Identification of paleo Arctic winter sea ice limits and the marginal ice zone: Optimised biomarker-based reconstructions of late Quaternary Arctic sea ice
Analysis of >100 surface sediments from across the Barents Sea has shown that the relative abundances of the mono-unsaturated sea ice diatom-derived biomarker IP25 and a tri-unsaturated highly branched isoprenoid (HBI) lipid (HBI III) are characteristic of the overlying surface oceanographic cond...
| Published in: | Earth and Planetary Science Letters |
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| Main Authors: | , , , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Elsevier BV
2015
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| Subjects: | |
| Online Access: | http://hdl.handle.net/10026.1/4335 https://doi.org/10.1016/j.epsl.2015.09.020 |
| Summary: | Analysis of >100 surface sediments from across the Barents Sea has shown that the relative abundances of the mono-unsaturated sea ice diatom-derived biomarker IP25 and a tri-unsaturated highly branched isoprenoid (HBI) lipid (HBI III) are characteristic of the overlying surface oceanographic conditions, most notably, the location of the seasonal sea ice edge. Thus, while IP25 is generally limited to locations experiencing seasonal sea ice, with higher abundances found for locations with longer periods of ice cover, HBI III is found in sediments from all sampling locations, but is significantly enhanced in sediments within the vicinity of the retreating sea ice edge or marginal ice zone (MIZ). The response of HBI III to this well-defined sea ice scenario also appears to be more selective than that of the more generic phytoplankton biomarker, brassicasterol. The potential for the combined analysis of IP25 and HBI III to provide more detailed assessments of past sea ice conditions than IP25 alone has been investigated by quantifying both biomarkers in three marine downcore records from locations with contrasting modern sea ice settings. For sediment cores from the western Barents Sea (intermittent seasonal sea ice) and the northern Norwegian Sea (ice-free), high IP25 and low HBI III during the Younger Dryas (ca. 12.9-11.9 cal.kyr BP) is consistent with extensive sea cover, with relatively short periods of ice-free conditions resulting from late summer retreat. Towards the end of the YD (ca. 11.9-11.5 cal.kyr BP), a general amelioration of conditions resulted in a near winter maximum ice edge scenario for both locations, although this was somewhat variable, and the eventual transition to predominantly ice-free conditions was later for the western Barents Sea site (ca. 9.9 cal.kyr BP) compared to NW Norway (ca. 11.5 cal.kyr BP). For both locations, coeval elevated HBI III (but absent IP25) potentially provides further evidence for increased Atlantic Water inflow during the early Holocene, but this interpretation ... |
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