All data from the
Danish Meteorological
Institute (DMI)
in Copenhagen:
The end of August is the end
of the melt season for the
Greenland ice sheet.
The surface of the ice sheet
gained 169bn tonnes of ice
over 2018-19.
Using new satellite data,
the Greenland ice sheet
saw a net decline of
329bn tonnes of ice.
The beginning of September
is the start of a new annual
cycle for the Greenland
ice sheet.
The ice sheet largely gains snow
from September, accumulating
ice through autumn, winter
and into spring.
In late spring, the ice sheet
begins to lose more ice
through surface melt
than it gains from fresh
snowfall, through August.
The contrast between snow gains
and ice losses at the surface
over the whole year is known
as the “surface mass balance”
(SMB).
This year has
been consistently
drier than normal,
reflected in the
below-average
gains in snow
throughout
the year.
And the summer
had been warm,
with some periods
of very high melt.
The 2016-17 and
2017-18 seasons
had above-average
gains in ice
at the surface.
The SMB in 2018-19
ends as the
seventh lowest
on record.
SMB is always positive
at the end of the year –
more snow falls
on the ice sheet
than melts
at the surface.
But the ice sheet
also loses ice
by the breaking off,
or “calving”,
of icebergs
and from ocean
melting at its edge.
On average
between 1986 and 2018,
the ice sheet discharges
about 462bn tonnes
per year.
This year's satellite analysis
suggests Greenland discharged
around 498bn tonnes of ice.
For 2018-19,
DMI estimates
the ice sheet had
a total net ice loss
of around
329bn tonnes,
compared with
an average of
260bn tonnes
of ice per year
between
2002 and 2016,
with a peak
of 458bn in 2012.
Weather stations
in the Programme
for the Monitoring
of the Greenland
Ice sheet (PROMICE)
network recorded
ice loss rates
in excess of the
2008-18 average,
at every one of its
21 locations across
the ice sheet.
Weather stations
managed by the
Danish Meteorological
Institute (DMI),
located off
the ice sheet,
but with
longer records
– also showed
well above average
temperatures
at all locations
in June and July.
At the peak
of one heatwave,
the DMI model
calculated that the
Greenland ice sheet
lost 31bn tonnes of ice
– equivalent to about
+0.1mm of global
sea level rise –
in the three days
from July 31, 2019
to August 2, 2019.
An average melt
over those
three days
would be about
15 tonnes --
half as much.