Delayed build-up of Arctic ice sheets during 400,000-year minima in insolation variability

Abstract

Knowledge of the past variability of climate at high northern latitudes during astronomical analogues of the present interglacial may help to inform our understanding of future climate change. Unfortunately, long-term continuous records of ice-sheet variability in the Northern Hemisphere only are scarce because records of benthic (18)O content represent an integrated signal of changes in ice volume in both polar regions. However, variations in Northern Hemisphere ice sheets influence the Siberian High (an atmospheric pressure system), so variations in the East Asian winter monsoon (EAWM)--as recorded in the aeolian dust deposits on the Chinese Loess Plateau--can serve as a useful proxy of Arctic climate variability before the ice-core record begins. Here we present an EAWM proxy record using grain-size variations in two parallel loess sections representative of sequences across the whole of the Chinese Loess Plateau over the past 900,000 years. The results show that during periods of low eccentricity and precessional variability at approximately 400,000-year intervals, the grain-size-inferred intensity of the EAWM remains weak for up to 20,000 years after the end of the interglacial episode of high summer monsoon activity and strong pedogenesis. In contrast, there is a rapid increase in the EAWM after the end of most other interglacials. We conclude that, for both the 400,000-year interglacials, the weak EAWM winds maintain a mild, non-glacial climate at high northern latitudes for much longer than expected from the conventional loess and marine oxygen isotope records. During these times, the less-severe summer insolation minima at 65° N (ref. 4) would have suppressed ice and snow accumulation, leading to a weak Siberian High and, consequently, weak EAWM winds.

Long-term Pleistocene aridification and possible linkage to high-latitude forcing: New evidence from grain size and magnetic susceptibility proxies from loess-paleosol record in northeastern China

“…The content of the N 30 μm grains is believed to be more strongly associated with the strength of the East Asian winter monsoon (EAWM) (Lu et al, 1999). This calibrated chronology is thought to be more reliable than that obtained by linear interpolation because assumed changes in dust accumulation rate are considered in the age model (Hao et al, 2012). As illustrated in Fig.…”

“…However, it is clear that, based on this initial chronology, there are some phase differences for the NYZG section and the benthic δ 18 O record, and this may hamper both a detailed analysis of the evolution of the regional climate and comparison with other paleoclimatic proxy records. Here, we use the traditional age model derivation approach based on the correlation of Chinese loess-palaeosol sequences with the benthic δ 18 O record to refine the initial chronology (Ding et al, 1994;Hao et al, 2012;Heslop et al, 2000;Kukla, 1987;Wu et al, 2005). In this approach, the MS maxima (minima) are directly correlated to the interglacial (glacial) stages represented by the lower (higher) values of benthic δ 18 O.…”

Danube loess stratigraphy — Towards a pan-European loess stratigraphic model

“…In the following discussion, we apply the unified stratigraphy of the DLPS for a direct correlation of two very distant loess regions, the Danube loess region, represented by the composite type sequence MSS, and the CLPS represented by the type sequence of Luochuan (e.g. Kukla and an, 1989;Hao et al, 2012). …”

“…Figures 5 and 17 show the correlation between the MSS loess-palaeosol type sequence and the equivalent for the Chinese loess at Luochuan (Liu et al, 1985;Hao et al, 2012). Below we suggest that the loess chronostratigraphies in the Vojvodina region and in the central CLP from S0 to L9, correspond strongly.…”

On the importance of grain size in luminescence dating using quartz

“…MST is the laboratory code used at the Mostistea section from the Romanian Plain Timar-Gabor et al, 2012). CST samples were taken from Costineş ti section near the Black Sea shore (Timar-Gabor and Wintle, 2013;Constantin et al, 2014), samples coded as LCA come from Lunca section in South Western Romania , samples coded as ORL are quartz extracts from Serbian loess , samples coded with XF come from Xifeng section in the Chinese loess plateau (Hao et al, 2012(Hao et al, , 2015 (see details in the supplementary material), while sample coded as RUH comes from Ruhama desert loess section in Israel (Wieder et al, 2008). In addition, samples with an origin other than loess were investigated.…”