Decipher the mystery of the expanding "dark zone" of ice in Greenland

Researchers have just announced that they have solved the mystery of a growing “dark zone” in the melting ice of Greenland. It is caused by algal blooms, caused by phosphorus dust blowing through the wind.

According to information from scientists, phosphorus-rich dust blowing through the ice may be the key to this strange phenomenon.

Greenland’s ice is the second largest in the world. It covers an area of about 1.71 million square kilometers, an area three times the size of Texas, USA. However, Greenland’s ice is currently in a state of permanent thaw and loses 500 billion tons of ice every year.

That’s why the mysterious dark area is so disturbing. During the summer months, the western part of the ice sheet turns from brilliant white to dark gray as algae blooms on the surface. Since 2000, the algal blooms have grown larger and larger, causing the dark area to expand.

Decipher the mystery of the expanding "dark zone" of ice in Greenland
Algae blooms blacken the ice and increase thaw.

The darker color of the ice reduces the amount of sunlight it reflects back into space causing the ice sheet to absorb more heat.

“We see a lot of variation in the blooms that form on the surface of the iceberg,” said Jenine McCutcheon, a microbiologist at the University of Waterloo in Ontario and lead author of the new study. want to better understand what causes their development.”

During the sunless winter months of the Arctic, ice algae, mainly made up of Ancylonema nordenskioeldii and species in the genus Mesotaenium, remain dormant deep in the ice.

In the spring, when the ice melts, these algae slowly move to the surface. When they reach the surface, the Arctic summer provides 24 hours of sunlight for photosynthesis and growth. These algae are normally green in color, but when exposed to constant sunlight, they create a dark “sunscreen” to protect them from harmful ultraviolet rays. This is what makes the ice dark and ironically makes it absorb more sunlight.

But sunlight alone doesn’t seem to be enough to produce the large blooms the researchers are seeing.

After the researchers analyzed samples collected from the surface, it became clear that phosphorus was the most important nutrient for algae.

“We then discovered that it was locally sourced,” said study co-author Jim McQuaid, a climate scientist at the University of Leeds in the UK.

In Greenland, phosphorus comes from hydroxylapatite – a phosphate mineral that also contains calcium, oxygen and hydrogen – blown through the ice as dust from exposed rocky outcrops.

As the atmosphere warms due to climate change, the exposed rock layer becomes drier and winds stronger. This means more dust is transported through the ice.

Melting ice in the area also uncovers more hydroxylapatite-rich rocks, thereby increasing the amount of phosphorus available. So algal blooms are part of a positive feedback loop: Increased ice melt leads to higher phosphorus inputs, which promotes algae growth, which, in turn, further increases thaw.

When scientists fully understand the dark zone phenomenon, they can more accurately predict the rate at which ice melts in Greenland.

“If we could measure the amount of phosphorus in the environment, that could translate into an estimate of algae growth and allow us to better track the rate at which the ice melts,” McCutcheon said.