Mt Moulton Ancient Ice
 Antarctic
ice offers a unique repository of climate information to assess
the nature of climate change over the past half million years.
In the past, this record had been investigated largely through
analyses of deep ice cores. Detailed comparisons between other
global climate records and the Antarctic ice core records demonstrate
an amazing amount of shared variance on timescales ranging from
centuries to 100,000 years. However, all Antarctic ice cores that
contain ice older than 100 ka have been retrieved from East Antarctica.
At present we have no way of deducing how the West Antarctica
responded to the previous interglacial period (between 120 and
130 ka). A recent discovery suggests that a single paleotemperature
record from Antarctica may not, in fact, apply to the whole Antarctic
continent. Establishing how the West Antarctic ice sheet (WAIS)
responded to the previous interglacial period is important as
we need to assess the stability of WAIS to projected future climate
change in response to recent anthropogenic activities.
The summit of Mt. Moulton, in West Antarctica contains a 600-m
thick horizontally exposed section of ice with intercalated tephra
layers from nearby Mount Berlin. Dating of the tephra layers provides
an unprecedented chronology of climate change in WAIS between
14,500 and 492,000 years ago. Initial analyses suggest that the
Moulton site may offer an unparalleled repository of ancient West
Antarctic snow and trapped air that can be used to investigate
West Antarctic climate over as the last 500 years.
Todd Sowers
(Penn State University) and collaborative colleagues returned
to Mt. Moulton during the 2003-04 field season. Their purpose
was to:
- evaluate more thoroughly the integrity of the climatic record
through shallow drilling of the snow field upslope from the
blue ice region as well as into the blue ice itself.
- obtain baseline information about modern snowfall deposition,
mean annual temperature, and wind pumping around the summit
of Moulton.
- study how firn densification differs when surface accumulation
changes from net accumulation to net ablation.
In support off this project ICDS provided a 3" Eclipse drill,
which was operated by Sowers and his crew without ICDS drillers.
The following summary is from Sowers, dated 7/16/04.
Summary of Drilling at Mt. Moulton during the 03/04 Antarctic
field season
Our five member
group represented three separate institutions:
- Todd Sowers (PI) and Pratigya Pollissar from Penn State University
- Nelia Dunbar and Bill McIntosh from New Mexico Tech
- Trevor Popp from Univ. of Colorado (INSTAAR)
Trevor Popp and Bill McIntosh were primarily responsible for
the great success we had at Moulton. During our 3.5 week stay
at the summit, we set up the Eclipse drill in five separate locations.
We drilled over 203m of firn and 73m of Blue ice. The Blue ice
holes were especially interesting as we had to drill directly
into solid ice at the surface. We drilled two separate blue ice
holes to ~35m. We could easily have drilled deeper but were limited
by the amount of ice we could retrograde.
Preliminary results suggest we have an intact record of the Eemian
period with good radiometric dates on the tephra layers. We hope
this will provide the best-dated climate records for this interval
anywhere on the surface of the Earth. Having good radiometric
dates will then allow us to assess the hypothesis of orbital insolation
driven climate change for the previous glacial/interglacial transition.
Future publications and progress on the Moulton site will be
posted to the following web site:
http://www.geosc.psu.edu/~sowers/index.html
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