45764
2016
2016
eng
1565
1581
17
12
article
Copernicus
Göttingen
1
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Regional climate signal vs. local noise: a two-dimensional view of water isotopes in Antarctic firn at Kohnen Station, Dronning Maud Land
In low-accumulation regions, the reliability of delta O-18-derived temperature signals from ice cores within the Holocene is unclear, primarily due to the small climate changes relative to the intrinsic noise of the isotopic signal. In order to learn about the representativity of single ice cores and to optimise future ice-core-based climate reconstructions, we studied the stable-water isotope composition of firn at Kohnen Station, Dronning Maud Land, Antarctica. Analysing delta O-18 in two 50m long snow trenches allowed us to create an unprecedented, two-dimensional image characterising the isotopic variations from the centimetre to the 100-metre scale. Our results show seasonal layering of the isotopic composition but also high horizontal isotopic variability caused by local stratigraphic noise. Based on the horizontal and vertical structure of the isotopic variations, we derive a statistical noise model which successfully explains the trench data. The model further allows one to determine an upper bound for the reliability of climate reconstructions conducted in our study region at seasonal to annual resolution, depending on the number and the spacing of the cores taken.
Climate of the past : an interactive open access journal of the European Geosciences Union
10.5194/cp-12-1565-2016
1814-9324
1814-9332
wos2016:2019
WOS:000381275100006
Munch, T (reprint author), Alfred Wegener Inst Helmholtz Ctr Polar & Marine, Telegrafenberg A43, D-14473 Potsdam, Germany.; Munch, T (reprint author), Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany., thomas.muench@awi.de
Initiative and Networking Fund of the Helmholtz Association [VG-NH900]
importub
2020-03-22T21:15:01+00:00
filename=package.tar
c908bdd3c6c6c9bedd8d32f4cb8d3906
Thomas Münch
Sepp Kipfstuhl
Johannes Freitag
Hanno Meyer
Thomas Laepple
Institut für Physik und Astronomie
Referiert
Import
44870
2016
2016
eng
1849
1860
12
121
article
American Geophysical Union
Washington
1
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Layering of surface snow and firn at Kohnen Station, Antarctica: Noise or seasonal signal?
The density of firn is an important property for monitoring and modeling the ice sheets as well as to model the pore close-off and thus to interpret ice core-based greenhouse gas records. One feature, which is still in debate, is the potential existence of an annual cycle of firn density in low-accumulation regions. Several studies describe or assume seasonally successive density layers, horizontally evenly distributed, as seen in radar data. On the other hand, high-resolution density measurements on firn cores in Antarctica and Greenland show no clear seasonal cycle in the top few meters. A major caveat of most existing snow-pit and firn-core-based studies is that they represent one vertical profile from a laterally heterogeneous density field. To overcome this, we created an extensive data set of horizontal and vertical density data at Kohnen Station, Dronning Maud Land, on the East Antarctic Plateau. We drilled and analyzed three 90m long firn cores as well as 143 one-meter-long vertical profiles from two elongated snow trenches to obtain a two-dimensional view of the density variations. The analysis of the 45m wide and 1m deep density fields reveals a seasonal cycle in density. However, the seasonality is overprinted by strong stratigraphic noise, making it invisible when analyzing single firn cores. Our density data set extends the view from the local ice core perspective to a hundred meter scale and thus supports linking spatially integrating methods such as radar and seismic studies to ice and firn cores.
Journal of geophysical research : Earth surface
10.1002/2016JF003919
2169-9003
2169-9011
wos2016:2019
WOS:000392830200013
Laepple, T (reprint author), Helmholtz Ctr Polar & Marine Res, Alfred Wegener Inst, Potsdam, Germany., tlaepple@awi.de
German Science Foundation [HO-5036/1-1]; Initiative and Networking Fund of the Helmholtz Association [VG-NH900]
importub
2020-03-22T13:47:01+00:00
filename=package.tar
bad69c395eaf2d59cacb2cf9a3029f55
Thomas Laepple
Maria Hörhold
Thomas Münch
Johannes Freitag
Anna Wegner
Sepp Kipfstuhl
Institut für Physik und Astronomie
Referiert
Import