Photo: Mathilde Bellenger Archives Agence France-Presse
Billions of tons of water from the melting ice may weaken the ocean currents.
The melting of the ice caps of Greenland and Antarctica, in addition to increasing the level of the oceans, could also multiply events, extreme weather, and destabilize the climate of certain regions in the coming decades, warn researchers.
According to the study published Wednesday in Nature, billions of tons of water from the melting ice, especially in Greenland, are likely to weaken the ocean currents that now carry the cold water to the south, plunging down to the bottom of the Atlantic while pushing the tropical waters to the north closer to the surface.
Known by the acronym AMOC (meridional overturning circulation of the Atlantic), this great ocean “conveyor belt” plays a crucial role in the climate system and helps to maintain a degree of warmth on the northern hemisphere.
“According to our models, the melted ice will cause significant disruptions in the ocean currents and change the levels of warming across the globe,” says lead author Nicholas Golledge, from the Centre of antarctic research at Victoria University of Wellington, New Zealand.
Many studies on the ice caps have focused on the speed of the melting of the ice caps under the effect of global warming, and on their “tipping point” (from which temperature rise, their demise will be inevitable, even if the total melting could take centuries).
But less about how these melt water may affect the climate itself.
“The large-scale changes that we see in our simulations are conducive to a climate more chaotic, with events, extreme weather, heat waves more frequent and more intense,” says AFP Natalya Gomez of the university of McGill in Canada.
15 cm by 2100 ?
According to the researchers, by the middle of this century, ” the melt water from the icecap of Greenland will affect significantly the AMOC “, which is already showing signs of slowing down.
It is a “maturity much shorter than expected,” commented Helene Seroussi, California Institute of technology (Caltech), who was not involved in the study.
The researchers ‘ conclusions are based on simulations with the detailed and satellite observations of changes in ice caps since 2010.
Among the likely consequences of the weakening of the atlantic current, the temperature of the air will be higher in the high Arctic, eastern Canada and central America, and on the contrary lower on the Western Europe.
The ice caps of Antarctica and Greenland, which can reach up to 3 km thick, contain more than two-thirds of the freshwater resources of the planet, sufficiently to cause a rising of the oceans, respectively of 58 and 7 meters, if they melted completely.
In another study published Wednesday in Nature, some of the same scientists unveil new projections on the contribution of the melting of the Antarctic increase in sea level by 2100, a subject much debated in the climate community.
A controversial paper 2016 suggested that the cliffs of ice on the continent could collapse and cause a metre rise in oceans by the end of the century, resulting in the displacement of tens of millions of people around the world, particularly around deltas of Asia and Africa.
“We have re-analyzed the data and concluded that this is not the case,” said the lead author Tamsin Edwards, King’s College London.
According to her, the two new studies predict that the Antarctic would “most probably” an increase of 15 cm by 2100, with a maximum limit of about 40 cm.
The group of climate experts of the Ipcc is required to publish by September a report was expected on the rising levels of the oceans. Its latest assessment on the subject in 2013 did not take into account the ice caps, due to a lack of data.