کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5779589 1634677 2017 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Tropical and high latitude forcing of enhanced megadroughts in Northern China during the last four terminations
ترجمه فارسی عنوان
تحریم گرمسیری و بلند پروازانه باعث افزایش قاچاق مواد منفجره در شمال چین در طی چهار جلسه اخیر شد
کلمات کلیدی
خشکی، بیومارکرهای میکروبی، تعطیلات یخبندان، موزن آسیایی،
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علوم زمین و سیاره ای (عمومی)
چکیده انگلیسی
Understanding the origin and evolutionary history of drought events is of great significance, providing critical insight into future hydrological conditions under the changing climate. Due to the scarcity of drought proxies from northern China, the occurrence and underlying mechanisms of the drought events remains enigmatic on longer timescales. Here we utilize microbial lipid proxies to reconstruct significant drought events over the last four ice age terminations in the southernmost section (Weinan section) of the Chinese Loess Plateau. The abundance of archaeal isoprenoid GDGTs (glycerol dialkyl glycerol tetraethers) relative to bacterial branched GDGTs, measured by Ri/b and BIT indices, is diagnostic of enhanced drought conditions. The Ri/b (and BIT) indices are stable and low (high) throughout most of the loess section spanning the last 350 thousand years, but they do exhibit sharp transient peaks (valleys) during the intervals associated with the four ice age terminations, and especially Terminations II and IV. These enhanced drought events are, non-intuitively, associated with a significant decrease in the relative abundance of C4 plants, inferred by a decrease in the carbon isotope composition of bulk organic matter. Although the microbial records show some consistency with the Weinan grain size profiles, indicative of Eastern Asian winter monsoon variability, they also show some apparent difference. In fact, some features of the microbial records exhibit strong similarities with marine sediment planktonic foraminiferal δ13C records from the western Pacific warm pool, which reflect ENSO-like changes during glacial terminations. Therefore, enhanced droughts immediately before the interglacial warming in northern China could be explained, at least in part, by teleconnections in tropical ocean-atmosphere circulation via shifts in the Intertropical Convergence Zone (ITCZ) and associated Jet Stream over the Asian continent. According to our microbial biomarker data, these enhanced megadroughts are apparently different, both in terms of severity and causal mechanism, from the more commonly discussed dry conditions observed during glacial periods.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 479, 1 December 2017, Pages 98-107
نویسندگان
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