Science Justification
The ice sheets of Antarctica and Greenland contain nearly
33 million cubic kilometers of ice. If all this ice were to melt, global sea level would rise by nearly
70m. On millenial time scales, the
West Antarctic Ice Sheet (WAIS) has the potential to raise sea level by
approximately 5m, with estimates of sea level rise rates of 1mm/year. However, the variability of West
Antarctic ice flow and Greenland ice flow on much shorter time scales is
well-documented (Zwally et
al., 2002)
The Intergovernmental Panel on Climate Change (IPCC)
predicts an approximately 1/2m rise of global average sea level by 2100 (IPCC,
2007) This assessment does not take into account recent
observations of rapid, non-steady variations in ice sheet flow speeds in
Greenland and Antarctica. The
Summary for Policymakers states that:
Models used to date do not include … the full
effects of changes in ice sheet flow, because a basis in published literature
is lacking.
They further warn that higher sea level could be possible
but that our ability to accurately predict ice sheet behavior is so poor that
they decline to even place an upper bound on their estimate. In addition to the flooding of coastal
regions and the consequent loss of property and life, the input of fresh, cold
meltwater could disrupt global ocean circulation patterns and lead to large,
abrupt, and unexpected climate change.
Technical Development:
The purpose of the GeoPebble is to replace the current
standard technique of multichannel seismic data acquisition. We currently use a Geode (from
Geometrics, Inc.,)
and a multi-conductor cable from the Geode to the geophones. The multi-conductor cable has takeouts
or pigtails at intervals along its length and each geophone plugs into the
takeout.
There are advantages and disadvantages to this setup. The primary advantage is that the power
system is centralized. The primary
disadvantage is that the cable is best suited for linear (2D) surveys. This shortcoming is important
enough to warrant development of a
replacement system that does away with the cable
We propose to develop a network of 150 GeoPebbles
that will perform digitizing close to the geophone and transmit the digital
data over a wireless link.
Each
GeoPebble will digitize all three components of the seismic wavefield and store
the data onboard for later processing.
The data will also be transmitted to a central site for “QC”
(in-the-field quality control).
Because there are no cables connecting the central site to the
geophones, the distribution of geophones can be determined by scientific
targets and needs rather than logistical concerns (as is now the case). The distributed nature of the network
and the local processing/digitizing capability will allow the GeoPebbles to
expand in future to include, e.g., meteorological instruments.
We emphasize that through CRESIS funding the design is
complete (working benchtop models are complete). CRESIS funding is being used to produce 6 fully functional
prototype units (anticipated completion in Spring 2008) that will form the basis
of the full GeoPebble network, for which we seek funding here.
Click on the slide to go to the presentation we made at the European Geophysical Union meeting in Vienna in April, 2008 (click on each slide to advance to the next one; use the back button on your browser to return here).
