TY  - THES
A1  - Macdonald, Elena
T1  - Stable isotopes in precipitation: Modelling intra-event variations using meteorological parameters
T1  - Stabile Isotope im Niederschlag: Modellierung von Ereignis-internen Variationen mit meteorologischen Parametern
N2  - Die kurzfristige Variabilität der Isotopenzusammensetzung von Niederschlägen in Golm, Deutschland wurde untersucht und modelliert. Dafür wurden Isotopendaten (D/H und 18O/16O) mit einer hohen zeitlichen Auflösung sowie meteorologische Daten von einer Wetterstation und einem Mikroregenradar genutzt. Nach der Datenaufbereitung und dem Zusammenführen aller drei Datensätze wurde eine multivariate lineare Regressionsanalyse durchgeführt. Dies geschah für vier verschiedene, auf den Isotopendaten beruhende Response-Variablen und für den gesamten Datensatz sowie für die zwei Teildatensätze Sommer und Winter. Die verwendeten Response-Variablen sind die Differenzen der δ18O-Werte zu den ereignisbasierten Mittel- und Medianwerten und die Differenzen der Deuterium-Exzess-Werte zu den ereignisbasierten Mittel- und Medianwerten. Für die erhaltenen Modelle wurden die modellierten Werte mit den gemessenen Werten verglichen, wobei sich herausstellte, dass die Messwerte nicht zufriedenstellend wiedergegeben werden konnten. Daher werden am Ende mehrere Vorschläge gemacht, wie das Vorgehen und damit auch das Ergebnis der Modellierung möglicherweise verbessert werden kann.
N2  - The short-term variability of the isotopic composition of precipitation in Golm, Germany was assessed and modelled. Isotopic data (D/H and 18O/16O) on intra-event timescales as well as meteorological data from a weather station and a micro rain radar was used. After data preparation and the combination of all three data sets, a multivariate linear regression analysis was conducted. This was done for four different isotopic response variables and for the entire data set as well as for the two subsets Summer and Winter. The used response variables are the δ18O values as the difference to the corresponding event-based mean and as the difference to the median, and the deuterium excess values as the difference to both the mean and the median. The models were evaluated by comparing the modelled values with the observed ones. This showed that the observations could not be reproduced in a satisfactory way. Therefore, several suggestions on how to possibly improve the methods and thus the modelling results are given in the end.
KW  - stable isotopes
KW  - isotopic composition
KW  - micro rain radar
KW  - multivariate linear regression model
KW  - stabile Isotope
KW  - Isotopenzusammensetzung
KW  - Mikroregenradar
KW  - multivariates lineares Regressionsmodell
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-506612
ER  - 
TY  - GEN
A1  - Münch, Thomas
A1  - Kipfstuhl, Sepp
A1  - Freitag, Johannes
A1  - Meyer, Hanno
A1  - Laepple, Thomas
T1  - Constraints on post-depositional isotope modifications in East Antarctic firn from analysing temporal changes of isotope profiles
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The isotopic composition of water in ice sheets is extensively used to infer past climate changes. In low-accumulation regions their interpretation is, however, challenged by poorly constrained effects that may influence the initial isotope signal during and after deposition of the snow. This is reflected in snow-pit isotope data from Kohnen Station, Antarctica, which exhibit a seasonal cycle but also strong interannual variations that contradict local temperature observations. These inconsistencies persist even after averaging many profiles and are thus not explained by local stratigraphic noise. Previous studies have suggested that post-depositional processes may significantly influence the isotopic composition of East Antarctic firn. Here, we investigate the importance of post-depositional processes within the open-porous firn (greater than or similar to 10 cm depth) at Kohnen Station by separating spatial from temporal variability. To this end, we analyse 22 isotope profiles obtained from two snow trenches and examine the temporal isotope modifications by comparing the new data with published trench data extracted 2 years earlier. The initial isotope profiles undergo changes over time due to downward advection, firn diffusion and densification in magnitudes consistent with independent estimates. Beyond that, we find further modifications of the original isotope record to be unlikely or small in magnitude (<< 1 parts per thousand RMSD). These results show that the discrepancy between local temperatures and isotopes most likely originates from spatially coherent processes prior to or during deposition, such as precipitation intermittency or systematic isotope modifications acting on drifting or loose surface snow.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 662 
KW  - Dronning Maud Land
KW  - near-surface snow
KW  - Ice core records
KW  - Kohnen Station
KW  - stable isotopes
KW  - water isotopes
KW  - polar firn
KW  - climate
KW  - diffusion
KW  - precipitation
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-418763
SN  - 1866-8372
IS  - 662
ER  -