Decadal to centennial variability of (sub-) Arctic sea ice distribution and its paleoenvironmental significance

• Main Author: Kolling, Henriette
• Format: Thesis
• Language: unknown
• Published: 2017
• Subjects: Arctic; Arctic Ocean; Baffin Bay; Baffin; Greenland; North Atlantic; Phytoplankton; Sea ice
• Online Access: https://epic.awi.de/id/eprint/52075/; https://hdl.handle.net/10013/epic.e50d3f38-b3cb-4b92-ad91-49c0bb886138

Arctic sea ice has major impact on the global climate as it affects the energy budget of the Earth and its export from the Arctic towards the North Atlantic has direct influence on the global ocean circulation. The observed modern sea ice loss, mainly associated with anthropogenic greenhouse gas emissions, has raised the concern about the role and natural variability of sea ice and its relation to short term changes in the climate system. The reconstruction of past sea ice changes based on sediment cores and analyses of specific proxies provides vital knowledge about the natural variability of sea ice in pre-industrial times. Moreover it helps to understand the present changes and may improve estimates for future changes and consequences. Particular important areas for sea ice reconstructions are the shelves around Greenland. They connect the Arctic Ocean to the North Atlantic and underlie the major outflow of freshwater and sea ice from the Central Arctic. In this context, a specific interval of interest for climate reconstructions is the late Holocene, as it exhibits modern boundary conditions, i.e., oceanography and geography, and encompasses several well-known short-term climate events, e.g., the Medieval Warm Period and Little Ice Age. For past sea ice conditions and open water phytoplankton production, the application of specific biomarkers, i.e., highly branched isopenoids (IP25, HBI III) and sterols (brassicasterol and dinosterol) have proven as useful and reliable proxies. However, their applicability, especially in regard to HBI III, is mostly confirmed on regional scales so far. The PIP25 index, the ratio of IP25 to an open water phytoplankton biomarker, is used for a more quantitative sea ice reconstructions. Aim of this study is to confirm the IP25/PIP25 approach in surface sediments on an over-regional scale and for specific regions, i.e., the Baffin Bay, by comparing them to satellite-derived modern sea ice concentrations. Further the PIP25 approach is compared to other common microfossil methods, ...