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Evidence for ephemeral middle Eocene to early Oligocene Greenland glacial ice and pan-Arctic sea ice ArchiMer
Tripati, Aradhna; Darby, Dennis.
Earth's modern climate is defined by the presence of ice at both poles, but that ice is now disappearing. Therefore understanding the origin and causes of polar ice stability is more critical than ever. Here we provide novel geochemical data that constrain past dynamics of glacial ice on Greenland and Arctic sea ice. Based on accurate source determinations of individual ice-rafted Fe-oxide grains, we find evidence for episodic glaciation of distinct source regions on Greenland as far-ranging as similar to 68 degrees N and similar to 80 degrees N synchronous with ice-rafting from circum-Arctic sources, beginning in the middle Eocene. Glacial intervals broadly coincide with reduced CO2, with a potential threshold for glacial ice stability near similar to 500...
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Ano: 2018 URL: https://archimer.ifremer.fr/doc/00434/54587/55976.pdf
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A robust, multisite Holocene history of drift ice off northern Iceland: implications for North Atlantic climate ArchiMer
Andrews, John T.; Darby, Dennis; Eberle, Dennis; Jennings, Anne E.; Moros, Matthias; Ogilvie, Astrid.
An important indicator of Holocene climate change is provided by evidence for variations in the extent of drift ice. A proxy for drift ice in Iceland waters is provided by the presence of quartz. Quantitative x-ray diffraction analysis of the < 2 mm sediment fraction was undertaken on 16 cores from around Iceland. The quartz weight (wt.)% estimates from each core were integrated into 250-yr intervals between -0.05 and 11.7 cal. ka BP. Median quartz wt.% varied between 0.2 and 3.4 and maximum values ranged between 2.8 and 11.8 wt.%. High values were attained in the early Holocene and minimum values were reached 6 7 cal. ka BP. Quartz wt.% then rose steadily during the late Holocene. Our data exhibit no correlation with counts on haematite-stained quartz...
Tipo: Text Palavras-chave: Ice rafted debris; Iceland; Quartz; Drift ice; Holocene; Arctic basin.
Ano: 2009 URL: https://archimer.ifremer.fr/doc/00218/32943/31420.pdf
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