greenland ice sheet and sea ice dynamics in the Arctic and therefore these phenomena cannot be understood purely in terms of atmospheric forcing implied by anthropogenic global warming. This is why sea ice melt dynamics do not correspond with global warming temperature as shown in related posts on this site. LINK: https://tambonthongchai.com/2020/09/25/list-of-arctic-sea-ice-posts/ .

The bibliography below provides additional support for this thesis. The role of anthropogenic global warming in these events can only be understood in the context of these geothermal heat fluxes. More importantly, the role of anthropogenic global warming in these ice melt dynamics derived exclusively from an atmosphere bias is not credible.

The science alert presentation on the exclusive role of anthropogenic global warming in coastal ice melt phenomena in Greenland is therefore also not credible. Analyses of this nature are likely derived from advocacy and they must therefore be understood more in terms of confirmation bias than objective scientific inquiry. LINK: https://tambonthongchai.com/2018/08/03/confirmationbias/

THE RELEVANT BIBLIOGRAPHY

1. Rysgaard, Søren, et al. “High geothermal heat flux in close proximity to the Northeast Greenland Ice Stream.” Scientific reports 8.1 (2018): 1-8. The Greenland ice sheet (GIS) is losing mass at an increasing rate due to surface melt and flow acceleration in outlet glaciers. Currently, there is a large disagreement between observed and simulated ice flow, which may arise from inaccurate parameterization of basal motion, subglacial hydrology or geothermal heat sources. Recently it was suggested that there may be a hidden heat source beneath GIS caused by a higher than expected geothermal heat flux (GHF) from the Earth’s interior. Here we present the first direct measurements of GHF from beneath a deep fjord basin in Northeast Greenland. Temperature and salinity time series (2005–2015) in the deep stagnant basin water are used to quantify a GHF of 93 ± 21 mW m⁻² which confirm previous indirect estimated values below GIS. A compilation of heat flux recordings from Greenland show the existence of geothermal heat sources beneath GIS and could explain high glacial ice speed areas such as the Northeast Greenland ice stream. LINK TO FULL TEXT: https://www.nature.com/articles/s41598-018-19244-x?fbclid=IwAR2i5VghxAuDlzyvIpeWDOKbth1dMfB5ERMSvhqrS9XDGFYOnJ4bQzD7eAM
2. van der Veen, Cornelis J., et al. “Subglacial topography and geothermal heat flux: Potential interactions with drainage of the Greenland ice sheet.” Geophysical research letters 34.12 (2007). Many of the outlet glaciers in Greenland overlie deep and narrow trenches cut into the bedrock. It is well known that pronounced topography intensifies the geothermal heat flux in deep valleys and attenuates this flux on mountains. Here we investigate the magnitude of this effect for two subglacial trenches in Greenland. Heat flux variations are estimated for idealized geometries using solutions for plane slopes derived by Lachenbruch (1968). It is found that for channels such as the one under Jakobshavn Isbræ, topographic effects may increase the local geothermal heat flux by as much as 100%. LINK TO FULL TEXT: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2007GL030046
3. Alley, R. B., et al. “Possible role for tectonics in the evolving stability of the Greenland Ice Sheet.” Journal of Geophysical Research: Earth Surface 124.1 (2019): 97-115. The history of the Greenland Ice Sheet has been influenced by the geodynamic response to ice sheet fluctuations, and this interaction may help explain past deglaciations under modest climate forcing. We hypothesize that when the Iceland hot spot passed beneath north‐central Greenland, it thinned the lithosphere and left anomalous heat likely with partially melted rock; however, it did not break through the crust to supply voluminous flood basalts. Subsequent Plio‐Pleistocene glacial‐interglacial cycles caused large and rapidly migrating stresses, driving dike formation and other processes that shifted melted rock toward the surface. The resulting increase in surface geothermal flux favored a thinner, faster‐responding ice sheet that was more prone to deglaciation. If this hypothesis of control through changes in geothermal flux is correct, then the long‐term (10⁵ to 10⁶ years) trend now is toward lower geothermal flux, but with higher‐frequency (≤10⁴ to 10⁵ years) oscillations linked to glacial‐interglacial cycles. Whether the geothermal flux is increasing or decreasing now is not known but is of societal relevance due to its possible impact on ice flow. We infer that projections of the future of the ice sheet and its effect on sea level must integrate geologic and geophysical data as well as glaciological, atmospheric, oceanic, and paleoclimatic information.
