surface melt pulse is, arguably, best portrayed in the satellite
section of Western Greenland near the Jackobshavn Glacier
experiencing significant surface melt on July 20, 2016. Image
July 20th, this approximate 300 x 70 mile swath of Western Greenland
shows a number of distinct strong melt features. Near the interior
edge of the melt zone we notice the light blue coloration indicative
of widespread and general surface melt. From the satellite, this
bluing gives the impression of a thin layer of surface water covering
a widespread area of the ice sheet. But it is more likely that the
blue tint comes from a plethora of small melt ponds and rivers that
blend together in the lower resolution satellite shot to lend the
impression of ubiquitous water coverage.
Melt Ponds, Dark Snow Over Western Greenland
in, we notice the darker blue swatches that indicate large melt
ponds. Some of these ponds are quite extensive — measuring 1/4 to
up to 1 mile in length. Ponds of this size tend to put a lot of
pressure on the Greenland surface and can pretty quickly bore down
into the ice sheet’s depths and interior. The water then either
becomes locked in the ice — forming a kind ofsubglacial
or flows to base regions of the glacier where it can lubricate the
ice — causing it to speed up.
up satellite shot shows 1/4 to 1 mile long melt ponds, general melt
ponding and a darkened Greenland Ice Sheet. Image source: LANCE
closer to the ice edge we find greatly darkened patches of ice.
Darkening occurs when ice melt reveals and thickens past layers of
ice sheet dust and soot accumulation. Each year, winds carry dust
from land masses and soot from fires — which now, due to rapid
Earth warming, burn more frequently over the Arctic and near-Arctic —
to the ice sheet where it accumulates. This darker material is then
covered by the annual layers of snowfall. If enough snow and ice
melts, the yearly layers of dust and soot accumulation can
concentrate into a gray-black covering. Such a covering is clearly
visible in the July 20 satellite imagery above.
Northeastern Greenland Melt Also Visible
Isstrom Glacier in Northeastern Greenland shows significant melt in
July 20 satellite shot. Image source: LANCE
surface melt and darkening is quite extensive along the southwestern
flank of Greenland, toward the north and east, widespread surface
melt, ponding and ice darkening is also visible over sections of the
Zachariae Glacier. Here, in a far northern section of Greenland that
borders the Arctic Ocean, we find an approximate 100 x 20 mile region
of melting and darkening ice. Note the tell-tale bluing and dark gray
patches visible in the above image.
this region, ice has tended to experience more melt during recent
years as sea ice within the Fram Strait and Greenland Sea has
receded. This has revealed more darker ocean surfaces which, in turn,
has absorbed more incoming solar radiation resulting in increased
warming for this section of Greenland.
in Context — Human-Forced Warming Pushing Greenland to Melt Faster
Greenland melt is this year less extensive than the record 2012 melt
season. However, the current mid-to-late season pulse has forced a
big melt acceleration that may result in melt that exceeds 250
billion tons of ice loss for 2016 (or the average over recent years).
In the pretty near future, continued high global temperatures and
additional warming due to human fossil fuel emissions will almost
certainly push Greenland to melt at a faster pace.
this point, the
Earth has now warmed by more than 1 C above Preindustrial
And a range of 1-2 C warming from this baseline in past climate eras
such as the Eemian resulted in a 10-20 foot rise in world ocean
levels. We’re in this temperature range now. So that’s pretty bad
news for sea level rise — to which Greenland now contributes enough
melt to lift seas by about 0.75 mm every year. The only real
questions at this point are how fast will that already substantial
melt accelerate, and will we halt fossil fuel burning swiftly enough
to slow it down.