International Polar Year 2007–2008 - WMO

The wealth of satellite data collected under
coordination of the IPY GIIPSY project is now enabling
new SAR image mosaics, interferometrically derived
ice sheet velocity fields at various frequencies, and
high-resolution SPOT Digital Elevation Models for
Greenland to be produced and distributed.
Arctic glaciers and ice caps
The Arctic glaciers and ice caps in most regions are
experiencing strong thinning at low elevations, while
the pattern at higher elevations varies from slight
thinning to slight thickening (Moholdt et al., 2010a,
b; Nuth et al., 2010). There are also examples of local
anomalous elevation changes due to unstable glacier
dynamics such as glacier surging (Sund et al., 2009).
For the Austfonna ice cap on Svalbard, the net
surface mass balance is slightly negative (-0.1 m water
eq. yr -1 ), but less negative than for the westerly ice
masses in Svalbard (Moholdt et al., 2010a). Iceberg
calving is important and contributes 30-40% of the
total mass loss, so the overall mass balance is a loss
of ~2 Gt yr -1 (Dowdeswell et al., 2008), however, the
elevation change measurements on Austfonna show
a thickening in the interior of ~ 0.5 m yr -1 , and an
increasing thinning closer to the coast of 1-2 m yr -1 ,
indicating a large dynamic instability (Dunse et al.,
2009; Moholdt et al., 2010a). This dynamic instability is
not seen on the Devon Ice cap.
Results from several IPY related research projects
have contributed significantly to characterizing
short- and long-term variations in the flow of several
major tidewater glaciers in the Canadian high Arctic.
RADARSAT-2 Fine and UltraFine beam mode data acquired
over the Devon Ice Cap since early 2009 reveal
sub-annual cycles of alternating accelerated/reduced
flow along the upper/lower reaches of Belcher Glacier.
Analysis of the LandSat image archive over major outlet
glaciers that drain the Devon Ice Cap and Manson
and Prince of Wales Ice Fields, indicates significant (up
to a factor of 4) inter-annual variability in tidewater
glacier velocities since 2000. Some, but not all, of this
is surge-related. Repeat mapping of glacier velocity
fields over the Devon Ice Cap from 1995 ERS 1/2 and
RADARSAT-1 data and 2009 RADARSAT-2 Fine beam
data indicates that (within limits of error) there has
been no net change in ice discharge from the ice cap as
a whole over this period of time. Finally, annual glacier
velocity measurements derived from RADARSAT-1 and
RADARSAT-2 Fine beam data indicate a net decrease in
the rate of flow of 11 target glaciers across the Queen
Elizabeth Islands between 2000 and 2010. This trend
was driven primarily by a few surge-type glaciers entering
the quiescent mode of glacier flow. Ongoing IPY
related glaciological research in Canada is focused on
understanding linkages between external climate forcing
and glacier dynamics and the impact of changing
glacier dynamics on the net mass balance and geometry
of ice caps in the Canadian Arctic.
Continuous GPS-receivers were used to monitor several
valley glaciers and outlet ice streams from the ice
caps, mainly in Svalbard and the Canadian Arctic. Clear
linkages between high melt events and increased flow
velocities can be seen at all (Ouden et al., 2010).
The recent increase in mass loss from the Canadian
ice caps is a result of strong summer warming, especially
since 2005, that is largely confined to the North
American side of the Arctic and also affects northern
and western Greenland. The IPY boreal summers 2007
and 2008 were two of the warmest five observed
since 1948. This warming seems to be attributable
to anomalously warm sea surface temperatures in
the NW Atlantic, and development of a high pressure
anomaly that extends from Iceland over the northern
2/3 of Greenland and the Canadian Arctic islands and
into the Canada Basin (sometimes reaching Northeast
Siberia). The circulation anomaly associated with this
latter feature favours atmospheric heat transport from
the northwest Atlantic up Baffin Bay into the areas
where strong warming in summer is detected.
An impact of this warming has been a major
change in the firnification regime of the Canadian ice
caps such that any semblance of a dry snow zone has
been eradicated and the upper limit of the wet snow
zone has risen substantially. Rates of firnification have
probably increased along with this.
On the basis of radio echo-sounding surveys of
glaciers on Franz Josef Land and Novaya Zemlya and
satellite altimetry data, characteristic heights and
thicknesses of glacier fronts producing icebergs have
been determined. This includes data for Glacier No. 1
and the Moscow Ice Cap on Hall Island, the northern
part of the glacier complex on George Land (Franz
Josef Land), and the glaciers in the Inostrantsev Bay
area, Novaya Zemlya. New criteria for the estimation
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