4. Greve, Ralf. “Geothermal heat flux distribution for the Greenland ice sheet, derived by combining a global representation and information from deep ice cores.” Polar Data Journal 3 (2019): 22-36. We present a distribution of the geothermal heat flux (GHF) for Greenland, which is an update of two earlier versions by Greve (2005, Ann. Glaciol. 42) and Greve and Herzfeld (2013, Ann. Glaciol. 54). The GHF distribution is constructed in two steps. First, the global representation by Pollack et al. (1993, Rev. Geophys. 31) is scaled for the area of Greenland. Second, by means of a paleoclimatic simulation carried out with the ice sheet model SICOPOLIS, the GHF values for five deep ice core locations are modified such that observed and simulated basal temperatures match closely. The resulting GHF distribution generally features low values in the south and the north-west, whereas elevated values prevail in central North Greenland and towards the north-east. The data are provided as NetCDF files on two different grids (EPSG:3413 grid, Bamber grid) that have frequently been used in modelling studies of the Greenland ice sheet, and for the three different resolutions of 5 km, 10 km and 20 km.
5. Smith-Johnsen, Silje, Basile de Fleurian, and Kerim H. Nisancioglu. “The role of subglacial hydrology in ice streams with elevated geothermal heat flux.” Journal of Glaciology 66.256 (2020): 303-312. The spatial distribution of geothermal heat flux (GHF) under ice sheets is largely unknown. Nonetheless, it is an important boundary condition in ice-sheet models, and suggested to control part of the complex surface velocity patterns observed in some regions. Here we investigate the effect of including subglacial hydrology when modelling ice streams with elevated GHF. We use an idealised ice stream geometry and a thermomechanical ice flow model coupled to subglacial hydrology in the Ice Sheet System Model (ISSM). Our results show that the dynamic response of the ice stream to elevated GHF is greatly enhanced when including the interactive subglacial hydrology. On the other hand, the impact of GHF on ice temperature is reduced when subglacial hydrology is included. In conclusion, the sensitivity of ice stream dynamics to GHF is likely to be underestimated in studies neglecting subglacial hydrology.
6. Mordret, Aurélien. “Uncovering the Iceland hot spot track beneath Greenland.” Journal of Geophysical Research: Solid Earth 123.6 (2018): 4922-4941. During the past 120 Ma, the Greenland craton drifted over the Iceland hot spot; however, uncertainties in geodynamic modeling and a lack of geophysical evidence prevent an accurate reconstruction of the hot spot track. I image the Greenland lithosphere down to 200‐km depth with both group and phase velocity seismic noise tomography. The 3‐D shear wave velocity model obtained using 4–5 years of continuous seismic records from the Greenland Ice Sheet Monitoring Network is well resolved for most of the Greenland main island. The crustal part of the model clearly shows different tectonic units. The hot spot track is observed as a linear high‐velocity anomaly in the middle and lower crust associated with magmatic intrusions. In the upper mantle, a pronounced low‐velocity anomaly below the east coast might be due to the remnant effect of the Iceland hot spot when it was at its maximum intensity. Thermomechanical modeling suggests that this area has higher temperature and lower viscosity than the surrounding cratonic areas and experiences a higher than average surface heat flow. This new detailed picture of the Greenland lithosphere will drive more accurate geodynamic reconstructions of tectonic plate motions and help to better understand the North Atlantic tectonic history. Models of Greenland glacial isostatic adjustment will benefit from the 3‐D upper‐mantle viscosity model, which in turn will enable more precise estimations of the Greenland ice sheet mass balance. Plain Language Summary: The ice sheet covering most of Greenland prevents scientists to know the geology and composition of the crust and therefore prevents them to understand the history of Greenland. Seismic tomography can be used to make images of the internal structure of