PERSONAL DE APOYO
DAPEÑA Cristina
congresos y reuniones científicas
Título:
Insights on the snow provenance of central western argentina using stable isotopes.
Autor/es:
MILANA, JUAN PABLO; DAPEÑA, CRISTINA
Lugar:
Bahia Blanca
Reunión:
Congreso; II Reunión Argentina de Geoquímica de la Superficie (II RAGSU).; 2012
Institución organizadora:
Instituto Argentino de Oceanografia (IADO, CONICET-UNS)
Resumen:
The South American Diagonal is a belt
over which the marginal effects of several climatic systems take place. In this
sense, we are interested in the interaction of the climate systems within this
arid region that are capable to produce snow storms, with the double objective
of finding an isotopic signature for each system, and if that exist, use it to
trace changes in the snow provision to local glaciers. It is well known that
while in Bolivia, glaciers are fed by heavy summer snow-storms coming from the
Amazon basin (the ?bolivian winter?), in subtropical latitudes of 32ºS,
glaciers are mainly fed by winter polar-front storms entering from the Pacific.
At the central Arid Andes of Argentina, the first system creates precipitation
out of a recycled amazonian-pampean water source (NE winds), while the second brings
water carried by polar fronts moving northeastward from the Southern Pacific
across the Andes (Zonda wind). A third snow supplying system is formed by the
south wind, which is a less intense and low altitude polar front that enters
from Patagonia and sometimes from the South Atlantic. All these three systems
create snow falls in the San Juan province.
Although the samples are not enough
to elaborate statistically correct assumptions, they illustrate about a
significant differentiation of the isotopic signature according to the sources
described above. The 2 samples from the first system showed d18O
values between -7.7 ? and -7.3 ? and d2H
between -34 ? and -33 ?, the three samples of the second system gave quite
different results, with d18O
between -10.5 ? and -9.8 ?and d2H
between -54 ? and -51 ?. The third system with 3 samples shows higher dispersal
with d18O
between -7.5 ? and -5.1 ? and d2H
between -39? and -21 ?. All samples have high deuterium excess (>25 ?). Although
these values are not common, similar values were previously reported in the
central dry Andes.
The preliminary hypothesis is that
samples seem to fall in two main families that differentiate sources: one with
more enriched values produced by recycled water from amazonian-pampean sinks
which produce summer snow storms and snow coming from weak winter fronts; and
the other snow produced out of pacific humidity groups quite different with depleted
compositions. These preliminary results suggests that it might be possible to
identify changes in snow supplied to subtropical glaciers, and therefore track
displacements of the ITCZ over longer periods of time and also the contribution
of the cold-warm ENSO and SPA anomalies. Additional information should be
obtained from glaciers fed today by these two dominant systems (pacific and
amazonian/pampean), in order to help identifying the related isotopic
signatures.