Friday, December 27, 2013

Science Links Arctic Melt to Our Climate Mayhem

Most of us had this figured out but a team of Chinese and American researchers has inked the link between Arctic snow and ice loss and the devastating heat waves, droughts and floods in the mid-latitudes.  You know -  Calgary and Toronto, the drought-stricken U.S. Midwest and  Southwest, flooding in Britain and central Europe, heat waves and crop failures in Russia, yada, yada, yada.

In other words, it's locked in

Good snow fall means lots of soil moisture in the summer months while dry ground tends to be warmer. So temperatures change, overall. Air currents flow because of pressure differences, which are linked to temperature. So winds would inevitably be affected.

But the researchers went beyond this loose generalisation, to match satellite observations of the snow cover and sea ice extent in the Arctic with atmospheric data, to explore the effects further south.
They found a distinct set of patterns of circulation associated with the loss of snow and ice.

The upper atmospheric winds in the north become weaker, and the jet stream shifts northwards, which means that weather systems become more stable. The longer a weather system stays in one location, the greater the probability that the conditions will become extreme.

In 2012, in the continental United States, it was the hottest summer ever recorded and the second worst for floods, hurricanes and droughts. In September 2012, the Arctic sea ice fell to its lowest level ever. It could be just chance, it could be just two aspects of the same big picture, but Tang and colleagues think not.

They think the link is clear. They even see a closer link between the loss of sea ice and a change in circulation pattern, even though the area of sea ice lost is only half of the total area of snow lost in the months of May and June.

That could be because much of the northern hemisphere snow cover is over land which is forested anyway – that is, partly dark – whereas the Arctic sea can only be white or dark.

The link is not certain – they are putting the idea out there for others to challenge or confirm, which is the way science advances – but the three authors argue that their research builds on studies by others which spell out the same conclusion.

As greenhouse gases continue to accumulate in the atmosphere and all forms of Arctic ice continue to disappear, we expect to see further increases in summer heat extremes in the major population centres across much of North America and Eurasia where billions of people will be affected”, they conclude.

Meanwhile California, North America's major market garden, remains in the grip of severe drought.  This could be the driest year ever.

The city of Los Angeles has received only 3.6 inches of rain this year — far below its average of 14.91 inches, USA Today reported. And San Francisco is experiencing its driest year since recordkeeping began in 1849. As of November, the city had only received 3.95 inches of rain since the year began.

The state is enduring its driest year on record and while a drought emergency has not yet been officially declared, the U.S. National Drought Monitor shows that as of December 24, nearly the entire state is gripped by severe to extreme drought conditions.

The portion of the state currently hit hardest by drought includes the Central Valley, a prime agricultural area, and “a lack of rain and snow this winter could bring catastrophic losses to California agriculture, as water allotments are slashed by state agencies,” USA Today reported.


Anonymous said...

When a large chunk of ice in a closed system begins to degrade you have to conclude that i) something is causing the degradation and ii) there will be changes to the closed system as a result of the degradation.

The average 10-year-old could figure that out.

The Mound of Sound said...

Yes I expect there are 10-year olds who could figure it out.