ice researchers like to talk a lot about what they call ‘Century
Drops.’ Days when Arctic sea ice area or extent values fall more
than 100,000 square kilometers. In the past, daily Century Drops were
relatively rare — with steepest rates of loss occurring during late
June through early August and featuring, perhaps, a handful of days
in which 24 hour losses exceeded 100,000 square kilometers. But the
record melt years of 2007 and 2012 showed a proliferation of daily
drops that exceeded the 100,000 square kilometers daily threshold.
a couple of days ago a three Century Drop showed up in the Cyrosphere
Today measure. And it may just be something we’ve never seen
before. At the least, it’s an event that’s pretty amazingly rare
— or it should be, without the heat added to the Arctic by human
fossil fuel emissions.
Tuesday evening, the Cryosphere Today site showed Arctic sea ice at
about 8,966,000 square kilometers. The next day the measure stood at
about 8,646,000 square kilometers. That’s an extraordinary loss of
320,000 square kilometers in just one day.
Today sea ice graph shows that losses basically went vertical on
Tuesday, June 16. Image source: Cryosphere
square kilometers gone in a single 24 hour period. That’s an area
of sea ice the size of the state of New Mexico gone in a single day.
In the above graph, you can see the drop as the vertical turn in the
yellow line denoting 2015.
massive single day drop temporarily brought sea ice area in the
Cryosphere Today sea ice area chart into the range of second lowest
on record for the date. Area losses of around 70,000 square
kilometers for Wednesday resulted in a retreat to around 4th lowest
on record. But any period in which drops of this size become frequent
would easily transport the measure into new record low territory.
the tell-tale blue of melt ponds all over the Arctic Ocean and most
concentrated in edge zone regions. Proliferation of melt ponds during
early season, especially when combined with the impact of human
caused global warming, can increase risk for new record lows by end
cause of such a large single day drop is likely due to a combination
of factors. Lately, storms have been more prevalent in the Arctic
Ocean proper and such storms have a tendency to spread the ice out
more, opening gaps in the ice called polynyas which tends to push the
sea ice area measure lower. In addition, there is melt pressure now
in Baffin Bay, Hudson Bay, the Kara Sea, the Laptev Sea, the Beaufort
Sea, the Chukchi Sea, The East Siberian Sea, the Canadian Archipelago
waters, and in the Barents border region. This basically composes the
entire border zone of the Arctic sea ice.
the NASA MODIS satellite composite for recent days has shown a marked
shift toward a light blue coloration for the entire Arctic Ocean zone
and especially for the border zones. Such a shift is indicative of a
proliferation of melt ponds. Major snow cover losses over sea ice
during the past two weeks have removed insulation to the sea ice pack
and probably aided in the formation of these melt ponds. Melt ponds
are a strong indicator for sea ice health throughout the melt season
— so a proliferation of melt ponds at this time may be a sign of
sea ice melt vulnerability (see
more over at Neven’s Arctic Sea Ice blog where they do a bang-up
job tracking seasonal melt ponds and their potential impacts).
a three Century drop occurred, melt overall still has some catching
up to do to make 2012 levels. So though this massive daily drop
occurred, we are not yet in the red zone for sea ice area. Sea ice
extent measures, on the other hand, remain in the range of second to
third lowest on record and are still very close to all time record
low levels. So this particular melt season is certainly one to still