the Earth below the ice and down to several hundreds of kilometers depth. Generally, seismologists use the waves generated by earthquakes to scan the Earth, but Greenland lacks of a sustained seismicity. Here I used the tiny ambient vibrations coming from the interactions between the oceanic waves and the continent, recorded during several years, to overcome this difficulty and reveal the internal structure of the Greenland lithosphere. I show that Greenland crust is made of several tectonic units separated by a track of volcanic intrusions left behind by the Iceland hot spot when it was below Greenland, about 60 Ma ago. The hot spot also lets a distinctive temperature anomaly in the upper mantle that still influences nowadays the dynamics of the whole continent and the ice sheet on top of it.
7. Nielsen, Thomas K., Hans Christian Larsen, and John R. Hopper. “Contrasting rifted margin styles south of Greenland: implications for mantle plume dynamics.” Earth and Planetary Science Letters 200.3-4 (2002): 271-286. We present new and reprocessed seismic reflection data from the area where the southeast and southwest Greenland margins intersected to form a triple junction south of Greenland in the early Tertiary. During breakup at 56 Ma, thick igneous crust was accreted along the entire 1300-km-long southeast Greenland margin from the Greenland Iceland Ridge to, and possibly ∼100 km beyond, the triple junction into the Labrador Sea. However, highly extended and thin crust 250 km to the west of the triple junction suggests that magmatically starved crustal formation occurred on the southwest Greenland margin at the same time. Thus, a transition from a volcanic to a non-volcanic margin over only 100–200 km is observed. Magmatism related to the impact of the Iceland plume below the North Atlantic around 61 Ma is known from central-west and southeast Greenland. The new seismic data also suggest the presence of a small volcanic plateau of similar age close to the triple junction. The extent of initial plume-related volcanism inferred from these observations is explained by a model of lateral flow of plume material that is guided by relief at the base of the lithosphere. Plume mantle is channelled to great distances provided that significant melting does not take place. Melting causes cooling and dehydration of the plume mantle. The associated viscosity increase acts against lateral flow and restricts plume material to its point of entry into an actively spreading rift. We further suggest that thick Archaean lithosphere blocked direct flow of plume material into the magma-starved southwest Greenland margin while the plume was free to flow into the central west and east Greenland margins. The model is consistent with a plume layer that is only moderately hotter, ∼100–200°C, than ambient mantle temperature, and has a thickness comparable to lithospheric thickness variations, ∼50–100 km. Lithospheric architecture, the timing of continental rifting and viscosity changes due to melting of the plume material are therefore critical parameters for understanding the distribution of magmatism.
8. Steinberger, Bernhard, et al. “Widespread volcanism in the Greenland–North Atlantic region explained by the Iceland plume.” Nature Geoscience 12.1 (2019): 61-68. In the classical concept, a hotspot track is a line of volcanics formed as a plate moves over a stationary mantle plume. Defying this concept, intraplate volcanism in Greenland and the North Atlantic region occurred simultaneously over a wide area, particularly around 60 million years ago, showing no resemblance to a hotspot track. Here, we show that most of this volcanism can nonetheless be explained solely by the Iceland plume interacting with seafloor spreading ridges, global mantle flow and a lithosphere (the outermost rigid layer of the Earth) with strongly variable thickness. An east–west corridor of thinned lithosphere across central Greenland, as inferred from new, highly resolved tomographic images, could have formed as Greenland moved westward over the Iceland plume between 90 and 60 million years ago. Our numerical geodynamic model demonstrates how plume material may have accumulated in this corridor and in areas east and west of Greenland. Simultaneous plume-related volcanic activities starting about 62 million years ago on either side of Greenland could occur where and when the lithosphere was thin enough due to continental rifting and seafloor spreading, possibly long after the plume reached the base of the lithosphere.

