1. Introduction -- 2. Antarctic blue ice areas (BIAs) -- 2.1. Definition -- 2.2. Geographical distribution -- 2.3. Ice flow -- 2.4. Meteorology -- 2.5. Surface characteristics -- 2.6. Classification of blue ice areas -- 2.7. Dating -- 2.7.1. Meteorites -- 2.7.2. Radiodating -- 2.7.3. Isotopic dating -- 2.7.4. Dating of tephra layers -- 2.7.5. Geomorphology -- 2.7.6. Ice flow modelling -- 2.7.7. Combination of methods -- 2.8. Blue ice areas and climate -- 3. Methods -- 3.1. Precise GPS -- 3.2. Ground penetrating radar (GPR) -- 3.3. Mass balance studies -- 3.4. Dip angles of isochrones and surface age gradient in BIAs -- 3.5. Blue ice, firn, and snow samples -- 3.6. Isotopic analysis -- 4. Study area -- 5. Results and discussion -- 5.1. Mass balance and dynamics of the BIAs (papers I-IV) -- 5.2. Paleoclimate data (Paper IV) -- 5.3. Dating of surface blue ice (Paper III and IV) -- 5.4. On the age and stability of the BIAs (Paper IV) -- 3.5. Suggestions for future studies -- 6. References
Summary:
"Antarctic blue ice areas (BIAs) cover about 1 % of Antarctic surface area. The BIAs are known to have very old ice at the surface. This ice could be of great value for paleoclimatic purposes but the dating of the surface blue ice is demanding. Only few BIAs have been studied for paleoclimatic purposes although the temporal resolution in paleoclimatic data collected from the surface of a BIA can be higher than those of any of the vertical Antarctic ice cores. In this study, we focus on Scharffenbergbotnen, a blue ice area in Dronning Maud Land, Antarctica. Surface mass balance, ice flow velocities, and age gradient of the surface blue ice are determined by stake, ground penetrating radar, and differential GPS measurements. We estimate the surface age gradient and the age of our blue ice samples by adjusting a flowmodel to match with radiocarbon ages of the ice samples from the same area. The age gradients estimated by the flowmodel, by following isochrones with a ground penetrating radar, and by high resolution isotopic analysis are rather consistent. An isotopic analysis of a limited set of snow and blue ice samples can provide a fast and easy way to make a first estimation of the age of a BIA. A 101 m long continuous surface profile was also analysed for stable water isotopes from Scharffenbergbotnen BIA. According to the dating model the time period sampled is about a 500-year span of the mid-Holocene. The isotopic analysis imply that the mid-Holocene samples in Scharffenbergbotnen originate from a cooler climate period I than the present. Furthermore, comparison with 10500 year old ice shows that the modern climate is about 1.0±0.3°C warmer than the early Holocene climatic optimum in Scharffenbergbotnen. Many of the BIAs in mountainous areas of Dronning Maud Land are of Holocene origin. Changes in ice sheet thickness control the existence of the BIAs in the mountainous areas. Scharffenbergbotnen BIA was much smaller in the last glacial maximum than it is today. However, there are significant differences between the ice sheet elevation history in the mountainous areas of Dronning Maud Land and in central East Antarctica and Transantarctic mountains. This work emphasises that geophysical data must be combined with ice core analysis to get a reliable paleoclimate record. Although dating can be demanding, BIAs can provide high resolution paleoclimatic data that cannot be extracted from anywhere else"--P. [4].
