Il se passe quelque chose d'étrange au Groenland, et c'est plutôt inquiétant. La glace là-bas est recouverte de taches sombres, et ce n'est pas de la saleté ordinaire—ces choses sont vivantes ! Les scientifiques ont découvert que des algues se répandent sur la glace, et comme elles sont sombres, elles absorbent davantage de lumière solaire. Cela provoque une fonte plus rapide de la glace, ce qui pourrait entraîner une augmentation plus rapide du niveau de la mer. Plus la glace fond, plus les algues se répandent, et cela crée un cycle effrayant. Si cela continue, cela pourrait avoir de grandes répercussions sur le climat de notre planète. Animation créée par Sympa. ---------------------------------------------------------------------------------------- Musique par Epidemic Sound https://www.epidemicsound.com Pour ne rien perdre de Sympa, abonnez-vous!: https://goo.gl/6E4Xna ---------------------------------------------------------------------------------------- Nos réseaux sociaux : Facebook: https://www.facebook.com/sympasympacom/ Instagram: https://www.instagram.com/sympa.officiel/ Stock de fichiers (photos, vidéos et autres): https://www.depositphotos.com https://www.shutterstock.com https://www.eastnews.ru ---------------------------------------------------------------------------------------- Si tu en veux encore plus, fais un tour ici: http://sympa-sympa.com
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00:00These dark spots on the ice cap of Greenland are not simple imperfections.
00:05Every summer, the ice, usually of a bright white color,
00:09turns gray in some areas.
00:11This dark area, which remained a mystery for a long time,
00:14revealed its secret when it was discovered that this strange transformation
00:18was due to the appearance of algae with red, green and brown shades.
00:22What is particularly worrying is that this algae proliferation does not stop growing.
00:28The dark area darkens more,
00:30and the appearance of disturbing microbes could soon follow.
00:34It is now imperative that the rest of the world is worried about it.
00:38The ice cap of Greenland, a real ice giant,
00:41covers about 80% of the island
00:44and houses nearly 8% of the world's freshwater reserves in the form of ice.
00:48For most of the year, it has been an immaculate vast area.
00:53However, at the arrival of summer, when temperatures rise,
00:57changes begin to appear.
00:59The melting of the ice reveals rocky outcrops on the coast,
01:03while as it progresses deeper into the interior of the land,
01:07the white ice, once uniform, becomes darker.
01:10This area, about 400 km long and 100 km wide at its widest point,
01:16presents this intriguing phenomenon for two main reasons.
01:19The first reason is related to black carbon.
01:22Like the dust that accumulates on your furniture,
01:25the ice cap of Greenland undergoes a similar process.
01:28The wind transports dust particles and sweat to these icy regions.
01:33But unlike your furniture,
01:35it is impossible to eliminate this accumulation with a simple blow of a rag.
01:38On Greenland's ice, this mixture of fine particles has been around for millennia.
01:43Thus, this dark area is covered by a thin layer of dust accumulated over time.
01:48In 2014, researchers studied this deposit
01:52and found that the darkest regions of the ice contained a high concentration of black carbon.
01:57This black carbon did not form by chance.
02:00In reality, it is mainly a result of the smoke
02:03generated by former forest fires in northern Canada and Alaska.
02:07As we can imagine, black carbon being dark in color,
02:11it causes a darkening of the surface of the ice.
02:15The second major cause of the summer transformation of the ice cap
02:19concerns the algae mentioned earlier.
02:21These are mainly two species,
02:23Ancylonema alaskana and Ancylonema nordenskjöldi.
02:28These algae are particularly fond of cold water environments.
02:32During the winter, they enter a state of dormancy
02:35and remain deeply buried in the ice,
02:37waiting for favorable conditions to reappear.
02:40When spring arrives,
02:42these algae begin to gradually rise to the surface.
02:45As summer approaches,
02:47they are ready to bloom
02:49and take advantage of almost 24 hours of sunlight every day
02:52to photosynthesize and grow.
02:55In normal times, these algae display a green tint.
02:58But once exposed to the sun,
03:00they turn brown,
03:02which is a natural protection against harmful ultraviolet rays.
03:06This change in color also contributes to the darkening of the ice of Greenland.
03:11Until now, this behavior was normal.
03:14What is really worrying
03:16is that the flow of algae increases in size every year.
03:20This phenomenon is explained by the fact that it prospers thanks to phosphorus,
03:24an abundant nutrient in this region,
03:27coming from a mineral called hydroxyapatite.
03:30The latter is found in a rock
03:32that decomposes into tiny particles of dust,
03:34transported by the wind through the ice.
03:37With global warming,
03:39the rocks become drier
03:41and stronger winds raise more dust.
03:44This increase leads to more phosphorus,
03:47thus favoring an increased growth of algae.
03:50Do you get it?
