Continued Climate Change May Disrupt Ocean Currents
Climate change is giving us more to worry about than just rising seas, scientists claim. Greenland’s glaciers are melting fast, pouring ice into the Arctic Ocean – and according to a new study, this influx of freshwater from the melting ice could lead to a disruption of a major ocean current system.
The consequence of this disruption could be devastating, drying out the narrow section of land from Mauritania to Sudan – Africa’s Sahel. Climate shifts in the area may bring significant agricultural losses, scientists advise, and a more severe scenario would see the forced migration of tens of millions of people.
“The implications, when expressed in terms of vulnerability of the population in the region are really dramatic and bring home just how sensitive livelihoods are in this region to climate change,” said meteorologist Christopher Taylor, an expert on the West African climate.
Published in the journal Proceedings of the Natural Academy of Sciences, the new study focused on the influence of ice loss from Greenland. Using a climate change model, researchers examined different amounts of global sea level rise and corresponding effects on the climate system of the western Sahel – an area indicated in previous studies as particularly vulnerable to climatic changes due to oceanic disruptions.
Described as a “giant conveyor belt,” the Atlantic Meridional Overturning Circulation (AMOC) carries warm water all the way from the equator up to the Arctic, while pushing cooler water back down south. The transfer of heat generated by this current helps regulate climates throughout the Atlantic region.
However, this conveyor belt could be slowed down by an increase in cold, fresh water from Greenland’s melting glaciers – resulting in changes to atmospheric and weather patterns throughout the Atlantic and around the world.
“It is well-established by now from past meltwater events in Earth’s history that such events have had major impacts on tropical precipitation, and the physical mechanisms for that are basically understood,” said ocean physics expert Stefan Rahmstorf.
The study modeled scenarios ranging from a half a meter to three meters of sea level rise, which lead author Dimitri Defrance with the Institute Pierre Simon Laplace in France said was included as an “extreme” scenario. Still, climate scientists estimate that in a high-emissions scenario, a rise of one or two meters through the end of the century is possible.
Under a meter or more of sea level rise, the model indicated an immediate and significant decrease in precipitation in the western Sahel – up to a 30 per cent reduction in rainfall between 2030 and 2060 – while temperatures continue to rise due to global warming. Combined, these changes could seriously limit agricultural productivity in the area.
With a focus on the region’s two staple crops, millet and sorghum, researchers projected that the land fit for cultivation within the Sahel could drop by more than 400,000 square miles. Tens or even hundreds of millions of people could be affected by these losses.
“The solution is migration or adaptation,” said Defrance, adding that it is possible that less water-intensive crops could be introduced to make up for some of the losses – but a more likely scenario would see many people forced to relocate.
Since the study relies on the continued progression of climate change, these conclusions are not a certainty. Many nations have agreed to reduce greenhouse gas emissions through the terms of the Paris climate agreement, which could force significantly different results through this model.
However, since the AMOC influences the climate and weather in Western Europe and the east coast of North America, as well as throughout the Atlantic, it’s important for scientists to examine what potential impacts could be.
“The climate change induced by the ice sheet melting is around the world,” said Defrance.