On the glacial-interglacial variability of the Asian monsoon in speleothem δ18O records.
TL;DR: It is found that the records close to the monsoon moisture source show large glacial-interglacial variability, which then decreases landward, the moisture transport pathway effect, which counteracts the forcing of glacial boundary conditions.
Abstract: While Asian monsoon (AM) changes have been clearly captured in Chinese speleothem oxygen isotope (δ18O) records, the lack of glacial-interglacial variability in the records remains puzzling. Here, we report speleothem δ18O records from three locations along the trajectory of the Indian summer monsoon (ISM), a major branch of the AM, and characterize AM rainfall over the past 180,000 years. We have found that the records close to the monsoon moisture source show large glacial-interglacial variability, which then decreases landward. These changes likely reflect a stronger oxygen isotope fractionation associated with progressive rainout of AM moisture during glacial periods, possibly due to a larger temperature gradient and suppressed plant transpiration. We term this effect, which counteracts the forcing of glacial boundary conditions, the moisture transport pathway effect.
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TL;DR: In this article, Wang et al. reconcile the Chinese 100 kyr problem and the sea-land precession phase paradox by comparing the results of different hydroclimatic proxies.
Abstract: The Asian summer monsoon (ASM) is a vast climate system, whose variability is critical to the livelihoods of billions of people across the Asian continent. During the past half-century, much progress has been made in understanding variations on a wide range of timescales, yet several significant issues remain unresolved. Of note are two long-standing problems concerning orbital-scale variations of the ASM. (1) Chinese loess magnetic susceptibility records show a persistent glacial-interglacial dominated ~100 kyr (thousand years) periodicity, while the cave oxygen-isotope (δ18O) records reveal periodicity in an almost pure precession band (~20 kyr periodicity)—the “Chinese 100 kyr problem”. (2) ASM records from the Arabian Sea and other oceans surrounding the Asian continent show a significant lag of 8–10 kyr to Northern Hemisphere summer insolation (NHSI), whereas the Asian cave δ18O records follow NHSI without a significant lag—a discrepancy termed the “sea-land precession-phase paradox”. How can we reconcile these differences? Recent and more refined model simulations now provide spatial patterns of rainfall and wind across the precession cycle, revealing distinct regional divergences in the ASM domain, which can well explain a large portion of the disparities between the loess, marine, and cave proxy records. Overall, we also find that the loess, marine, and cave records are indeed complementary rather than incompatible, with each record preferentially describing a certain aspect of ASM dynamics. Our study provides new insight into the understanding of different hydroclimatic proxies and largely reconciles the “Chinese 100 kyr problem“ and “sea-land precession-phase paradox”.
50 citations
24 citations
Ritsumeikan University1, University of Newcastle2, Free University of Berlin3, University of Oxford4, University of Glasgow5, University of Derby6, Aberystwyth University7, Trinity College, Dublin8, Osaka City University9, Chiba University of Commerce10, Nagoya University11, University of Groningen12, Naruto University of Education13, University of Tokyo14
TL;DR: In this article, the authors present new pollen data and mean annual temperature reconstruction from the annually laminated sediments of Lake Suigetsu, Japan, which is an integral component of the IntCal20 radiocarbon calibration model, in which the absolute age scale is established to the highest standard.
18 citations
TL;DR: In this paper, the authors presented a high-resolution EASM precipitation record reconstructed from the loess redness in North China over the past 720 kyr, showing that the average precipitation for interglacials is 420mm/yr, higher than present (~280 mm/yr).
