New research from CAGE/UiT in Nature Communications show that the immense ice sheet that covered Europe during the last ice age excavated the bedrock equivalent of more than 500 Mt Everests. This extreme glacial erosion profoundly sculpted the landscape we live, work and play in, with incredible impacts on the mountains, lakes, rivers, coasts, soils, mineral and carbon deposits. It even realized many of the geohazards latent across Scandinavia and Europe today.
Text: Mariana Esteves
During the last ice age, the Eurasian Ice Sheet was immense – the third largest on Earth spanning over 5,500 km from temperate conditions in southern Britain to the frigid polar regions of Svalbard and Siberia. Until now, the influence of this ice on Europe’s landscape has not been fully realized, but a new study led by Dr Henry Patton and published in Nature Communications, brings a brand-new perspective on the erosive impact of this great ice sheet that covered Northwest Europe and parts of Asia during the last glacial.
“This study applies a transient model constrained by real-world observations to reconstruct the evolving erosional signature of the Eurasian Ice Sheet through the last 100,000 year-long ice age, revealing how it profoundly sculpted but also protected the landscape visible today.” Says Dr Henry Patton, who conducted this research at CAGE/UiT.
The erosional footprint of the Eurasian Ice Sheet
Using multiple strands of geophysical evidence to train a new model of the Eurasian Ice Sheet, Dr Patton and co-authors reveal 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: 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 almost 3,000 m thick in places and thus had a pronounced impact on the landscape through its erosional footprint. Yet, results from this study show that while there has been focused extreme erosion in some areas like the glacial fjords of Western Norway and in the Barents Sea, there were also large swathes of the landscape – like the high elevation plateaus of Sweden and Norway – that the ice hardly affected at all.
Erosion rates impacted by the climate
Much like in Greenland and Antarctica today, the study finds a close link between climate and ice sheet erosion. It shows that a series of rapid ice sheet fluctuations where rates of erosion increased by almost 1 cm per year occurred on incredibly short, decadal, timescales. These brief “bursts of intense erosion” occurred during periods of abrupt warming, such as around 15,000 years ago at the end of the last ice age – when rising temperatures destabilised remaining ice cover over Eurasia.
The rapidly melting ice during these phases vastly increased the meltwater reaching the bed of the ice sheet, forming vast networks of subglacial rivers and promoting faster ice flow that worked to excavate the bedrock and sediments. These meltwater rivers also transported these eroded sediments from beneath the ice sheet and into the adjoining oceans and fjords, creating an ideal environment for algal blooms to flourish and becoming a major marine carbon sink.
“At its peak melting, the Eurasian ice sheet was discharging sediment volumes equivalent to that found in all rivers globally today. These new modelling results really illustrate not only how ice sheets can respond rapidly to environmental changes over decadal to centennial timescales, but also the huge knock-on effects for many other Earth systems beyond the ice sheet margins.” Says Patton.
The study and results are also relevant to what is going on in Greenland today. Professor Alun Hubbard, co-author of the study says:
“Over the last two decades, Greenland has been losing its vast terrestrial ice reservoir – sufficient to raise global sea-levels by over 7 metres – even faster than the great ice sheets retreated at the end of the last ice age. Greenland’s current deglaciation and locked in commitment to sea-level is the single largest threat to the billion people who live in vulnerable, low-lying regions of the planet. We must act now to curtail carbon emissions and rising temperatures.”
But every cloud has a silver-lining. The quantities of sediments and nutrients washed out by Greenland’s meltwater in plumes, is also sustaining incredible levels of marine-productivity – a boon for the local fishing industry, who are now experiencing record export levels to international markets.
Areas with increased erosion pose a geohazard problem
The impressive glacial imprint in the landscape, for example along Norwegians coasts, has been sculpted over many ice-age cycles, with deep fjords and submarine troughs carved by repeated ice sheet advances. However, a legacy of this intense erosion and deep freezing of mountain landscapes are the inherently over steepened and unstable slopes left behind after deglaciation. Failure of these mountain slopes poses a significant geohazard to many communities across formerly glaciated landscapes around the globe, particularly now as temperatures rise and the permafrost and ice binding these cliffs together thaws.
“By untangling the erosional signature of these past ice sheets we are moving a step closer in being able to understand the long-term processes that affect the landscapes around us today. One important aspect is on the stability of these eroded mountain slopes, which for many around the world still pose a real threat even thousands of years after the last glaciers melted away.” Says Patton.