High resolution Palaeoclimatology of the Holocene Sub Polar North Atlantic

Type Thesis
Date 2009-08
Language English
Other localization https://ueaeprints.uea.ac.uk/10587/1/Thesis_miller_k_2009.pdf
Author(s) Miller Kathryn Rebecca1
University University of East Anglia
Discipline Environmental Sciences
Thesis supervisor Mark Chapman

A high resolution multiproxy investigation of two marine cores from the Gardar Drift in the Sub Polar North Atlantic, cores MD99-2251 and MD99-2252 has been undertaken to examine the extent of Holocene climate variability reflected by changes in diatom floral abundances and ice rafted debris flux. The results from this study provide both an overview of climate variability for the entire Holocene as recorded in the Sub Polar North Atlantic and a detailed high resolution study focussed around the 8.2kyr event. Sea surface temperature (SST) estimates are derived using a weighted average partial least squares (WAPLS) transfer function and a new regionally based diatom transfer function developed as part of this study. Principal component analysis and K-means cluster analysis were undertaken on core MD99-2251 to identify floral groupings within the diatom taxa. The changing composition of diatom assemblages and SST records indicate a highly unstable early Holocene from 11.5 to 9.5kyr with switches in the dominance of cool Sub Arctic floras and warmer North Atlantic floras. The presence of high productivity events in the diatom floras during this interval suggests that the core locations were, at times, in close proximity of the Sub Arctic Front. A broad SST cooling from 9.5 to 7kyr is identified followed by a pronounced warming for 7 to 5kyr and more stable but cooler temperatures during the Late Holocene. Changes in sea surface hydrography, especially the relative strength of the warm Irminger Current, is considered to have had the greatest influence on the composition of diatom floral assemblages. The 8.2kyr event is not recognised as a discrete climate perturbation in either the diatom assemblage data or the IRD record, but is contained within the broad cooling event from 9.5-7kyr. Analysis of sea-ice and cold water flora however does indicate some increase in these species for the interval 8.8 to 7.8kyr.

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