International Polar Year 2007–2008 - WMO

series measurements ever made in these locations.
• Process studies were carried out at a number of
locations. In particular, the first direct measurements
of mixing in the deep Southern Ocean were made
during IPY as part of the Diapycnal and Isopycnal
Mixing Experiment in the Southern ocean (DIMES)
and Southern Ocean FINEstructure (SO-FINE)
projects.
• Measurements beneath the floating ice shelves and
glacier tongues that fringe much of Antarctica were
made at several locations. Observations within the
sub-ice shelf ocean cavities are very scarce, due
to the obvious difficulties of sampling the ocean
beneath hundreds of metres of ice. Nevertheless,
these measurements are needed to improve
understanding of how the interaction between the
ocean and the ice shelf can influence the dynamics
of the Antarctic ice sheet and how ice shelf melt/
freeze processes modify the ocean water. The AUV
Autosub3 made a number of long transits beneath
the Pine Island Glacier, where thinning, acceleration
and grounding line retreat have been observed
by satellites, measuring water properties and the
shape of the cavity (Jenkins et al., 2009). Access
to the ocean can also be gained by drilling holes
through the ice shelf and deploying oceanographic
instruments. IPY measurements were made
beneath the Amery Ice Shelf (70°E) and Fimbul Ice
Shelf (Greenwich Meridian; Lars Smedsrud, pers.
com.) as part of ongoing programs.
• Long-term sampling programs made a significant
contribution to IPY goals, including underway
measurements and remote sensing by satellites.
Model studies were carried out under the IPY
banner and contributed substantially to addressing
the scientific questions identified above.
Research highlights
The unprecedented spatial coverage of IPY observations
is providing new insights into the Southern
Ocean and its connection to the rest of the globe.
The deep hydrographic and tracer sections, Argo
floats and animal sensors have delivered a circumpolar
snapshot of the state of the Southern Ocean. The
IPY repeat hydrographic sections continue time-series
established in recent decades, allowing assessment of
changes in a variety of parameters throughout the full
depth of the Southern Ocean. Such studies have been
used to document the uptake of anthropogenic CO 2
by the ocean (e.g. Sabine et al., 2004), and the warming
(Johnson and Doney, 2006a,b; Johnson et al., 2007,
Fahrbach et al., 2010) and freshening (Aoki et al., 2005;
Rintoul, 2007) of Antarctic Bottom Water (AABW). For
example, Fig. 2.3-4 shows that freshening of the Adélie
Land and Ross Sea sources of AABW, observed in
those earlier studies, has continued through the IPY
Fig. 2.3-3.
Temperature at 200 m
depth, as measured
by traditional
oceanographic
platforms and
provided by the
Coriolis data centre
(ships and floats,
left) and by seals
equipped with
oceanographic
sensors (right). The
seals significantly
increase the number
of profiles obtained
in the sea ice zone in
winter (red).
(Images: Charassin et al., 2008)
s C I e n C e P r o g r a m 193