Heat flux mapping beneath Greenland highlights geothermal ‘anomalous zone’

Spatial map illustrating average geothermal heat flux in and around Greenland derived from machine learning results. Heat anomalies are appearing off the coast of the Capital Region in the southwest, which could be of interest for geothermal energy harvesting. In general, however, the heat flux from below Greenland is lower than previous estimates. Credit: Colgan and Wansing, 2022

In our understanding of global geothermal heat flow, Greenland and the surrounding ocean floor have effectively been a blind spot. Now scientists have unearthed all available and somewhat unavailable heat flux data, creating common ground to work with geothermal heat from Greenland as an alternative energy source, a factor in ice sheet melting and much Moreover.

It turns out that the ground beneath Greenland is even colder than previously thought. This is one of the conclusions of an article which has just been published in Earth System Science by an international team of scientists led by the Geological Survey of Denmark and Greenland (GEUS).

The researchers compiled a new database and heat flow model including all available geothermal heat flow data for the region. This involved a large amount of digging into “grey literature” or observations not previously included in rare Arctic heat flux models. The researchers used this observational database to create a new spatial map of heat fluxes in and around Greenland.

The new heat flux model, created with machine learning, shows that the average heat flux on earth is 44 mW/m2 (milli Watt, i.e. one thousandth of a Watt, per square meter). Which is significantly lower than what previous models estimated. These models are based on much less data than the recently released model, in which 129 new measurements are included for a total of 419 measurements. For some of the previous heat flux models, the average geothermal heat flux per unit was several times higher than the recently published estimate.

Hotpots for geothermal energy

Even though the average heat flow through Greenland was colder than expected, the heat flow in coastal areas that “recently” emerged from the ocean was actually much warmer than expected. This may be good news for people here.

“In fact, this area along the west coast of Greenland has three times more heat flux than further inland, so it makes sense to investigate the possibility of harvesting geothermal energy for communities that are there,” says senior author and senior scientist William Colgan of GEUS’ Department of Glaciology and Climate.

Heat flux mapping beneath Greenland highlights geothermal 'anomalous zone'

Overview of locations and site types in the heat flux measurement database. Yellow dots indicate sites where we re-evaluate heat flux values ​​presented in the International Commission on Heat Flux 2018 or other studies. The dotted line indicates the limit of our study, 500 km from the coast of Greenland. The Meighen and Barnes ice caps lie outside this boundary, but we still report these subglacial measurements here. Credit: . Credit: Colgan and Wansing, 2022

A dynamic neighborhood

According to William Colgan, this clearly shows how little we still know about the region.

“This area is a weird geothermal area for sure. You have this very old, stable North Atlantic craton south of Greenland which is pretty cool, and right next to it is the Mid-Atlantic Ridge and Iceland with all its volcanic activity. Not to mention the influence of the ice sheet. All of this creates a strange geothermal region, which is really a bit different from the rest of the world. And therefore, important to understand.”

The geothermal heat flux appearing to be lower than expected does not change the rate at which the ice sheet is melting, he adds. Much of today’s melt reflects recent warming of the ice-atmosphere and ice-ocean boundaries. The geothermal heat flux at the ice-lithosphere boundary does not change rapidly, but is important for understanding the stability of the ice sheet at the ice-bed interface.

“Might as well do the ocean”

Initially, William Colgan and his colleagues became interested in geothermal heat flow because of its role in the dynamics of ice sheet melting. While researching heat flux data from the Greenland region, it quickly became apparent that this was a somewhat underdeveloped region. Or at least disorganized.

“There have actually been a range of different actors who have collected data on geothermal heat flow in and around Greenland over time, but all with individual uses. For example, oil and gas companies have collected data to help locate pockets of gas and oil underground.There are also the fields of permafrost and glaciology that use heat flow as an important boundary condition in their models. world in geoscience uses heat flow in some sense, but obviously no one has felt the need to compile a comprehensive overview until now, I suppose.”

Heat flux mapping beneath Greenland highlights geothermal 'anomalous zone'

Example of a borehole providing heat flux data in Greenland drilled just off the ice cap near point 660 with the Isunnguata Sermia outlet glacier in the background. Credit: Lillemor Claesson Liljedahl

While trying to locate good locations to retrieve new geothermal heat flux data, William Colgan and his colleagues had to discover where the data had previously been collected. The more they talked to researchers from other areas of research, the more untapped data was uncovered.

“At first we were just looking for subglacial heat flux data, then we went into the data for the subaerial, or tundra, areas, and finally we thought ‘well, we might as well do the ocean “and cover the whole region,” he says.

16 institutions, eight countries

Thus, it grew into an enterprise that expanded from the original team of glaciologists at GEUS to a range of researchers from different disciplines located in 16 institutions in eight different countries. A joint effort results in the new geothermal heat flux model which is the first to include all available offshore and onshore data, including under the ice sheet, in Greenland.

Of course, even with 419 data points now recorded for the area, data coverage is still very low for an area as large as Greenland. Greenland has a diversity of geological provinces and physical processes that contribute to substantial spatial variations in heat flux, as Agnes Wansing, second author and doctoral student at the Institute of Geosciences, University of Kiel, points out:

“Especially for the inner part of Greenland, only a few data points exist and how they are processed in machine learning can significantly change the model’s prediction.”

In order to improve data coverage, the team is currently investigating the possibility of acquiring a thermal probe to be placed on the back of research vessels carrying out fieldwork in the Arctic.

“Then we could continue to fill in the map, which still seems quite rare,” explains the lead author.

New model more accurately predicts melting of massive glaciers

More information:
William Colgan et al, Greenland Geothermal Heat Flux Database and Map (Version 1), Earth System Science (2022). DOI: 10.5194/essd-14-2209-2022

The in-situ measurement database and grid heat flux model, along with other supporting documents, are available free of charge from the GEUS Dataverse. DOI: 10.22008/FK2/F9P03L

Provided by the University of Kiel

Quote: Mapping heat flux beneath Greenland highlights geothermal ‘anomalous zone’ (2022, May 13) Retrieved May 14, 2022 from https://phys.org/news/2022-05-beneath-greenland-highlights- geothermal-freak.html

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