Mapping heat flow below Greenland highlights geothermal ‘deviation zone’

Mapping heat flow under Greenland highlights

Spatial map depicting average geothermal flow in and around Greenland drawn from machine learning results. Thermal anomalies appear off the coast of the metropolitan area in the southwest, which could be interesting in terms of geothermal energy harvesting. Overall, though, the heat flow from below Greenland is lower than previously expected. Credit: Colgan Wansing, 2022

In our understanding of global geothermal flow, Greenland and the surrounding ocean floor have effectively been a blind spot. Now, scientists have extracted all available and somewhat unavailable heat flow data, creating a common ground for working with Greenland’s geothermal as an alternative energy source, a factor in ice sheet melt and much more.

As it turned out, the land under Greenland is colder than previously thought. This is one of the conclusions of a research paper just published in Earth system science data by an international team of scientists led by the Geological Survey of Denmark and Greenland (GEUS).

Researchers have compiled a new database and Heat flow A model consisting of all available geothermal flow data for the area. This involved a great deal of research in the “gray literature,” or observations not previously included in the scarce data in Arctic heat flow models. The researchers used this monitoring database to create a new spatial map of heat flow in and around Greenland.

The new heat flow model, created using machine learning, shows that the average heat flux on Earth is 44 MW/m²2 (milliwatts, that is, one thousandth of a watt, per square metre). It is much lower than previous models estimated. These models rely on significantly less data than those recently published, in which 129 new measurements were included for a total of 419 measurements. For some previous heat flow models, the average geothermal flux per unit was several times that of a newly published estimate.

geothermal hotspots

Although the average heat flux through Greenland was cooler than previously estimated, the heat flux inland coastal areas The one that appeared “recently” from the ocean was actually much warmer than expected. This might be good news for the residents here.

“In fact, this area along the west coast of Greenland has three times the heat inflow from the interior, so it makes sense to investigate the possibility of harvesting geothermal energy to the communities out there,” says lead author and chief scientist William Colgan of GEUS’s Department of Glaciology and Climate.

Mapping heat flow under Greenland highlights

Overview of locations and types of locations in the heat flow measurement database. Yellow dots indicate locations where we reassess heat flux values ​​presented in the 2018 International Heat flux panel or other studies. The dashed line indicates the boundaries of our study, 500 km off the coast of Greenland. The Meighen and Barnes ice caps are outside of these limits, but we are still reporting such subglacial measurements here. Credit: . Credit: Colgan Wansing, 2022

dynamic area

According to William Colgan, this shows how much we don’t know about the area.

“This region is a rather peculiar geothermal region for sure. You have the really old and stable North Atlantic Craton in southern Greenland, which is very picturesque, and right next door is the Mid-Atlantic mountain range and Iceland with all its volcanic activity. Not to mention the ice cover effect. Weird in terms of geothermal heat, which is really a little different from the rest of the world. Thus, it is important to understand.”

He adds that a geothermal flow that appears to be lower than expected does not alter the rate at which the ice sheet is melting. Much of today’s melt reflects recent warming of the glacial atmosphere and glacial ocean boundaries. Geothermal flux at the glacial lithosphere boundary does not change rapidly, but is important for understanding the stability of the ice sheet at the ice-sheet interface.

‘May the ocean do too’

Initially, William Colgan and colleagues became interested in geothermal flow because of its role in the dynamics of ice sheet melt. Looking up heat flow data from the Greenland region, it soon became apparent that this is a somewhat underdeveloped region. Or at least disorganized.

“There are really a bunch of different players collecting geothermal flow data in and around Greenland through time, but all with individual uses. Like, oil and gas companies have collected some data to help locate pockets of gas and oil underground. There are also permafrost and glaciers. who use heat flux as an important limit condition in their models. Most or less everyone in the Earth sciences uses heat flux in some sense, but no one has clearly felt the need to compile a comprehensive overview yet, I think.”

Mapping heat flow under Greenland highlights

An example of a well providing heat flow data in Greenland drilled off the ice sheet near point 660 with the background of the Isunnguata Sermia glacier outlet. Credit: Lillemor Claesson Liljedahl

While trying to locate good sites to retrieve new geothermal flow data, William Colgan and colleagues had to figure out where the data was actually being collected. The more they talked with researchers from other research fields, the more untapped data was revealed.

“At first we were just looking at sub-glacial heat flow data, then we got in on data from the subaerial regions, or the tundra, and eventually we thought ‘okay, we can also do the oceans’ and cover the whole area,” he says.

16 institutions, eight countries

Thus, it has turned into an endeavor to expand from the original team of glaciologists at GEUS to a group of researchers from various disciplines located at 16 institutions in eight different countries. A joint effort resulted in the new geothermal heat flow model being the first to include all available marine and terrestrial data, including below the ice sheet, in Greenland.

Of course, even with 419 data points now recorded for the region, the data coverage is still very small for an area as large as Greenland. Greenland has a variety of geological provinces and physical processes That contribute to large spatial differences in heat flow, as second author and PhD researcher at the Institute of Earth Sciences at Kiel University points out, Agnes Wansing:

‘Particularly for the interior of Greenland only a few data points Exists and how they are treated machine learning It can significantly change the prediction of the model. “

To enhance data coverage, the team is currently looking into the possibility of acquiring a thermal probe to bring down the back of research ships doing field work in the Arctic.

“Then we can continue to fill in the map, which still looks rather scarce,” says the lead author.

New model predicts more accurately how massive glaciers will melt

more information:
William Colgan et al., Greenland Geothermal Heat Flow Database and Map (Version 1), Earth system science data (2022). DOI: 10.5194/essd-14-2209-2022

The on-site measurement database and grid heat flow model, as well as other supporting materials are freely available from the GEUS Dataverse. doi: 10.22008/fk2/f9p03l

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