Hey there Guys and Gals, I hope your well and lifes dealing you a decent hand. We're talking the Holocene, Climate Change and Peatlands, so kick back and enjoy the update.
The Holocene is a Geological period widely defined as the past 10,000 radiocarbon years BP (Roberts 1998). It encompasses the era of the current warm interglacial climate and has in the literature been previously described as a reasonably stable period of climate (O'brien et al. 1995). This assumption has however, been challenged in recent studies and this blog seeks to look at the role of Peatlands in this advancement of the study field.
The Holocene presents a particularly relevant period for study as it provides the most extensive and well preserved paleo-proxies of environment within the geological record which exist to the present, as well being subject to the same natural primary forcers of climate as present. These two factors provide a basis on which paleo-proxy data can be calibrated and form the basis for robust models of environmental change given certain forcing’s, such as anthropogenic climate change.
Peatlands constitute valuable geological records and are recognised as such within conservation scheme outlines for SAC sites under the European Commission’s Habitat Directive. Due to peats forming at a relatively slow rate and producing an anaerobic environment the stratigraphic structure provides, cores of peat which are dateable and contain well preserved organic substrate, pollen and potentially human artefacts.
Below are two videos that outline the underlying principles of Radiocarbon dating and Pollen analysis (Palynology), the first 3 minutes of both are all that’s really needed:
Video 1: The principles of RadioCarbon dating
Video 2: Palyonology, the basic concept. I'm afraid that the video libray on the topic was limited, but the example of application in honey used here is the method as for paleao pollen spore analysis.
A major development in the study of Holocene climate instability was that of ice rafting events occurring on a millennial time-scale within the North Atlantic. Climate was affected by cool, ice-bearing waters which were advected towards the latitude of Britain while at approximately the same time atmospheric circulation above Greenland changed dramatically (Bond et al. 1997). These events were identified by xenolyths of coarse sediment found within deep ocean cores transported to these low energy regions by icebergs.
Radiocarbon analysis of circumartic peat deposits has identified peatlands forming as early as 16,500 years BP while an explosion in their surface coverage occurred from 12-8000 years BP. This transpired in relation to a decrease in ice cover, high summer insolation and increased temperatures (Macdonald et al. 2006). Many Peatlands have subsequently undergone a transformation from Fen within the Early Holocene to Ombrotrophic bog communities in the late Holocene.
Walton Moss bog in Cumbria has followed this pathway. A highlighted shift from early Holocene fen and fen-carr communities to a deep mire water table and oligotrophic conditions is noted by Hughes et al. (2000). Sphagna species indicative of ombrotrophic conditions majorly increased from 7800cal. BP. and this corresponds to a “wet” shift in climate which is followed by 6 others. These all correspond to dated records in Bolten Fell Moss Bog located in Cumbria, but also blanket peat sites located in the Pennines, Scottish Borders and other European Mires. The wet shifts in Walton Moss found within the mid Holocene which can be more securely dated, when plotted in relation to the periodicity of ice rafting events described by Bond et al. (1997) bear a significant relation. Therefore Hughes et al (2000) suggest that potentially the regional climate and therefore development of Walton Moss Bog and others may have been driven by Ocean forcing.
Cheers
Matt
References:
Bond, G., Showers, W., Cheseby, M., Lotti, R., Almasi, P., deMenocal, P., Priore,P., Cullen, H., Hajdas, I. & Bonani, G. (1997) A pervasive millennial-scale cycle in North Atlantic Holocene and glacial climates. Science,
Hughes, P. D. M. D. Mauquoy, K. E. Barber and P. G. Langdon (2000) Mire-development pathways and palaeoclimatic records from a full Holocene peat archive at Walton Moss, Cumbria, England.The Holocene, 10, 465-479.
MacDonald, Glen. M., David, W. Beilman., Konstantine, V. Kremenetski., Yongwei, Sheng1., Laurence, C. Smith., Andrei, A. Velichko.(2006) Rapid Early Development of Circumarctic Peatlands and Atmospheric CH4 and CO2 Variations. Science, 314, 285-288
Great article Matt! Definitely should have given peatlands more mention when talking about Holocene climate proxies in my recent post...
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