Räumliche und zeitliche Variabilität von Wasserisotopen im polaren Niederschlag (Spatial and Temporal Variability of Water lsotopes in Polar Precipitation)

• Main Author: Werner, M.
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Hamburg 2000
• Subjects: Greenland; Antarc*; Antarctica
• Online Access: http://hdl.handle.net/21.11116/0000-0009-E332-E; http://hdl.handle.net/21.11116/0000-0009-E334-C

As with "normal" tHrtuo water molecules, the two stable water isotopes 'Hrt*O and tH2Ht6O 12H=D=Deuterium) are passed through every part of the water cycle in the atmosphere: water evaporates from ocean and land surfaces, is transported by atmospheric circulation, condenses in clouds and finally forms precipitation falling back to the earth's surface. But since HDO and Hr18O have a different vapour saturation pressure and molecular diffusivity than HrtuO, fractionation processes occur during every phase transition of any water sample. The heavier isotopes HrttO and HDO become enriched in the liquid or solid phase while the vapour phase becomes more depleted in them. The strength of the fractionation processes highly depends on particular physical parameters, such as temperature and humidity. Numerous geophysical studies have used this dependency to infer information about past climates from measure- ments of the isotopic composition of precipitation stored in paleowater archives, e.g. in ice cores. In the last several years, atmosphere general circulation models (AGCMs) have been used as a helpful tool for studying water isotopes. Incorporating both Hrtto and HDO explicitly into the water cycle of the AGCM enables analysing the relationship between the isotopic com- position of precipitation and climate variables, such as surface temperatures. Different boundary conditions can be prescribed for the model simulations to gain a better under- standing of isotope anomalies caused by different states of the climate. This thesis focuses on the variability of HrrsO and HDO in precipitation falling on Greenland and Antarctica. Over the last two decades, isotope measurements on several ice cores from both polar regions have revealed new insight in the alternating occuffence of stable climate periods, like the Holocene or the last glacial stage, and fast climatic transition phases between, such as the Younger Dryas. The Hamburg AGCM ECHAM-4 was used to investi- gate several topics related to these isotope records from ...