The Greenland Ice Sheet - Not Just a Victim, but Also Part of a Cure for Global Warming
Minik Rosing
Globe Institute, University of Copenhagen, Denmark Winning
“Vast natural nutrient reserves in the Arctic can secure food for all and significantly reduce atmospheric Greenhouse gas concentrations”
The concentrations of greenhouse gasses in Earth’s atmosphere have reached levels where reduction of emissions can no longer prevent more than 2 °C increase in global temperature within this century. We will need to remove carbon dioxide (CO2) from the atmosphere on a scale of multiple gigatons of CO2 per year to achieve this goal. This has never been done before. To do it, rapidly, we will need to implement scalable solutions with low technological complexity and low demand for critical resources, able to be applied across the globe.
Climate change coupled with a growing world population has put a pressure on food security, making increased agricultural output imperative for the decades ahead. The biodiversity of Earth’s natural ecosystems is under severe pressure. But food production must be increased and at the same time the area of cultivated land must be reduced. To resolve this tension, we will need a significant increase in crop yield per unit of land area.
Since the evolution of photosynthesis 3.7 billion years ago, Earth’s climate has been stabilized by life. Metabolic processes control the composition of the ocean, the atmosphere, and even the rocky crust. Most plant nutrients derive from minerals, and their supply determines how much solar energy life can harvest and use to produce biomass. Minerals formed at high temperatures deep in Earth’s crust react with water and CO2 when exposed to the surface environment and break down in what is called rock weathering. This rock weathering consumes CO2 directly from the atmosphere and releases nutrients to plants, fungi, and other organism which supports additional CO2 uptake by enhanced plant growth.
So, primary productivity, the rate of biomass production, and the consumption of atmospheric CO2, are linked through a common dependency on nutrient release from minerals. Earth’s ecosystems transport hundreds of gigatons of CO2 from the atmosphere, through all things living, and back to the air, into the ocean or into solid rocks. Stimulating this natural system is our best hope of reaching the very high levels of reduction in atmospheric carbon needed to stay within healthy planetary boundaries.
We propose a simple, scalable method to enhance the rate of rock weathering by adding naturally occurring rock flour from Greenland to agricultural soils in warmer climates.
Rock flour is produced when glaciers mill the rocks they cover, into a very fine powder. It consists of mineral grains only 2-3 thousand of a millimeter across. The Greenland Ice Sheet exports 1 gigaton (Gt) of rock flour to the coast annually, and Gt scale deposits formed during the past 8,000 years are widespread. Due to an extremely fine grain size of the glacial rock flour, the surface area is enormous. 25 megatons (Mt) of rock flour provide a reactive mineral surface area equal to total surface area of Earth. The weathering process that regulates atmospheric CO2 levels on geologic million-year time scales, can be accelerated to work on a timescale of years - relevant to society in real time - by exposing the vast silicate mineral surface area of the glacial rock flour to soils on a global scale.
Importantly, there are no competing requests for this resource, it is inactive in the cold Arctic environment, it can be extracted with a minimum of infrastructure build up and can be implemented immediately.
Extensive field trials in Denmark and Ghana have demonstrated increases in crop yield of 20-50% and a potential CO2 uptake through weathering reactions of 250 kg per ton of rock flour applied.
In our work (Dietzen and Rosing, 2023), we have derived relations between soil acidity level and the efficacy of CO2 uptake, that help quantify the effects of enhanced rock weathering in soils. They demonstrate a simple yet scientifically rigorous, conservative method to quantify carbon uptake based on soil sample analysis. This can help the identification of the best target soils for enhanced rock weathering application, and can be used in protocols for monitoring, reporting, and verifying carbon uptake and enable more accurate accounting of carbon budgets in agricultural systems.
There is a rapidly growing research effort on enhanced rock weathering as a negative CO2 emission strategy, mostly focusing on basalt or olivine as the reactive rock substrate. The application of these silicate materials is dependent on mining and crushing of solid rocks to provide the necessary fresh surface area. This is associated with high consumption of energy for the mining and crushing processes, and environmental risks in relation to mining and release of environmentally problematic metals from the minerals during weathering. Application of glacial rock flour will be able to increase the mineral reactive surface area of Earth’s surface environment significantly, without the need for mining or crushing. The vast Greenland Ice Sheet integrates rocks from very large regions of Greenland’s mountains. Thus, the chemical composition of glacial rock flour is similar to the granite that formed Earth’s continents where crop plants evolved. The rock flour has no elevated levels of environmentally problematic elements. Conversely, plant nutrients are abundant in the material and allow for the dual purpose of increased crop yield and CO2 sequestration when used as a soil amendment in agricultural practice, especially in the tropics and sub-tropics, where crop yield increase is most urgent.
The rate of climate change is greater in the Arctic compared to any other regions of Earth. The Arctic has been portrayed as a victim and symbol of the human-induced climate crisis. A region which societies are seemingly victims with no agency or influence on the future of their region, let alone of our planet in general. We should change this perspective and include the Arctic as part of any solution to global problems. We would therefore like to see the release of the vast potential of Greenland’s glacial rock flour resource, as a significant part of the solution for the climate, biodiversity, and food security crises, as well as an agent for positive development for the Arctic region and its peoples.
Photo 1. Dried rock flour surface, Nuuk, West Greenland.
Photo 2. A 1 gram cube of granite has a surface area of 3 cm2. The 1 gram of rock flour on the right has a surface area of 200,000 cm2. Liquorice allsort for scale.
Photo 3. Test plots from University of Ghana field trial under supervision of Dr. Eric Oppong Danso. The plot to the left has received no glacial rock flour and the plot to the right has received the equivalent to 20 t/ha glacial rock flour. Photo. E. Oppong Danso, University of Ghana.
Photo 4. Christiana Dietzen and Minik Rosing at Globe Institute, University of Copenhagen. Credit: © GottschauMedia.
