Geoscience Reference
In-Depth Information
Keywords Paleoclimatology
Climate modeling
Solar variability
Westerly winds
1 Introduction
The westerlies are major zonal atmospheric circulation systems in both northern and
southern hemispheres. Particularly, the southern westerly wind belt (SWW) exerts a
strong control on global climate and oceanography. On a hemispheric scale, SWW
changes contribute substantially to the forcing of the deep and vigorous Antarctic
Circumpolar Current, while wind-induced upwelling in the Southern Ocean raises
large amounts of deep water to the surface affecting the global thermohaline cir-
culation and atmospheric CO 2 contents. Observational data suggest
southern margin of the SWW has intensi
ed over the past 40 years, a trend that is
expected to proceed over the next centuries. This may provide a positive feedback
on global warming through reducing the uptake of anthropogenic CO 2 or even
promoting outgassing of old naturally stored CO 2 through upwelling.
Southern South America is the only landmass intersecting both the present core
(southernmost Patagonia) and the northern margin (central Chile) of the wind-belt.
Since the SWW nearly entirely control precipitation on the western side of the
southern Andes, proxy records of past precipitation changes from this region are
ideal to reconstruct past variability of the SWW. Furthermore, the ocean margin,
lake, and fjord sediments provide high resolution paleoclimate archives along the
southern Chilean continental margin suitable to reconstruct precipitation changes
and related ocean variations during the Holocene (e.g., Kilian and Lamy 2012 ).
These sediment records combined with climate modeling can be used to place the
short instrumental data-sets into a longer-term perspective covering centennial-
millennial-scale SWW changes during the complete Holocene.
2 Materials and Methods
Our primary goal is to integrate southern Chilean lake, fjord, and ocean margin
proxy archives with climate modeling in order to reconstruct Holocene changes
in vegetation, rainfall, and lake/sea-surface temperatures and relate those to changes
in the strength and latitudinal position of the SWW. Therefore, we applied a number
of different methods including non-destructive core-logging methods to obtain
ultra-high-resolution records, sedimentological, and palynological approaches
(Lamy et al. 2010 ). Large efforts were devoted to generate detailed and reliable age
models by radiocarbon dating and tephrostratigraphy. Furthermore, we investigated
the regional calibration and applicability of novel organic biomarkers including
glyceryl dialkyl glycerol tetraether (GDGT)
based proxies (such as TEX86 to
Search WWH ::

Custom Search