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Passive
microwave satellite data are used to map snowmelt
extent and duration on the Greenland ice sheet. The total melt extent
of the ice
sheet, experiencing at least 1 melt day between April 1 - September 25
shows a
record extent in 2005
for the 27-year long time PM
data set. The 2005 melt extent exceeds the previous record of 2002. (Steffen et
al., 2004; Hanna et
al., 2005)
The
total melt area
for the same time
period in 2005 is slightly lower than 2002 (0.6%) and 1991
(1.1%) as of September 25th. However, we expect a record total
melt area for 2005 given the fact that the southern and western part of
Greenland are still melting in late September, whereas 2002 and 1991
experienced almost no melt in late September and during October. The
melt during October 2003 was 2.3 times that of 1991 and 4.3 times
that of 2002. We expect the melt of 2005 to be equal or even larger.
There
was extensive melt for 7 days during 2005 that covered ALL of southern Greenland including
South Dome at an elevation of 2900 m for 3 days. This event resulted in
the
largest melt area recorded on the ice sheet surpassing the previous
record in
2002. The 3-D view of
Greenland melt extent
shows the total melt area for 2005 and highlights the regions that
never melted
in the previous 26-year long PM record.
The melt extent for 1992 (minimum extent)
and for 2005
(maximum extent) are displayed in the same 3-D view of Greenland in
light red
(1992) and dark red (2005) color.
A record for total melt was observed for the north-west of the Greenland ice sheet in
the Thule region for
2005. There were
24 PM satellite pixels primarily in the higher
elevations in the northwest that melted in 2005 for the first time in
the
satellite record (27 years).
A summary of the melt extent and total melt for the entire Greenland ice Sheet and
for the north-western part (Thule) and the western part (Jakobshavn region)
is provided in the
following PDF file.
Detection of surface melt
at large spatial
scales is most effectively accomplished through the use of satellite
microwave
data, which has a clear melt signature that arises from the transition
from
volume- to surface-scattering during melt onset. As such, wet-snow
emission
approaches black body behavior, and this change in emission
characteristics is
detectable by most microwave sensors. These changes in emission
characteristics
have formed the basis of several passive-microwave-based melt
assessment
algorithms.
CIRES is a joint
institute of CU
[ About CU ]
and the National Oceanic and Atmospheric Administration
[ About NOAA ]
.
Steffen,
K., S.V. Nghiem, R. Huff, and G. Neumann, The melt
anomaly of 2002 on the Greenland Ice Sheet from active and passive
microwave
satellite observations, Geophys. Res. Lett., 31(20), L2040210.1029/2004GL020444, 2004.
Hanna,H., P.Huybrechts, I. Janssens,
J..Cappelen, K. Steffen, and A. Stephens, Runoff and
mass balance of the Greenland ice sheet:
1958–2003, J. Geophys. Res., 110,
D13108, doi:10.1029/2004JD005641, 2005.
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