‘If human activities are starting to impact this system, it is a worrying sign that the scale of human impacts on the climate system may be reaching a critical point’
Cold, fresh water from the Greenland Ice Sheet may disrupt a key ocean current in the North Atlantic, scientists said after updating estimates of the freshwater flux based on new satellite data. The study, published in the journal Nature Communications, warns that the changes could have as-yet uncertain implications for the global climate.
At issue is the Atlantic Meridional Overturning Circulation, which transports a large amount of heat into the North Atlantic where it is given up to the atmosphere and helps regulate the climate in Europe and North America.
“We derived a new estimate of recent freshwater flux from Greenland using updated GRACE satellite data,” said University of South Florida professor Tim Dixon. “The data suggest that the influx of freshwater from Greenland is accelerating, and has changed the Labrador Sea in ways that could lead to a weakening of the AMOC.”
The amount of freshwater flux from Greenland was relatively stable from the late 1970’s to the mid 1990’s, and then began to increase.
“Focused freshwater flux into the Labrador Sea has the potential to increase the buoyancy of surface waters and reduce formation of dense, deep water that helps drive the overturning circulation,” said co-author Don Chambers , USF College of Marine Science associate professor.
“The AMOC and Gulf Stream are part of a complex global ocean circulation system that is still not completely understood,” said Dixon. “If human activities are starting to impact this system, it is a worrying sign that the scale of human impacts on the climate system may be reaching a critical point.”
A natural clockwise ocean circulation pattern around Greenland drives most of the fresh water toward the Labrador Sea, magnifying its impact and increasing the possibility of significant effects on the AMOC, said Qian Yang, the paper’s first author and a PhD student at USF whose dissertation, in part, includes this research.
According to the researchers, not only are changes in the AMOC difficult to measure, it’s also difficult to separate natural climatic variation from climate changes induced by human activity.
The potential consequences of a weakened AMOC include changes in climate.
“The AMOC transports a large amount of heat into the North Atlantic where it is given up to the atmosphere and helps regulate the climate in Europe and North America. The major effect of a slowing AMOC is expected to be cooler winters and summers around the North Atlantic, and small regional increases in sea level on the North American coast,” Chambers said.