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Global Change Master Directory (GCMD)
Firn Air Study in the Megadunes Near Vostok, Antarctica
Entry ID: severinghaus_nsf0230452


Summary
Abstract: This award supports a study of the chemical composition of air in the snow
layer (firn) in a region of "megadunes" near Vostok station, Antarctica. It
will test the hypothesis that a deep "convective zone" of vigorous wind-driven
mixing can prevent gas fractionation in the upper one-third of the polar firn
layer. In the megadunes, ultralow snow accumulation rates lead to structural
changes (large grains, pipes, and cracks) that make the permeability of firn to
air movement orders of magnitude higher than normal. The unknown thickness of
the convective zone has hampered the interpretation of ice core 15N/14N and
40Ar/36Ar ratios as indicators of past firn thickness, which is a key
constraint on the climatically important variables of temperature, accumulation
rate, and gas age-ice age difference. Studying this "extreme end-member"
example will better define the role of the convective zone in gas
reconstructions.

This study will pump air from a profile of ~20 depths in the firn, to
definitively test for the presence of a convective zone based on the fit of
observed 15 N/14N and 40Ar/36Ar to a molecular- and eddy-diffusion model.
Permeability measurements on the core and 2-D air flow modeling (in
collaboration with M. Albert) will permit a more physically realistic
interpretation of the isotope data and will relate mixing vigor to air
velocities. A new proxy indicator of convective zone thickness will be tested
on firn and ice core bubble air, based on the principle that isotopes of
slow-diffusing heavy noble gases (Kr, Xe) should be more affected by convection
than isotopes of fast-diffusing N2 . These tools will be applied to a test of
the hypothesis that the megadunes and a deep convective zone existed at the
Vostok site during glacial periods, which would explain the anomalously low
15N/14N and 40Ar/36Ar in the Vostok ice core glacial periods.

The broader impacts of this work include 1) clarification of phase
relationships of greenhouse gases and temperature in ice core records, with
implications for understanding of past and future climates, 2) education of one
graduate student, and 3) building of collaborative relationships with five
investigators.


The data sets will be:

1) firn air d15N, d40Ar, d86Kr, d136Xe, dHe/N2, dNe/N2, dAr/N2, dKr/N2, dXe/N2,
dO2/N2
2) firn air CO2 and methane
3) firn air halocarbons (CFC-12, CFC-11, HCFC-134a, CH3Br, and many more)
4) firn core and ice core density measured in the field
5) firn air carbon-14 of methane from the deepest sample
6) ice core d15N, dNe/Ar, dKr/Ar, d86Kr
7) ice core and firn core d18Oice, dDice, and deuterium excess
8) firn crack map at drill site
9) firn air model output including convective zone

Related URL
Link: View Related Information
Description: Abrupt climate change is the primary focus of research within the Severinghaus Laboratory.


Link: View Related Information
Description: Scientists from NSIDC have spent the last two Antarctic field seasons studying
one of the little-known megadunes areas of the continent. The NSIDC Research
Team, which included Ted Scambos, Rob Bauer, and Terry Haran, worked with a
team of other researchers and support staff in extreme weather conditions to
gather data in one of the most remote parts of the world. Unlike snow dunes
that are piles of drifted snow, Antarctic megadunes are long, undulating waves
in the surface of the ice sheet. The dunes are 2 to 4 meters (6.5 to 13 feet)
high and 2 to 5 kilometers (1 to 3 miles) apart.


Link: View Related Information
Description: The Antarctic Glaciological Data Center (AGDC) at the National Snow and Ice
Data Center (NSIDC) archives and distributes Antarctic glaciological and
cryospheric system data collected by the U.S. Antarctic Program.

Geographic Coverage
 N: -80.78 S: -80.78  E: 124.5  W: 124.5

 Min Altitude: 2896 M  Max Altitude: 2896 M

Data Set Citation
Version: Not provided


Temporal Coverage
Start Date: 1970-01-01


Location Keywords
CONTINENT > ANTARCTICA
GEOGRAPHIC REGION > POLAR


Science Keywords
ATMOSPHERE >ATMOSPHERIC CHEMISTRY    [Definition]
CRYOSPHERE >GLACIERS/ICE SHEETS >GLACIERS    [Definition]
CRYOSPHERE >GLACIERS/ICE SHEETS >ICE SHEETS    [Definition]
CRYOSPHERE >SNOW/ICE    [Definition]
PALEOCLIMATE >ICE CORE RECORDS >ISOTOPES    [Definition]
CRYOSPHERE >SNOW/ICE >SNOW/ICE CHEMISTRY    [Definition]
CRYOSPHERE >GLACIERS/ICE SHEETS    [Definition]
CRYOSPHERE >GLACIERS/ICE SHEETS >FIRN    [Definition]


Platform
FIELD SURVEYS    [Information]
GROUND-BASED OBSERVATIONS    [Information]
LABORATORY    [Information]
FIELD INVESTIGATION    [Information]


Instrument
CORING DEVICES    [Information]
FLASKS    [Information]


Project
NSF/PLR >Division of Polar Programs, National Science Foundation    [Information]


Keywords
megadunes
Antarctica
isotopes
ice cores
permeability
firn air
CO2
firn core
ice core density
deuterium excess
methane
carbon-14


Data Set Progress
ACTIVE


Data Center
National Snow and Ice Data Center    [Information]
Data Center URL: http://nsidc.org

Data Center Personnel
Name: NSIDC USER SERVICES
Phone: +1 (303) 492-6199
Fax: +1 (303) 492-2468
Email: nsidc at nsidc.org
Contact Address:
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
City: Boulder
Province or State: CO
Postal Code: 80309-0449
Country: USA

NSIDC Antarctic Glaciological Data Center    [Information]
Data Center URL: http://nsidc.org/agdc/

Data Center Personnel
Name: ROB BAUER
Phone: 303-492-2378
Fax: 303-492-2468
Email: bauer at nsidc.org
Contact Address:
University of Colorado
Cooperative Institute for Research in Environmental Sciences
CIRES 449 UCB
City: Boulder
Province or State: CO
Postal Code: 80309
Country: USA


Personnel
JEFFREY P SEVERINGHAUS
Role: INVESTIGATOR
Phone: 858-822-2483
Fax: 858-822-3310
Email: jseveringhaus at ucsd.edu
Contact Address:
Scripps Institution of Oceanography
9500 Gilman Dr.
City: La Jolla
Province or State: CA
Postal Code: 92093-0244
Country: USA


MARY R. ALBERT
Role: INVESTIGATOR
Phone: 603-646-0277
Email: mary.r.albert at dartmouth.edu
Contact Address:
Thayer School of Engineering at Dartmouth
14 Engineering Drive
City: Hanover
Province or State: NH
Postal Code: 03755
Country: USA


ROB BAUER
Role: METADATA AUTHOR
Phone: 303-492-2378
Fax: 303-492-2468
Email: bauer at nsidc.org
Contact Address:
University of Colorado
Cooperative Institute for Research in Environmental Sciences
CIRES 449 UCB
City: Boulder
Province or State: CO
Postal Code: 80309
Country: USA


Extended Metadata Properties
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Creation and Review Dates
DIF Creation Date: 2006-09-27
Last DIF Revision Date: 2018-10-01



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