FIRE BELOW. ICE ABOVE. (NASA) LINK: https://climate.nasa.gov/news/2844/fire-below-ice-above-volcanoes-glaciers-and-sea-level-rise/

By Pat Brennan, NASA’s Sea Level Change Portal.

The movement of continents is far slower than a snail’s pace. It’s more like watching your fingernails grow. But speed up the movie over tens of millions of years and it begins to look like a demolition derby. Riding over Earth’s mantle on strong but flexible plates, the continents smash together and tear themselves apart, creating rugged mountain chains or deep ocean trenches. Hot magma from below the crust can rise toward the surface, like a blister pushing up below the skin. These gas and liquid-rich rocks create volcanoes. And they are created by hot spots – buoyant material that rises from more than 400 miles (660 kilometers) down, or even as deep as the core-mantle boundary. The ocean crust and continental plates glide over these hot spots through time, leaving scars over millions of years that reveal the plates’ paths. New seismic data and analysis, along with mechanical modeling capabilities, are allowing scientists to get to know these previously cryptic features a little better. And they are turning out to be potentially important when it comes to predicting how quickly the glaciers of Greenland and Antarctica will flow into the sea, reducing ice mass in the polar regions and raising sea levels. The heat welling up from Earth’s interior beneath ice sheets and glaciers has nothing to do with the relatively rapid change in climate over recent decades, driven mainly by human emissions of greenhouse gases that warm the atmosphere. Heat sources from the deep Earth can remain steady for 50, 90 or 100 million years; human-driven climate change is occurring over mere decades and centuries. Easing glacial speed limits. But as the coastal ice shelves that hold back glaciers begin to thin and melt away, the glaciers – essentially rivers of ice – are suddenly free to flow more quickly. If their channels happen to carry them over hot spots in the mantle, they can flow all the faster. “Heat content within an ice sheet raises the temperature, and therefore lowers viscosity” of the ice at the base of the glacier, said Erik Ivins, a senior research scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. The result: lubrication of the glacier’s movement. “It’s capable of expelling ice mass through faster flow,” Ivins said. A dramatic example is found in Greenland, where a long “thermal track” was recently revealed beneath the miles-thick ice sheet that covers the giant island. This scar tells an 80-million-year story. As the North American continental plate carried Greenland north, it glided over a relatively stationary hot spot – the same spot that later formed Iceland after Greenland had moved on, leaving the hot spot to punch out a new land mass from the crust beneath the sea. Tracing Greenland’s movement over 100 million years, carrying it over a hot spot that later formed Iceland. Credit: NASA’s Scientific Visualization Studio; Blue Marble data courtesy of Reto Stockli (NASA Goddard) The scar’s track through Greenland still shows a measurable heat signature, according to a study published in August 2018. Led by Yasmina M. Martos, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the research team used data previously gathered on Greenland’s magnetic and gravitational profiles to reveal the scar’s location. They also tracked its heat, tracing the scar from northwestern to southeastern Greenland. “It may mean that Greenland can expel its ice faster than we are anticipating in predictive models,” Ivins said. He was part of a science team that recently explored the implications of another hot spot on the opposite side of the planet: A deep mantle plume believed to lie below Marie Byrd Land in West Antarctica. Tracking a hot spot Ivins and JPL researcher Hélène Seroussi, along with others, devised a detailed, three-dimensional computer model of how heat from such a plume might affect the base of the Antarctic ice sheet. A big question: How much heat is too much? In other words, what level of heat from the plume would match changes observed on Antarctica’s surface? The possible plume’s exact size, temperature and location were unknown, despite new seismic imaging information that had begun to improve the picture. And direct measurements of geothermal heat flux from below the ice are extremely rare. But Seroussi and Ivins had the next best thing: satellite and airborne observations of the height of the ice sheet. This fluctuates from place to place as the ice melts from below, causing sudden drops, for instance, when rivers of meltwater at the ice sheet’s base drain rapidly into subglacial lakes downstream. Too much heat from the plume in the computer model would lead to much higher melt-rates than the observations revealed. The model, informed by observations from NASA’s orbiting IceSat satellite, as well as the airborne Operation IceBridge, delivered a solid verdict: while the heat was high beneath Marie Byrd Land, the greatest ice-height variability – and hence the highest heat flow – was located hundreds of kilometers to the west. Here the rates of lake-to-lake water-flows below the ice sheet were also significantly higher. Seismic observations of the area offered further evidence – signs of a rift in Earth’s crust, a great place for heat from the mantle to reach toward the surface. Illustration of lakes and waterways beneath Antarctic ice. Beneath Antarctic ice are systems of lakes (blue dots) and rivers (lines). One recent study found evidence of a heat source called a mantle plume beneath the frozen continent’s Marie Byrd Land. Image credit: NSF/Zina Deretsky. This heat flow is quite subtle, between 150 and 180 milliwatts per square meter. A milliwatt is one thousandth of a watt. Make such a measurement in California’s San Gabriel Mountains, near JPL, and you’ll get readings as high as 60 to 80 milliwatts per square meter. Take the temperature in a place like Yellowstone National Park, known for its high level of geothermal activity, and expect up to 220 milliwatts per square meter over broad regions away from the park’s famous geysers. Subtle as it might be, however, the plume’s “heat flux” could be enough to speed up the melting of the ice sheet. Estimating just how much, and the potential future effects on sea level, will require teasing apart the modest, background heating of the mantle plume – acting over tens of millions of years – from the more powerful, short-term effect of a warming ocean. “It can impact the properties of the ice, but the changes still have to be triggered by something else,” Seroussi, the lead author of the 2017 modeling study, said of the under-ice mantle plume. Such plumes “have been there forever, will be there forever. The ice changes slowly; these things change even slower than the time-scale of the ice. They’ve been there a very long time.”

RELATED BLOG FROM THE UNIVERSITY OF OSLO: HOTSPOT VOLCANISM ON GREENLAND

Hotspot volcanism on Greenland – A corridor in the North Atlantic forms volcanic landscape
Volcanic activity primarily focuses at plate boundaries on Earth. But volcanoes can also form far away from plate boundaries due to plumes of hot material rising from the Earth’s deep interior. Eventually this material reaches the surface and breaks through the Earth’s crust to form a volcano – a so-called “hotspot”. Scientists now present a theory of how this type of hotspot activity can explain massive, past volcanic eruptions in Greenland and in the North Atlantic.

