First posted at
robertscribler
What’s the difference between a majestic layer of white sea ice and an ominous dark blue open ocean?
For the Arctic, it means about a 30 to 50 per cent loss in reflectivity (or
albedo). And when seasonal sea-ice states are between 30 and 80 per cent
below 1979 measures (depending on the method used to gauge remaining sea
ice and relative time of year), that means very, very concerning
additional heating impacts to an already dangerous human-caused warming.
|
A dark and mostly ice-free Arctic Ocean beneath a
tempestuous swirl
of clouds on September 1, 2012,
a time when sea ice coverage had
declined to an
area roughly equal to the land mass of Greenland.
Image
source: Lance-Modis/NASA AQUA. |
How concerning, however, remained somewhat unclear until recently.
In the past, idealized climate simulations and physical model runs
had produced about a two per cent overall loss in Arctic albedo based on observed
sea ice losses. This decline, though minor sounding, was enough, on its
own, to add a little more than a 10 per cent amplifying feedback to the already
powerful human atmospheric carbon dioxide (CO
2) forcing during recent years. Such an
addition was already cause for serious concern and with sea ice totals
continuing to fall rapidly, speculation abounded that just this single
mechanism could severely tip the scales toward a more rapid warming.