Interpretation of temperature signals from ice cores

• Main Author: Münch, Thomas
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2018
• Subjects: ddc:530; Institut für Physik und Astronomie; Extern; Antarctic; Greenland; Kohnen; Kohnen Station; The Antarctic; Antarc*; Antarctica; ice core
• Online Access: https://publishup.uni-potsdam.de/frontdoor/index/index/docId/41496; https://nbn-resolving.org/urn:nbn:de:kobv:517-opus4-414963; https://publishup.uni-potsdam.de/files/41496/muench_diss.pdf

Earth's climate varies continuously across space and time, but humankind has witnessed only a small snapshot of its entire history, and instrumentally documented it for a mere 200 years. Our knowledge of past climate changes is therefore almost exclusively based on indirect proxy data, i.e. on indicators which are sensitive to changes in climatic variables and stored in environmental archives. Extracting the data from these archives allows retrieval of the information from earlier times. Obtaining accurate proxy information is a key means to test model predictions of the past climate, and only after such validation can the models be used to reliably forecast future changes in our warming world. The polar ice sheets of Greenland and Antarctica are one major climate archive, which record information about local air temperatures by means of the isotopic composition of the water molecules embedded in the ice. However, this temperature proxy is, as any indirect climate data, not a perfect recorder of past climatic variations. Apart from local air temperatures, a multitude of other processes affect the mean and variability of the isotopic data, which hinders their direct interpretation in terms of climate variations. This applies especially to regions with little annual accumulation of snow, such as the Antarctic Plateau. While these areas in principle allow for the extraction of isotope records reaching far back in time, a strong corruption of the temperature signal originally encoded in the isotopic data of the snow is expected. This dissertation uses observational isotope data from Antarctica, focussing especially on the East Antarctic low-accumulation area around the Kohnen Station ice-core drilling site, together with statistical and physical methods, to improve our understanding of the spatial and temporal isotope variability across different scales, and thus to enhance the applicability of the proxy for estimating past temperature variability. The presented results lead to a quantitative explanation of the ...