[ad_1]
The mystery of a growing “dark zone” on GreenlandThe melting of the ice cap has been resolved.
The researchers found that phosphorus– The rich dust blown on the ice may be the key to the phenomenon.
The Greenland ice cap is the second largest in the world. It covers approximately 656,000 square miles (1.71 million square kilometers), an area three times the size of Texas, according to the National Snow and Ice Data Center (NSIDC). However, the ice cap is now in a state of permanent retreat and is losing 500 gigatons (500 billion tonnes) of ice every year, Previously reported Live Science.
This is why the dark area is so disturbing. During the summer months, part of the western part of the ice cap turns from bright white to ink gray as algae blooms on the surface. Since 2000, these flowers have grown larger, causing the dark area to expand, according to a statement from the researchers.
The darker color of ice reduces its albedo – the amount of sunlight it reflects back into space – and causes the ice sheet to absorb more heat. However, until now, what triggers these algal blooms has remained a mystery.
Related: 10 signs the Earth’s climate is derailed
“We’re seeing a lot of variability in the blooms that form on the surface of the ice sheet,” said Jenine McCutcheon, a microbiologist at the University of Waterloo in Ont. And lead author of the new study outlining the findings. “We wanted to better understand what causes their growth,” she told Live Science.
Understanding algae blooms
During the sunless winter months of the Arctic, ice algae – mostly made up of Ancylonema nordenskioeldii and species in the Mesotaenium kind – stay in a state sleeping deep in ice. In the spring, as the ice melts, these algae slowly migrate to the surface. When they reach the surface, the arctic summer provides 24-hour sunlight for photosynthesis and growth. Algae are normally green, but when exposed to constant sunlight it creates dark colored sunscreens to protect against harmful ultraviolet rays. This is what darkens the ice and, ironically, causes it to absorb more sunlight.
But sunlight alone didn’t seem enough to cause the expansive blooms the researchers were seeing.
After the researchers analyzed the samples they collected from the surface, “it became clear that phosphorus was the most important nutrient for algae,” said study co-author Jim McQuaid, a climatologist at the University of Leeds in England. “We then found that it was sourced locally.”
In Greenland, phosphorus comes from hydroxylapatite – a phosphate mineral that also contains calcium, oxygen and hydrogen – which is blown onto the ice as dust from exposed rock outcrops.
“As the atmosphere warms due to climate change, the exposed rock becomes drier and the winds become stronger,” McQuaid said. “It means more dust is carried over the ice.”
Melting ice in the region also reveals more rocks rich in hydroxylapatite, thus increasing the available phosphorus. Algae blooms are therefore part of a positive feedback loop: increased ice melt results in higher phosphorus intake, which stimulates algae growth which in turn further increases seaweed melting. ice cream.
“This type of thing will continue to happen in the future; there is no doubt in my mind,” McQuaid said, referring to accelerated fusion.
However, now that scientists fully understand the Dark Zone phenomenon, they can more accurately predict how quickly the Greenland ice sheet will melt.
“If we can measure how much phosphorus is in the environment, maybe it will be possible to translate that into an estimate of algae growth and allow us to better track the rate of ice melt,” McCutcheon said. .
The study was published online January 25 in the journal Nature communications.
Originally posted on Live Science.
[ad_2]
Source link