Permafrost ice a Quaternary climate archive?
Permafrost regions are known to be susceptible to recent climate warming particularly with regard to positive feedback mechanisms (e.g. by the potential release of stored carbon) from permafrost. However, little is known about the potential of permafrost ice so called ground ice to store climate and...
| Main Authors: | , , , , , |
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| Format: | Conference Object |
| Language: | unknown |
| Published: |
2009
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| Subjects: | |
| Online Access: | https://epic.awi.de/id/eprint/21057/ https://hdl.handle.net/10013/epic.33352 |
| Summary: | Permafrost regions are known to be susceptible to recent climate warming particularly with regard to positive feedback mechanisms (e.g. by the potential release of stored carbon) from permafrost. However, little is known about the potential of permafrost ice so called ground ice to store climate and environmental changes. Stable water isotope methods can under certain circumstances reveal climate information from permafrost ice and trace the changes through time. Stable water isotopes (δD, δ18O) are well established as mostly relative paleotemperature proxies for climate studies related to ice caps and glaciers in Greenland, Antarctica and other parts of the world. For permafrost research, the water isotopes have yet been underutilized.Ground ice is defined as all types of ice contained in frozen or freezing ground, including pore ice, segregated ice, as well as ice wedge ice. Ice wedges are most promising as paleoclimate archives. They are distinctive due to their vertically-oriented foliations and air bubbles. Ice wedges form as winter thermal contraction cracks are periodically filled by surface water (mainly from snow melt), which quickly (re)freezes at negative ground temperatures. The seasonality of thermal contraction cracking and of the infill of frost cracks are generally related to winter and spring, respectively. Ice wedges are, thus, assumed to be indicative of winter climate conditions. The processes involved are most likely free of any fractionation during freezing. Segregated ice forms by the process of ice segregation (motion of ground water in the sediment column towards a freezing front). Segregated ice is rather a mixture of winter and summer precipitation, which additionally has undergone fractionation during freezing. One must bear in mind that ground water in permafrost regions is mostly related to the active layer (a sub meter to meter thick layer, which melts in summer and freezes in winter). A third type of ground ice, so called pore ice also known as ice cement, is also intrasedimental ... |
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