Last Glacial to Holocene variability in the sea ice distribution in Fram Strait/Arctic Gateway: A novel biomarker approach
The concern about the future development of Arctic sea ice also prompts a gaining interest in past variations of the ice extent in the Arctic Ocean. The important question as to whether the palaeo variability in sea ice coverage in this climate-sensitive area can be firstly identified, and secondly,...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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Universität Bremen
2011
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| Online Access: | https://media.suub.uni-bremen.de/handle/elib/221 https://nbn-resolving.org/urn:nbn:de:gbv:46-00102338-18 |
| Summary: | The concern about the future development of Arctic sea ice also prompts a gaining interest in past variations of the ice extent in the Arctic Ocean. The important question as to whether the palaeo variability in sea ice coverage in this climate-sensitive area can be firstly identified, and secondly, linked to climatic fluctuations thus motivates to look for tools that permit the reliable reconstruction of palaeo sea ice conditions. The recently established sea ice proxy IP25 is considered to be such a tool though a proper evaluation of the applicability of this biomarker hitherto has not been available. Within this thesis the occurrence of IP25 and its capability to display a previous sea ice coverage has been investigated by means of sediment cores from the Fram Strait - the only deep-water passage between the Arctic and Atlantic Ocean. Analyses of the biomarker composition of surface sediments revealed that the abundance of IP25 in these samples mirrors the recent, as derived from satellite and model data, sea ice distribution considerably well. It is found that the ice cover does not necessarily hamper but instead even may promote the phytoplankton productivity. This finding led to the establishment of a phytoplankton-IP25 (PIP25) index that facilitates the identification of different sea surface conditions (no ice, less/variable ice, marginal ice, perennial ice cover). Correlation analyses of these PIP25-based sea ice estimates with observed (and modelled) sea ice concentrations substantiate that this combinatory biomarker approach permits a more precise assessment of sea ice coverage than IP25 alone and could be used for quantitative (palaeo) sea ice reconstructions. Further, the Holocene variability in IP25 and phytoplankton biomarker contents of sediment cores from the continental margin of West Spitsbergen and East Greenland was studied. Throughout the Middle to Late Holocene, the sea ice cover increased in eastern Fram Strait, whilst the sea ice export along the East Greenland coast continued and ... |
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