Global Change Abstracts The Swiss Contribution - SCNAT

126 Global Change Abstracts – The Swiss Contribution | Cryosphere | Oceans and Fresh Water
du Dome (4250 m) in 1994 and 2005, providing
clear evidence of atmospheric warming. The 1994
temperature profile was already far from steady
state conditions. Results from a heat transfer
model reveal that the englacial temperature increase
cannot be explained solely by atmospheric
temperature rise. The latent heat produced by the
refreezing of surface meltwater below the surface
also contributes to the englacial temperature increase.
Although surface melting is normally very
low at this altitude, this contribution became significant
after 1980 for temperatures at the top of
the borehole. Simulations for different climatic
scenarios show that glaciated areas located between
3500 and 4250 m could become temperate
in the future. This warming could have a major
impact on the stability of hanging glaciers frozen
to their beds if the melting point is reached.
Geophysical Research Letters, 2007, V34, N16,
AUG 18 ARTN: L16502.
08.1-235
Impact of monsoonal rains on spatial scaling
patterns in water chemistry of a semiarid river
network
Acuna V, Dahm C N
Switzerland, USA
Hydrology , Geochemistry & Geophysics
The chemical composition of surface waters of
nine streams with drainage sizes ranging from
44 to 8900 km(2) within a semiarid catchment
in the southwestern United States was examined
over the monsoonal season of 2006. Primary goals
were to determine the impact of monsoonal rains
on linkages between landscape cover features
and water chemistry in a semiarid river network
and to identify whether drainage size influences
the temporal variability in water chemistry of
streams. Landscape cover features (geology, soil,
and vegetation types) were quantified for the subcatchment
upstream of each study site and the
riparian ecotone. Processes of binary mixing, dilution,
and concentration were identified by end
member mixing analysis (EMMA). Results showed
that most chemical constituents corresponded
to geological features at the basin scale, but
other constituents (TSS and PO 4 3-) corresponded
more closely to riparian features. Importantly,
statistical relationships between land cover and
water chemistry differed between baseflow and
08.1-234
Introduction to special section: Permafrost and
seasonally frozen ground under a changing
climate
Zhang T, Nelson F E, Gruber S
USA, Switzerland
Cryology / Glaciology , Meteorology & Atmospheric
Sciences
Journal of Geophysical Research Earth Surface,
2007, V112, NF2, JUN 28 ARTN: F02S01.
1.5 Oceans and Fresh Water Systems
monsoonal conditions, suggesting that seasonal
changes in hydrologic routing and water sources
(e. g., overland flow versus groundwater sources)
have important consequences for stream chemistry.
In contrast with mesic drainages, temporal
variability in water chemistry increased with spatial
scale. The variety of contributing water sources
and the relative effect of dilution and concentration
in each spatial scale may be underlying
processes that explain differences across spatial
scales. Observed patterns in the Gila basin suggest
that climate variability interacts with hydrologic
routing to influence spatial patterns of stream water
chemistry in arid basins. Observations made
here may be similar to other systems with strongly
seasonal climate patterns, and the underlying
determinants of stream chemistry change with
drainage size.
Journal of Geophysical Research Biogeosciences,
2007, V112, NG4, DEC 1 ARTN: G04009.
08.1-236
The tracing of riverine U in Arctic seawater
with very precise U-234 /U-238 measurements
Andersen M B, Stirling C H, Porcelli D, Halliday A N,
Andersson P S, Baskaran M
England, Switzerland, New Zealand, USA
Geochemistry & Geophysics , Oceanography ,
Hydrology