Scientists have discovered that melting ice 8,000 years ago affected global weather patterns. The study sheds light on the potential impact of Greenland's melting ice on future climate. Scientists analyzing geological samples from the Etam Estuary in Scotland have found that melting ice may have been the trigger for a major climate change event more than 8,000 years ago.
The research was carried out by a collaborative team of geoscientists from four Yorkshire universities, led by Dr Graham Rush, affiliated with the University of Leeds and Leeds Beckett University.
More than 8,000 years ago, the North Atlantic and Northern Europe experienced significant cooling due to changes in a major ocean current system called the Atlantic Meridional Overturning Circulation (AMOC).
Changes in the AMOC also affect global rainfall patterns, and a massive influx of freshwater into the salty waters of the North Atlantic is believed to have caused the AMOC's disintegration.
The research team took core samples from sediments at the mouth of the Etan River to understand how sea levels changed more than 8,000 years ago.
By analyzing microfossils and sediments in the samples, they found that changes in sea level deviated from the normal background fluctuations of about 2 millimeters per year, reaching 13 millimeters per year. Individual sea level events caused the water level in the Etan Estuary to rise by about 2 meters.
Analysis of the core samples provides further evidence that at least two major freshwater sources draining into the North Atlantic are causing changes in the AMOC, rather than a single source as previously thought.
Many scientists believe that the fresh water came from a huge lake, Lake Agassiz-Ojibway, an area the size of the Black Sea near what is now northern Ontario, from which it drained into the ocean.
Dr Rush said: "Our research shows that despite their size, lakes are not large enough to account for all of the water flowing into the ocean causing sea level rise."
Dr. Rush and his colleagues believe that melting of the Hudson Bay ice saddle, which covers eastern Canada and much of the northeastern United States, has injected large amounts of water into the ocean, which is reflected in the core samples.
Heat is the driving force of the world's climate, and disruptions to ocean currents can have significant impacts around the world. Temperatures dropped by 1.5 to 5 degrees Celsius in the North Atlantic and Europe and lasted for about 200 years, and other regions experienced above-average increases. Rainfall has also increased in Europe, while other parts of the world, such as parts of Africa, have experienced drier conditions and prolonged droughts.
The authors of the study believe that this study provides insight into the impact of the melting of the Greenland ice sheet on the global climate system.
Dr Rush added: "We know that the AMOC is currently slowing down and, although this remains controversial, some predictions suggest it could shut down completely. However, by studying past events we can learn more about what is causing these changes and their likelihood. We have shown that, depending on the path of future fossil fuel emissions, possible rapid ice sheet retreat in Greenland would create a range of significant climate impacts, the consequences of which would be very worrying."