Graphs showing the Sahelian agro-ecosystem vulnerability to an acceleration of ice-sheet melting during the 21st century. Mechanism: Freshwater flux to Sahel rainfall. From Mulitza, et al., 2008, and Liu, 2014. Graphic: Defrance, et al., 2016 / ResearchGate

By Chelsea Harvey
6 June 2017

(The Washington Post) – As melting Greenland glaciers continue to pour ice into the Arctic Ocean, 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 ocean 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 the area’s climate shifts. And in the most severe 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 Center 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 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. [more]

A climate chain reaction: Major Greenland melting could devastate crops in Africa

ABSTRACT: The acceleration of ice sheet melting has been observed over the last few decades. Recent observations and modeling studies have suggested that the ice sheet contribution to future sea level rise could have been underestimated in the latest Intergovernmental Panel on Climate Change report. The ensuing freshwater discharge coming from ice sheets could have significant impacts on global climate, and especially on the vulnerable tropical areas. During the last glacial/deglacial period, megadrought episodes were observed in the Sahel region at the time of massive iceberg surges, leading to large freshwater discharges. In the future, such episodes have the potential to induce a drastic destabilization of the Sahelian agroecosystem. Using a climate modeling approach, we investigate this issue by superimposing on the Representative Concentration Pathways 8.5 (RCP8.5) baseline experiment a Greenland flash melting scenario corresponding to an additional sea level rise ranging from 0.5 m to 3 m. Our model response to freshwater discharge coming from Greenland melting reveals a significant decrease of the West African monsoon rainfall, leading to changes in agricultural practices. Combined with a strong population increase, described by different demography projections, important human migration flows could be potentially induced. We estimate that, without any adaptation measures, tens to hundreds million people could be forced to leave the Sahel by the end of this century. On top of this quantification, the sea level rise impact over coastal areas has to be superimposed, implying that the Sahel population could be strongly at threat in case of rapid Greenland melting.

    Consequences of rapid ice sheet melting on the Sahelian population vulnerability



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