Last Glacial Maximum to Holocene Arctic sea-ice variability: Reconstruction from biomarkers
Arctic sea-ice extent has been declining rapidly throughout the past decades. To understand the past temporal and spatial sea-ice variability is of significant importance for predicting the future development. Within this thesis, the recently developed sea-ice proxy IP25, exclusively produced by dia...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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Universität Bremen
2014
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| Online Access: | https://media.suub.uni-bremen.de/handle/elib/689 https://nbn-resolving.org/urn:nbn:de:gbv:46-00103864-15 |
| Summary: | Arctic sea-ice extent has been declining rapidly throughout the past decades. To understand the past temporal and spatial sea-ice variability is of significant importance for predicting the future development. Within this thesis, the recently developed sea-ice proxy IP25, exclusively produced by diatoms in sea ice, has given a new insight into the reconstruction of sea ice across major parts of the Arctic Ocean during modern time and the Last Glacial Maximum (LGM). In the first study, determination of IP25, phytoplankton-derived biomarkers (brassicasterol and dinosterol) and terrigenous biomarkers (campesterol and ß-sitosterol) in surface sediments from the Kara and Laptev seas is used to estimate modern spatial (seasonal) sea-ice variability and organic-matter sources. C25-HBI diene and triene were determined as additional paleoenvironmental proxies in the study area. Furthermore, a combined phytoplankton-IP25 biomarker approach (PIP25 index) is used to reconstruct the modern sea-ice distribution more quantitatively. Neither IP25 nor PIP25, however, show a clear and good correlation with satellite sea-ice distribution due to the complex environmental conditions in our study area. Differences in the diene/IP25 and triene/IP25 ratios point to different sources of these HBIs and different environmental conditions. The diene/IP25 ratio correlates positively with sea-surface temperature, and thus might be used as a potential SST index. Further studies are, however, needed to validate this index. Furthermore, in the second study, a comprehensive data set of these biomarkers was produced using surface sediment samples from the Central Arctic Ocean proper (>80°N latitude) and the Chukchi Plateau/Basin. In addition, published data from other Arctic and sub-Arctic regions were added to the new data to generate an overview distribution map of IP25 across major parts of the Arctic Ocean. The phytoplankton biomarkers brassicasterol and dinosterol were also determined alongside IP25 to distinguish between two extreme ... |
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