03:51It is a cycle that increases year after year.
03:54The study of this phenomenon is therefore essential
03:56to understand why the dark zone continues to expand.
03:59Between 2000 and 2012,
04:01its surface increased by 12%.
04:04You may be wondering about the gravity of this situation.
04:07After all, isn't it just the ice that becomes darker?
04:11Well, not quite.
04:13Think of your aversion to wearing black clothes
04:16on a hot and sunny day.
04:19They absorb heat and suffocate you.
04:22This is explained by the fact that dark surfaces
04:25capture more sunlight.
04:28The same goes for ice.
04:30Together, dust, black carbon and algae flora
04:34are responsible for about 70% of the variability of albedo
04:38on the ice cap of Greenland.
04:40Albedo is a technical term
04:42that refers to the ability of a surface to reflect light.
04:45If we compare two surfaces,
04:47one white and bright,
04:49the other dark and rough,
04:51the white surface will reflect a large amount of light and heat,
04:54which will give it a high albedo.
04:57Conversely, the dark surface will absorb more light and heat,
05:01resulting in a low albedo.
05:03During the summer, the ice cap of Greenland
05:06suffers a decrease in its albedo.
05:08This means that the ice captures more sunlight,
05:11and when it absorbs more,
05:13it melts faster than expected.
05:15This is why it is crucial to understand the dynamics
05:18within the dark zone.
05:20This allows us to predict the speed
05:22of the melting of the ice cap of Greenland
05:24and its repercussions on the rest of the world.
05:27The ice cap of Greenland
05:29is the second largest in the world,
05:31covering an area equivalent
05:33to that of all the American lands
05:35located east of the Mississippi River.
05:37This massive mass of ice
05:39has an average thickness of 2.3 km.
05:42But unfortunately,
05:44the rate at which this ice melts has exploded.
05:47In the 1990s,
05:49Greenland lost about 25 billion tons of ice per year.
05:53Today, this figure has risen to about 234 billion,
05:57which is nearly ten times more than the melted ice every year.
06:00According to NASA,
06:02if the entire ice cap of Greenland
06:04were to melt,
06:06it would lead to an elevation of the sea level
06:08of about 7.40 meters.
06:10This could have catastrophic consequences
06:12for countries and coastal cities
06:14around the world.
06:16The Netherlands could be completely submerged,
06:18the Bahamas could be almost completely destroyed,
06:21and many islands in the Philippines
06:23could disappear.
06:25All this may seem like a distant reality,
06:27and it is true that most scientists
06:29estimate that it would take several hundred,
06:32even thousands of years
06:34for the ice cap to melt completely.
06:37However, it is important to understand
06:39that Greenland has not always been covered
06:41by this thick layer of ice.
06:43Recently, researchers have carefully examined
06:45the sediments collected at the bottom
06:47of an ice core more than 3 km deep,
06:50extracted from the center of Greenland.
06:52They discovered that the soil contained
06:54traces of soil wood,
06:56parts of insects,
06:57mushrooms,
06:58and even poppy seeds.
07:00Thus, these fossils constitute
07:02our first direct evidence
07:04that the Greenland ice cap
07:06melted in a recent geological past,
07:08about 400,000 years ago.
07:10At that time, Greenland was covered
07:12by a greenish tundra landscape,
07:14populated by insects and plants.
07:16This discovery is both fascinating
07:18and disturbing,
07:20because it indicates that the ice cap
07:22has collapsed in the past
07:24and could be more fragile
07:26than what scientists initially thought.
07:28There is also another concern.
07:30A recent study has taken
07:32meltwater from different places
07:34in the Greenland ice cap
07:36and found that these samples
07:38contained hundreds of thousands of microbes.
07:40The concern lies in the fact
07:42that these microbes could be released
07:44into the ocean in the future.
07:46In addition, some studies already suggest
07:48that the areas close to the important
07:50flow of meltwater
07:52present an increased risk
07:54of transmission of viruses to new hosts,
07:56including animals to humans.
07:58Although experts estimate
08:00that the probability that a virus
08:02threatening humanity
08:04comes from glaciers is very low,
08:06it is not zero.
08:08In fact, we have little knowledge
08:10of the thousands of microbial species
08:12living on the surface of the ice.
08:14And there is simply not enough data
08:16to fully assess the dangers
08:18that these organisms could represent.
08:20All this may seem worrying,
08:22but there is no need to panic for the moment.
08:24There is still a lot to understand
08:26about the meltwater that darkens
08:28the Greenland ice cap.
08:30We need more precise measurements
08:32of the relative abundance of dust,
08:34algae and black carbon,
08:36as well as a better understanding
08:38of the potential impact
08:40of these microbes on our lives.
08:42The more we acquire knowledge,
08:44the better we will be able to anticipate
08:46the events to come
08:48and prepare ourselves accordingly.