ANTCI is a four year "collaborative
research" program
involving ten major institutions. This program includes two major
field studies (2003 and 2005) in Antarctica that will be conducted
during the Austral spring/summer months. The broad based goal of
this program
is to enhance our understanding of the processes that control tropospheric
levels of HOx, NOx, sulfur, and other trace species over the Antarctic
continent. The results will provide a far more comprehensive understanding
of Antarctic atmospheric chemistry as well as lead to further insights
about the atmospheric factors that influence the levels and distributions
of climate proxy species in Antarctic ice cores. Most important to
this study will be sulfur and nitrogen compounds and the atmospheric
oxidizing
agents that modulate their levels. Major science objectives include:
1) evaluating the detailed dynamical and chemical processes that control
spring/summertime levels of NOx/NOy and OH/HOx at South Pole; 2) assessing
the representativeness of South Pole and previous ground-based coastal
measurements to the larger polar and near shore Antarctica; and 3)
investigating the relative importance of the oxidative processes
involved in the coast-to-plateau
transport of reduced sulfur and determing the principal regions of
chemical transition. Of lower priority, are the following secondary
objectives:
1b) investigating snow/firn chemical species undergoing extensive exchange
with the atmosphere (e.g., NOx, HNO3, CH2O,
H2O2, and monocarboxylic
acids); and 2b) assessing the different chemical forms of the trace element
Hg and their relationships to the levels of O3,
OH and other oxidants.
Building on the results from several Antarctic field studies over the last
15 years, especially those from our recent projects SCATE (1994) and ISCAT
(1998, 2000), this new study, the Antarctic Tropospheric Chemistry Investigation
or ANTCI, entails experimental investigations at the South Pole and
extensive airborne sampling. Both the broader chemical scope of the proposed
science (HOx, NOx, sulfur, and other trace species) as well as the use
of extensive airborne sampling are reflections of the major new findings
from the NSF sponsored ISCAT project. More specifically, the finding that
very high and variable levels of NO are present in the atmospheric mixed
layer at South Pole has resulted in ANTCI focusing major attention on unraveling
OH/HOx and NOx/NOy chemistry. In addition, it is now evident from the ISCAT
results that insignificant amounts of reduced sulfur (e.g., marine released
dimethylsulfide, DMS) arrive at the South Pole during the Austral spring/summer
months. This was found to be true even though the transit time from coastal
sources in conjunction with model estimated oxidation rates would strongly
suggest otherwise. Collectively, these new findings have shown us an Antarctic
troposphere that appears to be very much different than that assumed for
planning either of the earlier NSF programs SCATE or ISCAT. Thus, even
though the oxidation chemistry of DMS continues to be of great interest
and will be pursued in ANTCI, the new findings have necessarily changed
the scope of the proposed project so as to address the most fundamental
issues in Antarctic tropospheric chemistry. As such several new measurements
have had to be added to the original ensemble defined in ISCAT. These include:
HO2, HNO3, HO2NO2,
PAN, HONO, NOy, CH2O, and H2O2.
Many of these measurements are being addressed by using innovative configurations
of the chemical
ionization mass spectrometry (CIMS) system (HO2,
HNO3, HO2O2)
or with state-of-the-science laser-induced fluorescence (LIF) technology
(CH2O, HONO), and still others
will be measured with established more conventional techniques. The wide
range of species to be measured will include not only those listed immediately
above but also NO, OH, SO2, DMS, DMSO, DMSO2,
MSA, H2SO4, CO, O3,
H2O,
NMHC's, organic acids, MS, nss-SO4-2,
Cl-, Na+, Hg, P, T, and UV irradiance.
With but two exceptions, the above list of species will be sampled simultaneously
at a resolution of 5 min or higher. When combined with the available meteorological
data, these observations should provide an extraordinarily rich database
for use as input to models. These will range from process oriented box
models to regionally focused GCTM's.
The ANTCI program, in addition to its major advancement of Antarctic atmospheric
chemistry, will provided an educational setting for the training of 5 to
7 new Ph.Ds. Through continuously updated websites, it will also bring
on-going research activity in Antarctica to other professionals, college
and high school students, as well as to the general public. Finally, the
data generated from these studies will be archived for all USA investigators
to use and will be exchanged with international Antarctic research groups
operating simultaneously at the coastal stations of Neumeyer and Halley
Bay.
