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Glaciers around the world are melting faster than ever

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Maria Gill
Maria Gill
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Glaciers are melting all over the world under the influence of global warming caused by human activity. However, the extent of the phenomenon remained to be clarified. Today, researchers claim that they are losing nearly 300 billion tons of ice every year. And that the rate of this melt has obviously accelerated over the past twenty years. Significant participation in sea level rise.

for the first time, CNRS ResearchersWith support from the National Center for Space Studies (Cnes), I was able to accurately measure changes in everyone’s thickness Glaciers of the world Or let’s say exactly 97% of them. And their conclusions are not encouraging. Wherever he is on the planet, or almost Glaciers It is now melt at a record, accelerating pace. Under the influence of anthropogenic greenhouse.

Between 2000 and 2004, the world’s glaciers lost about 227 billion tons every year. Between 2015 and 2019, they melted from about 298 One billion tons of ice every year. In other words, while in 2000 the glaciers decreased by 36 cm, they lost at least 69 cm in 2019. Mass Meanwhile, the world has decreased by an average of 267 billion tons per year since 2000. This is more than the Greenland or Antarctic ice sheet. This is enough to pour 50 cm of water over the entire territory of France.

These values ​​were taken by the researchers from analyzing half a million pictures they took Earth’s moon Approximately 220,000 glaciers. Thanks to two cameras, since 2000 I have regularly obtained pairs of images of the Earth’s surface. And these pictures allowed the scientists to get creative Digital forms From the height of ice with unparalleled spatial and temporal resolution.

Melting glaciers raise sea levels

For glaciologists all over the world, this act is literally a game-changer. Because only a few hundred glaciers are monitored On site. This new data should allow researchers to better constrain their models. To better assess the interaction between the weather And glaciers. They have already noticed that while the ten-year changes are in Fall out Explain some Anomalies Observed regionally – in Scandinavia, for example – the global acceleration of glacier mass loss clearly reflects Global warming of the atmosphere.

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Researchers also expect to better predict, in particular, what the contribution of glaciers to a rise will be sea ​​level. This phenomenon is often attributed to Source The ice in Greenland and Antarctica also appears to be “significantly” related to melting glaciers.

If all of the melted ice since 2000 reached the ocean, the researchers calculate that it has already raised the water level by 0.74 mm per year. They also estimate that between 6 and 19% of the acceleration of sea level rise in the 21st centurye The century is due to the loss of mass from the glaciers. 21% of this rise comes from glacial meltwater. According to the study authors, “ Scientifically rigorous evidence of the urgency of rapid teamwork Reducing greenhouse gas emissions ».

Melting glaciers are the main cause of rising ocean levels

The world’s melting glaciers will play a major role in raising the ocean level, much more than that breadth Thermal water or melting ice in Greenland and Antarctica. The increase in water levels due to this phenomenon between 1902 and 2009 was estimated at 11 cm. This number can increase an additional 15 cm in 2100.

Article by Quentin Muguet published on 11/19/2012

The Means the level of the ocean It continues to rise since the beginning of XXe century. The total increase for this period is currently estimated at 20 cm. There are two factors related to the warming of our planet that could explain this. On the other hand, the increase in temperatures causes A. Thermal expansion Of water and thus an increase in Four volumeV. On the other hand, the the heat It melts ice cream, whatever its origins. status Arctic ice raft The news struck last summer but let’s not forget those large amounts offresh water They are also trapped inside glaciers.

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I am a mercenary And colleagues fromUniversity of Innsbruck (Austria) determined its participation in the average elevation level Oceans During the last century. They modeled nearly 300,000 glaciers Door Our planet, except for Greenland and Antarctica. Then their development was tracked over time, taking into account precipitation and Temperatures Carefully recorded for many years. The results provided by the simulations were then validated with thousands of measurements taken in the field.

Thus, from 1902 to 2009, he was Melting glaciers It would have caused the average sea to rise by 114 ± 5 ​​mm, or about 11 cm. So it will be the main reason why water levels rise, even before the Antarctic and Greenland ice sheets melted and thermal expansion! This finding was published in the journal Cryosphere.

Half of the snow in the Alps in 2040

Surprisingly, the overall rate of solubility during XXe The horn would have been relatively steady, despite the temperature changes. In fact, in periods of cold, the Glaciers Get bigger, go down and stop in warmer regions where … it is melting. Additionally, the turn of the century, which was much cooler than it is today, was marked by two relatively warm periods in North Pole (In the thirties and fifties of the last century). Then they caused a major melt of the Canadian glaciers.

Projections have also been made to determine the effect of melting glaciers on average sea levels by 2040, 2100 and 2300. To do so, 15 Climate models Belongs to Associated Model Comparison Project, Phase 5 (CMIP5) to estimate the potential evolution of temperature and precipitation in the coming centuries. For each of them, four possible scenarios for technical, economic and social developments in our company have been launched (RCP 2.6, 4.5, 6.0 and 8.5). In particular, they make it possible to estimate quantities Greenhouse gases That we will issue.

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The AlpLike all regions with small glaciers, it could lose half of its ice by 2040, but without much impact on it. Oceans From the globe (height 0.2 mm). The situation is completely different for countries with large bodies of frozen water. Thus, Canada will maintain 70% of the volume of arctic glaciers by the year 2100, but in the meantime, thawed parts will lead to a sea level rise of 2 cm!

Globally, the average ocean level could rise from 148 ± 35 mm (RCP 2.6) to 217 ± 47 mm (RCP 8.5) by the end of the century. In 2300 the height must be at least 248 ± 66 mm (RCP 2.6), the maximum is set at 424 ± 46 mm (RCP 8.5). Of course, all of these numbers do not take into account the Greenland ice melt Antarctica and the thermal expansion of water, remain subject to many uncertainties. For information, RCP 2.6 corresponds to a very optimistic scenario where humans can quickly stop CO production2 Then to absorb it.

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