The power of ice that sculpted Fennoscandia’s landscape
Such extreme glacial erosion profoundly shaped the landscape that we live, work and play in today, with major impacts on mountains, lakes, rivers, coasts, soils, mineral and carbon deposits. Even realizing the many geohazards – such as landslides and rockfalls - that lie latent across Scandinavia.
There is a lot to learn from examining the past behaviour of the ice sheet that once covered much of the northern hemisphere. During the last ice age, the Eurasian Ice Sheet was the third largest on Earth - spanning over 5,500 km from temperate conditions in southern Britain up across Fennoscandia and reaching the frigid polar regions of Svalbard and Siberia. Until now, the influence of this massive ice sheet on our landscape has not been fully realized, but a new study by researchers Alun Hubbard and Henry Patton of Oulu and Tromso universities published in Nature Communications, brings a brand-new perspective on the full impact of this ice on Northwest Europe and parts of Asia during the last glacial.
“At its peak melting, the Eurasian ice sheet was discharging more sediments than all rivers globally today. Our results illustrate not only how ice sheets can respond abruptly to environmental changes in decades, but also the huge knock-on effects for many of Earth’s other systems that extend well beyond ice sheet margins”, says professor Alun Hubbard at the University of Oulu.
The erosional footprint of the Eurasian Ice Sheet
“This innovative study uses a transient model constrained by multiple lines of real-world observations and measurements to reconstruct the evolving erosional signature of the Eurasian Ice Sheet throughout the entire last ice age, revealing how it profoundly sculpted but also protected the landscape visible today”, Says Dr Henry Patton.
The (literally) ground-breaking research reveals the extreme and complex nature of glacial erosion over the last 100,000 years, providing an invaluable long-term perspective. The efficiency and interplay of environmental and internal controls governing the patterns of erosion are identified in the study. Particularly, the key roles of climate, geology and topography, but also the critical importance of the ice sheet’s thermal and mechanical regime itself.
The Eurasian Ice Sheet was over 3km thick in places and thus had a vast impact eroding the bedrock beneath. Results from this study show that while there was focused extreme erosion in some areas like the glacial fjords of Western Norway and the Barents Sea, in others - such as Finland and Sweden with tougher bedrock - erosion was more moderated but widespread including much of the Baltic, Ostrobothnia and Oulu where the landscape was largely scoured flat leaving 1000s of lakes as well as the moraines. drumlins, eskers, kettle holes and terraces that are the familiar textbook features that we can see around us.
Melt lake on the Greenland Ice Sheet. Photo: Alun Hubbard.
Erosion rates impacted by the climate
At the end of the last ice age 15,000 years ago rising temperatures destabilised remaining ice cover over Eurasia. The melting ice increased the supply of meltwater to the ice sheet bed, forming subglacial rivers that excavated even more bedrock and sediments. Meltwater rivers also efficiently transported eroded sediments from beneath the ice to the adjoining oceans and fjords, creating ideal conditions for marine ecosystems to flourish and forming a major offshore carbon store.
The study is very relevant to Greenland today. Hubbard says: “In the last 20 years, Greenland’s ice sheet - a terrestrial frozen reservoir with enough water to raise global sea-levels by 7+ metres - has been melting even faster than the Eurasian ice sheet at the end of the last ice age. Greenland’s current deglaciation and commitment to sea-level rise is the single largest threat to the half billion people who live in vulnerable, low-lying coasts of the planet. We need to act positively to curtail emissions and rising temperatures.”
But every cloud has a silver-lining says Hubbard. “The huge quantities of sediments and nutrients washed out by Greenland’s meltwater plumes also sustain incredible levels of marine-productivity; a boon for local fishing industry now enjoying record catches and international exports.”
The research article was published in Nature Communications in December 2022.
Research article: Patton, H., Hubbard, A., Heyman, J. et al. The extreme yet transient nature of glacial erosion. Nat Commun 13, 7377 (2022). https://doi.org/10.1038/s41467-022-35072-0