International Polar Year 2007–2008 - WMO

Fig. 2.3-12. Dead
krill on the beach at
King George Island
as a consequence
of increased fresh
water and sediment
discharge.
(Photo: Eva Philipp)
206
IPY 20 07–20 08
ellite (ICESat) was adjusted to ensure that the 33 day
L3I mission of the onboard laser altimeter coincided
with the two IPY field programs thus ensuring nearcoincident
field and satellite overpass data. The possibility
of collecting coincident data in the field was,
unfortunately, thwarted by bad weather, but regional
calibration and validation studies were possible.
Under-ice measurements were made using a ROV
during SIPEX to determine the abundance of algae
under the ice, along transects marked out from the
surface. Additionally, a Surface and Under-ice Trawl
(SUIT) system was specially made to trawl for krill
under ice floes adjacent to the ship’s track.
Process studies formed an integral part of both the
SIPEX and SIMBA programs, including the deployment
of two arrays of GPS-tracked drifting buoys to measure
ice drift and dynamics (SIPEX) and ice mass balance stations
to measure in situ changes in ice and snow thickness
over a 30 day period (SIMBA). Geophysical measurements
assessed the presence of flooded sea ice;
ice structure, including the presence of snow ice, was
determined from laboratory analysis of sea ice cores.
Biogeochemical analyses were conducted to measure,
among other things, the accumulation of iron in the
sea ice and the processes by which it is concentrated
from the water column during ice growth. The brine
channel structure of the ice and its importance for biological
and biogeochemical processes was also examined
using standard geophysical techniques.
Research highlights
The IPY programs afforded a rare opportunity to
conduct coincident field studies in the Antarctic pack
ice, on different sides of the continent. The results show
that the sea ice in east Antarctica was more dynamic,
swell affected and more heavily deformed in some
areas than in west Antarctica where more compact,
homogenous ice was encountered, particularly at the
southern-most end of the ship transect. The in situ
ice and snow thickness data show generally good
agreement with the satellite data, but provide new
insights into the buoyancy theory calculations used
to calculate sea ice thickness from satellite freeboard
measurements (Worby et al., in press; Xie et al., in
press). In particular, the relationship between ice and
snow thickness varies between the two study regions.
Negative ice freeboards were common in both east
and west Antarctica, as was the formation of flooded
layers and snow ice, however, an empirical relationship
equating mean freeboard to mean snow thickness