Study: Major Greenland melting could be disaster for Africa’s crops

As Greenland glaciers continue to melt, we have more than the rising seas to worry about, scientists say. A new study suggests that if it gets large enough, the influx of freshwater from the melting ice sheet could disrupt the flow of a major Atlantic current system, which in turn could dry out Africa’s Sahel, a narrow region of land stretching from Mauritania in the west to Sudan in the east.

The consequence could be devastating agricultural losses as its climate shifts in the future. And in the most severe possible scenarios, tens of millions of people could be forced to migrate from the area.

“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 climatic change,” said Christopher Taylor, a meteorologist at the Centre for Ecology and Hydrology in the United Kingdom and an expert on the West African climate, who was not involved with the new research.

The alarming study, published Monday in the journal Proceedings of the National Academy of Sciences, uses a climate change model to investigate the influence of different amounts of ice loss from Greenland, corresponding to different amounts of global sea-level rise, on the western Sahel’s climate system. Prior studies have suggested that this region may be particularly vulnerable to climatic changes produced by disruptions in the ocean.

The idea is that large volumes of meltwater from Greenland have the potential to slow down a major system of ocean currents known as the Atlantic Meridional Overturning Circulation, or AMOC. Experts have described it as a kind of giant conveyor belt, which carries warm water from the equator to the Arctic and cooler water back down south. This transport of heat influences atmospheric processes and helps regulate climate and weather throughout the Atlantic region.

As glaciers in Greenland melt, scientists think that the influx of cold, fresh water could disturb this conveyor belt, causing it to slow down. The resulting disruption in the transfer of heat could cause changes in atmospheric patterns throughout the Atlantic and alter weather patterns around the world. In fact, previous modeling studies indicate that ancient periods of ice melt may have caused the West African climate to become drier.

The researchers were interested in finding out if this might happen again.

To investigate, they assumed a business-as-usual emissions trajectory, which suggests high levels of future global warming and an unclear amount of sea level rise and Greenland melt. The authors modeled scenarios ranging from 1.6 feet to 9.8 feet of sea-level rise.

The model suggested that an influx of freshwater from Greenland does, indeed, slow the AMOC, with greater amounts of sea-level rise corresponding to greater effects on the current’s flow throughout the century. And this slowdown has major consequences for western Africa. With 3.3 feet or more of sea-level rise, the result is an immediate and significant decrease in precipitation in the western Sahel, with up to a 30 percent reduction in rainfall between the years 2030 and 2060. At the same time, temperatures in the region are expected to rise as a result of the continued progression of climate change.

These combined changes have potentially grave consequences for agriculture, the researchers suggest. As temperatures rise, many crops will require more and more water to survive, and a reduction in precipitation could be devastating.