Scientists analyzing geological samples from Scotland’s Ethan Estuary have found that melting ice sheets was likely the trigger for a major climate change event just over 8,000 years ago.
The research, carried out by a joint team of geoscientists from four Yorkshire universities, under the direction of Dr Graham Rush from the University of Leeds and Leeds Beckett University, explores the current melting of Greenland’s ice. may provide insight into the potential impact that this has on the planet. Global climate patterns.
More than 8,000 years ago, the North Atlantic Ocean and northern Europe experienced significant cooling due to changes in a major ocean current system known as the Atlantic Meridional Overturning Circulation (AMOC).
Changes in AMOC have also affected global rainfall patterns.
It is believed that the influx of large amounts of freshwater into the North Atlantic seawater caused the collapse of the AMOC.
The research team took core samples from sediments in the Ethan Estuary to understand what was happening to the sea surface more than 8,000 years ago.
Analysis of microfossils and sediments in the samples shows that sea-level changes have reached 13 millimeters per year, which is likely to rise by about 2 meters per year due to individual sea-level fluctuations, deviating from the usual background fluctuations of about 2 millimeters per year. It turned out that it did. At the Ethan Estuary.
Analysis of core samples provides further evidence that there were at least two major freshwater sources draining into the North Atlantic Ocean and causing changes in the AMOC, rather than a single source as previously thought. .
The idea held by many scientists was that the fresh water came from Lake Agassiz Ojibway, a huge lake the size of the Black Sea near what is now northern Ontario, and flowed into the ocean.
“We found that while the lake is huge, it is not large enough to account for all the water flowing into the ocean and contributing to the sea level rise that we observed,” said Dr Rush.
Rather, Rush and his colleagues believe that the melting of the Hudson Bay ice saddle that covered much of eastern Canada and the northeastern United States injected vast amounts of water, which is reflected in the core samples.
Ocean circulation disperses heat
Thermal energy drives the world’s climate, and disruptions to ocean currents have had major effects around the world.
Temperatures in the North Atlantic and Europe fell by 1.5 to 5 degrees Celsius, lasting for about 200 years, while other regions experienced above-average warming. Precipitation also increased in Europe, while other parts of the world, such as parts of Africa, became drier and continued to experience long periods of drought.
The study’s authors believe their work provides insight into how the current melting of Greenland’s ice sheet may affect the Earth’s climate system.
Dr Rush added: ‘We know that AMOC is currently slowing down, and although there are still discussions, there are predictions that it may close completely.
“But by looking at past events, we can learn more about the causes and likelihood of these changes. We have shown that rapid bed retreat can lead to a range of significant climate impacts with very worrying consequences.”
Reference: “Magnitude and source of snowmelt forcing for the 8.2 ka climate event constrained by relative sea level data for eastern Scotland” Graham Rush, Ed Garrett, Mark D. Bateman, Grant R. Bigg, Fiona D. Hibbert, David E. Smith and W. Roland Gehrels, August 21, 2023; Quaternary period scientific progress.
DOI: 10.1016/j.qsa.2023.100119