00:00These dark patches on Greenland's ice sheet aren't just any old stains.
00:06Every summer, the ice, which is usually bright white, turns murky gray in certain areas.
00:12This so-called dark zone was a huge mystery for a long time,
00:16until some studies discovered that this weird transformation was connected to the odd appearance
00:21of red, green, and brown-colored algae. The scariest part is that this algae bloom keeps
00:28growing. The dark zone is getting darker, and terrifying microbes might start appearing.
00:34Now, the rest of the world should be concerned.
00:37The Greenland ice sheet is like a massive ice blanket that covers around 80% of the island.
00:43It's so thick that it holds about 8% of the world's freshwater ice. For most of the year,
00:49the ice looks like a giant untouched white sheet stretching over the land.
00:53But when summer rolls around and temperatures start to rise, things begin to change.
00:58The ice melts, revealing rocky areas along the coast. And as you move further inland,
01:04that once smooth white ice becomes darker. This is the dark zone, and it covers an area
01:10of around 248 miles in length and 62 miles at its widest point. This weird phenomenon happens
01:18basically for two reasons. The first one is black carbon. Just like dust that builds up on your
01:24bookshelf, the ice in Greenland has the same issue. The wind carries a mix of dust and soot to this icy
01:31area. But unlike your bookshelf, you can't just wipe it off with a cloth. In Greenland's case,
01:37this dirty mix settles on the ice and sticks around for thousands of years.
01:41So, the dark zone is basically covered in a fine layer of dust that's built up over time. Back in
01:512014, researchers analyzed this dirty mix and found that the darker ice areas were filled with black
01:58carbon. This black carbon didn't just appear out of thin air. Well, actually, it sort of did.
02:04Scientists believe it mostly comes from smoke produced by wildfires in northern Canada and Alaska
02:10somewhere in the past. As you might guess, black carbon is black, which is why it makes the ice look
02:16darker. Now, the second big reason for the Greenland ice sheet's summer makeover has to do with those
02:25algae we mentioned earlier. We're mostly talking about two types of it. The Ancelonoma alaskana and the
02:32Ancelonoma norden scholdii. Both of them love cold water regions. During winter, they stay in a dormant
02:39state deep within the ice. But when spring comes, they start to slowly migrate to the surface.
02:46By the time summer hits, they're ready to bloom and soak up nearly 24 hours of sunlight each day for
02:52photosynthesis and growth. Normally, these algae are green. But when exposed to sunlight, they turn
02:59brown as a natural way to protect themselves from harmful ultraviolet rays. And this color change
03:05is also what makes the ice in Greenland look darker.
03:11So far, this has been normal behavior. What's really alarming is that these algae blooms are
03:16getting bigger and bigger every year. This happens because they thrive on phosphorus,
03:22a nutrient that's plentiful out there and comes from a mineral called hydroxyl lapatite.
03:27This mineral is found in a type of rock that breaks down into tiny dust particles, which are then blown
03:34across the ice by the wind. As the climate gets warmer, the rocks dry out more and stronger winds
03:40carry more dust. More dust means more phosphorus, leading to more algae growth. See? It is a cycle
03:48and it keeps getting worse every year. Studying this is crucial to understanding why the dark zone
03:55keeps getting bigger. From the year 2000 to 2012, its size increased by 12%.
04:02But you might be wondering, why should we care? After all, it's just ice getting darker, right?
04:10Well, not exactly. Think about how you can't stand wearing black clothes on a hot sunny day.
04:17They soak up the heat and make you feel even hotter. That's because darker surfaces absorb more sunlight.
04:22The same thing happens to ice. Together, dust, black carbon, and algae blooms are responsible for about
04:3070% of the variability in albedo on the Greenland ice sheet. Albedo is just a fancy word for how
04:37reflective a surface is. If you take two surfaces, one white and shiny and the other dark and rough,
04:44the white one will reflect a lot of light and heat, giving it a high albedo.
04:49The dark one, on the other hand, will absorb more light and heat, so it has a low albedo.
04:57During the summer, the Greenland ice sheet experiences a reduction in albedo.
05:03This means the ice absorbs more sunlight, and when ice absorbs more sunlight, it melts faster than it
05:08should. This is why understanding what's happening in the dark zone is so important. It helps predict how
05:15quickly the Greenland ice sheet is melting and how it can affect the rest of the world.
05:23Greenland's ice sheet is the second largest in the world, covering an area about the size of all the
05:29land in the United States east of the Mississippi River, and its huge mass of ice averages a thickness
05:35of 1.4 miles. Unfortunately, the ice loss has skyrocketed. Back in the 1990s, Greenland was losing
05:44about 25 billion tons of ice per year. Now, it's losing around 234 billion tons per year.
05:53That's nearly 10 times more ice melting away each year.
05:57According to NASA, if all of Greenland's ice sheet were to melt, it would increase global sea levels
06:05by about 24 feet. That could be catastrophic for coastal countries and cities around the world.
06:12The Netherlands could be submerged, the Bahamas could be almost completely wiped out,
06:17and many of the Philippines' islands would be at risk of disappearing.
06:21All of this may seem like a distant reality, and it is true that most scientists believe it would
06:28take several hundred or even thousands of years for the ice sheet to melt completely.
06:33But it is important to know that Greenland didn't always have this thick layer of ice.
06:39Very recently, researchers took a close look at some sediment from the bottom of a two-mile-deep
06:45ice core extracted from the center of Greenland. They found that the soil had traces of willow
06:51wood, insect parts, fungi, and even poppy seeds. So, these fossils are the first direct evidence
06:57that Greenland's ice sheet melted away in their recent geological past, around 400,000 years ago.
07:04At that time, Greenland was home to a green tundra landscape with insects and plants.
07:10This discovery is both fascinating and scary, because it shows that the ice sheet collapsed before
07:16and might be more fragile than scientists originally thought.
07:21There is another concern, too. A recent research collected meltwater from different spots on the
07:29Greenland ice sheet and found that the water samples were packed with hundreds and thousands
07:34of microbes. The concern is that they could be released into the ocean in the future.
07:39And some studies already suggest that areas near where a lot of glacial meltwater flows have a higher
07:45risk of viruses jumping to new hosts, like from animals to humans.
07:52Even though experts believe the chance of a doomsday virus coming from the glaciers is very small,
07:58it's still not zero. The truth is, we don't know much about the thousands of microbial species living on
08:05the surface of the ice, and there is simply not enough data to fully understand how dangerous these
08:11organisms might be. All of this might sound concerning, but we shouldn't panic just yet.
08:18There's still a lot we don't understand about what is darkening the Greenland ice sheet.
08:23We still need more detailed measurements of the relative abundance of dust, algae, and black carbon,
08:29as well as a better understanding of how these potentially dangerous microbes could affect our lives.
08:34The more we learn, the better we can predict what's going to happen and how we can prepare for it.
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