Sahara desert sand is finding a newer, quicker route to the Arctic, sparks global warming fears
Millions of tonnes of Sahara desert dust being blown to the Arctic at rapid rates could speed up global warming, Abu Dhabi researchers revealed days after a UN report said the world has just 12 years to tackle climate change.
Huge plumes of dust being transported from North Africa to the Arctic on a new, shorter route could have stark consequences for climate change, new research from New York University Abu Dhabi (NYUAD) has found.
The revelation came through a study of a 2011 cyclone over Morocco that carried 38 million tonnes of dust, depositing 1.3 million tonnes of it in the Arctic.
Dust can travel 4,000km over three or four days on the newly-discovered route, halving the distance and time it usually takes for dust to reach the Arctic.
“Before, many studies pointed out pathways through Europe or through the Atlantic around the Bermuda High, very long pathways where most of dust settles in the ocean or over Europe on its way to the Arctic,” said Dr Diana Francis, an atmosphere research scientist at NYUAD who led the study.
“But this pathway is very short and reaches the Arctic in a few days, which means most of the dust is directly injected in the Arctic.”
The Arctic is highly susceptible to climate change, and its average temperatures have increased by 1°C in the last century, almost double the global average. Perennial sea ice lost half its cover between 1979 and 2012 and is declining at a rate of 11 per cent a decade.
This week, the UN issued a landmark report warning governments there are just 12 years left to respond to climate change.
The Earth is on track for an unliveable 3°C or 4°C rise, the report said.
The Earth's surface has warmed 1°C - enough to lift oceans and unleash a crescendo of deadly storms, floods and droughts - and is on track toward an unliveable 3°C or 4°C rise, the report stated.
Findings from the NYUAD study can be applied in models predicting global temperature changes and sea level rise that inform government climate change policy and response.
To understand the processes that cause glaciers to retreat and sea levels to rise, scientists like Dr Francis look at specs of dust thousands of kilometres away in the deserts of Africa and Central Asia.
Nearly two thirds of arctic dust comes from the Sahara and a quarter of the spring dust emissions in North Africa are caused by cyclones, which can produce two to eight teragrams of dust a day.
Yet little attention has been given on the effect of Saharan cyclones on the Arctic.
Once dust reaches the Arctic, it has a profound impact.
When dust and black carbon are absorbed into ice or snowpacks, they absorb more sunlight and accelerate ice melt. Additionally, nutrient-rich dust promotes the growth of bacteria and algae, which darkens the land and increases the number of holes in the ice, furthering increasing ice melt.
Even before the dust touches the land, it changes the skies. Coarse airborne particles scatter, absorb and emit longwave radiation, which changes the air circulation, affecting cloud formation and precipitation.
The dust from the 2011 cyclone was accompanied by warm and moist air masses that caused temperatures in southeast Greenland to increase by 10 degrees for more than three consecutive days in mid-April.
The research examines why dust from the cyclone travelled north instead of east, as would be expected.
“People talk about carbon dioxide in the atmosphere but we know that water vapour is four times more effective in warming than carbon dioxide,” said Dr Francis.
“There has been a lot of moisture transported to the Arctic in the last few decades and many studies think the melt and the changes in the ice coverage in Greenland are due to this transport of moisture.”
Dr Francis studied satellite imagery and numerical modelling of airborne particles at 72 different heights from 10m to 28km above the ground.
The new route is caused by changes in the polar jet stream, an air current that has slowed and deviated south from its usual location due to rising Arctic temperatures.
This meandering polar air current created the 2011 cyclone and transported the dust quickly north.
As polar jet streams become more frequent, more dust will be transported north and this will trigger a feedback loop. Further research could predict the frequency of such future events.
The findings provides new incentives for the study of air particles and light reflection at northern latitudes, said Dr Earle Williams, a research scientist at Massachusetts Institute of Technology.
“This interesting new study shows evidence from both observation and model that African continental cyclones in springtime can churn up dust and send it northward by 3,000 to 4,000 kilometres in latitude and as far as Greenland,” said Dr Williams, who specialises in physical meteorology and global dust transport.
The research was conducted over the past year and published this month in the Journal of Geophysical Research of the American Geoscience Union.
It makes a valued contribution to understanding climate systems, said researchers.
“This work is unique as it is the first time that anyone has shown how dust from the tropics can contribute to warming and melt on the ice sheet,” said Thomas Mote, an expert in Greenland ice melt and atmospheric circulation, and associate dean of the Franklin College of Arts and Sciences at the University of Georgia.
“It's an impressive illustration of important connections in the climate system from the tropics to the high Arctic.”
To understand our changing climate, sometimes the answer is blown in the wind.