Greenland is the largest island on Earth. In central Greenland researchers have located a corridor with thinned-out landmasses running from east to west, which they explain by Greenland drifting over a stationary hotspot. The thin lithosphere assisted volcanic activities across Greenland 60 million years ago. Illustration photo: Colourbox.no
Greenland is the largest island on Earth. In central Greenland researchers have located a corridor with thinned-out landmasses running from east to west, which they explain by Greenland drifting over a stationary hotspot. The thin lithosphere assisted volcanic activities across Greenland 60 million years ago. Illustration photo: Colourbox.no

In Nature Geoscience, a group of researchers present a new theory and model of processes leading to volcanic activities on both sides of Greenland and in the North Atlantic region that started simultaneously at around 60 million years ago.

As lithospheric plates (the outer shell of our planet) move across a hotspot, volcanic island chains form. One of the most famous chains is the string of volcanoes on the seafloor that connect to Hawaii in the Pacific. Across in the Atlantic Ocean, Iceland is also a well-known site of active volcanism today that is related to a deep hot upwelling (a plume) but a similar string of volcanoes had not been previously found.

However, on Greenland and across the North Atlantic region there are vast amounts of extinct volcanoes that erupted around 60 million years ago. These volcanoes are not arranged in chains but instead are distributed over a large area, so they do not intuitively appear as traditional hotspot volcanism.

One of the authors of the article, Professor Trond H Torsvik (CEED, University of Oslo), says:

“It has remained an open question whether this widespread volcanism was caused by the Iceland plume as a single source. To address this we combined recent results from plate reconstructions, seismic tomography and geodynamic modelling to assess where the plume impacted and how and where plume material could have flowed beneath the lithosphere so as to give rise to the observed volcanism”.

However, the interdisciplinary group of scientists from Germany, Ireland, Canada and Norway demonstrate that these volcanoes can also explained by hotspot activity.

The research team, led by Bernhard Steinberger (GFZ and CEED), used high-resolution tomographic images – a technique to image Earth’s interior structure based on earthquake data – to locate a thinned-out corridor within the Earth’s lithosphere (Figure 1). The corridor they found stretches from east to west across central Greenland.
This feature may have been formed when Greenland moved westwards 90 to 60 million years ago over and across the Iceland plume (hotspot) that is still active within the Earth’s interior.

Figure 1 Greenland moved westward (red arrows) over an active and near stationary Iceland plume between 90 and 60 million years ago (Ma) which resulted in an east–west corridor of thinned lithosphere across Central Greenland (panel a). Perhaps because of stronger plume activity from ~60 Ma, hot material sourced by the Iceland plume broke through the Earth’s crust and simultaneous volcanic activity is observed on either side of Greenland (dated volcanic locations at that time shown as red-shaded circles in panel b). The Iceland Plume was centred beneath eastern Greenland (yellow star in panel b) at 60 Ma and some plume-related magma had been dragged more than 1000 km at the base of the moving lithosphere to remain near the western margin of Greenland, but some magma also travelled SSW along the eastern coast of Greenland and toward Scotland and Ireland. Panel a graphics by Alisha Steinberger.
The research team reconstructed the activity of the Iceland Plume with high precision for the past 90 million years, but:

“After reconstructing the activity of the Iceland plume we were still looking for an explanation why, if the hotspot was already active 90 million years ago in the west of Greenland, volcanic activity only started about 60 million years ago.” explains Steinberger.

With a new model the scientists were able to reconstruct how hot material rising from the plume accumulated within the corridor. They found that the hot material caused the Earth’s lithosphere to be thinned out gradually, starting 90 million years ago (Ma).

Steinberger continues: “We surmise that the accumulation and flow of hot material in the Earth interior, together with the process of plates drifting apart towards East and West, caused the originally thick lithosphere to thin out over the course of millions of years. These geological processes eventually led to the eruption of volcanoes started 60 million years ago and their arrangement at both ends of the landmass”.

What is today known as the Iceland Plume was earlier centred beneath eastern Greenland at 60 Ma (Figure 1) and magma must have propagated horizontally more than 1000 km at the base of the thinned lithospheric corridor across central Greenland.

At the same time, magma also flowed southwards towards the British Isles, within an area that had undergone extensive continental stretching for several hundred million years.

“Iceland plume material flowed to the most thinned rifted lithosphere, and eventually also triggered continental breakup between Greenland and Eurasia (Norway) around 55 Ma because of upside-down drainage of the plume head”, explains Trond H. Torsvik.

Original study: Steinberger, B., Bredow, E., Lebedev, S., Schaeffer, A., Torsvik, T.H. 2018. Widespread volcanism in the Greenland-North Atlantic region explained by the Iceland plume. Nature Geoscience

GEOTHERMAL HOT POOLS IN ICELAND