Glacial dust blowing into the Gulf of Alaska. [GALLO/GETTY]

Most people are aware of dust in the atmosphere. It produces a whitish haze, reducing visibility at times. Deposits of dust occur when it rains and reddish dust from North Africa occasionally falls across France and the UK when the winds are from a southerly direction.

The dust is known to have an effect on weather systems. Huge amounts of dust blow from the Sahara desert across the Atlantic Ocean. Some 60 to 200 million tons travel across the Atlantic Ocean every year. It is known that that the dust has a negative impact on hurricane formation.

Another source of atmospheric dust is less well known . The NASA above shows glacial dust, known as flour, drifting southwestwards from the Copper River delta and extending more than 100km southwestwards into the Gulf of Alaska.

This dust, which results from the grinding action of glaciers on the underlying bedrock, adds to atmospheric pollution. Studies are taking place to examine the likely effect this dust will have on human health. It is thought that, as glacial retreat continues, the quantity of glacial flour in the atmosphere will increase significantly.