Abstract: The periodicity and forcing mechanism of the past East Asian summer monsoon (EASM) precipitation are the natural background for predicting future precipitation changes, but they are controversial and intensely debated. Here, we present a high-resolution EASM precipitation record reconstructed from the loess redness in North China over the past 720 kyr. The average precipitation for interglacials is 420 mm/yr, higher than present (~280 mm/yr). Combing through our EASM records and previously published data exhibits a dominated periodicity of 100 kyr on the orbital timescale, and thus supports the hypothesis of high-latitude climate forcing. More importantly, we found the precession cycle appears only after the Mid-Brunhes Transition (MBT, ~430 ka) in the EASM records and it follows the global ice volume prior to the MBT in the interglacials interiors. We argue that during the post-MBT interglacials, abruptly appearing Arctic perennial sea ice resulted southward shift of the Northern Hemisphere Westerlies jet, thereby decreasing the EASM precipitation in North China. This suggests that the precession rhythm in the EASM possibly is a result of Arctic perennial sea ice or Northern Hemisphere ice sheets changes. In the warm Marine Isotope Stages (MIS) 5e and 11e, the strongest EASM precipitation may be related to the strengthening of the moisture transport from the warming tropical ocean. Therefore, the variation of the mid-latitude EASM precipitation intensity during the interglacial interiors is the integrated effect between the North Hemisphere high latitude ice volume and low latitude climate changes.
15 citations
TL;DR: In this article, the authors quantitatively deconvolve these parameters affecting δ18OCc by applying three geochemical techniques in speleothems covering the penultimate glacial termination, and reveal that the different modes of the AMOC produced distinct impacts on the monsoon system.
Abstract: During glacial terminations, massive iceberg discharges and meltwater pulses in the North Atlantic triggered a shutdown of the Atlantic Meridional Overturning Circulation (AMOC). Speleothem calcium carbonate oxygen isotope records (δ18OCc) indicate that the collapse of the AMOC caused dramatic changes in the distribution and variability of the East Asian and Indian monsoon rainfall. However, the mechanisms linking changes in the intensity of the AMOC and Asian monsoon δ18OCc are not fully understood. Part of the challenge arises from the fact that speleothem δ18OCc depends on not only the δ18O of precipitation but also temperature and kinetic isotope effects. Here we quantitatively deconvolve these parameters affecting δ18OCc by applying three geochemical techniques in speleothems covering the penultimate glacial termination. Our data suggest that the weakening of the AMOC during meltwater pulse 2A caused substantial cooling in East Asia and a shortening of the summer monsoon season, whereas the collapse of the AMOC during meltwater pulse 2B (133,000 years ago) also caused a dramatic decrease in the intensity of the Indian summer monsoon. These results reveal that the different modes of the AMOC produced distinct impacts on the monsoon system. The influence of meltwater pulse events on Asian monsoon systems varied in line with the degree of AMOC weakening, according to a multi-proxy analysis of speleothems from China covering the penultimate glacial termination.
11 citations
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TL;DR: The authors used stable isotope records from a sediment core off the Malabar coast in the southeastern Arabian Sea with centennial-scale resolution to test this hypothesis and to constrain the nature and timing of deglacial climate change in the tropical Indian Ocean.
143 citations
TL;DR: In this article, the authors provided the first continuous measurements of isotopic composition (δD and δ18O) of water vapor over the subtropical Eastern North Atlantic Ocean from mid-August to mid-September 2012.
Abstract: We provide the first continuous measurements of isotopic composition (δD and δ18O) of water vapor over the subtropical Eastern North Atlantic Ocean from mid-August to mid-September 2012. The ship was located mostly around 26°N, 35°W where evaporation exceeded by far precipitation and water vapor at 20 m largely originated from surface evaporation. The only large deviations from that occurred during a 2 day period in the vicinity of a weak low-pressure system. The continuous measurements were used to investigate deuterium excess (d-excess) relation to evaporation. During 25 days d-excess was negatively correlated with relative humidity (r2 = 0.89). Moreover, d-excess estimated in an evaporative model with a closure assumption reproduced most of the observed variability. From these observations, the d-excess parameter seems to be a good indicator of evaporative conditions. We also conclude that in this region, d-excess into the marine boundary layer is less affected by mixing with the free troposphere than the isotopic composition. From our data, the transition from smooth to rough regime at the ocean surface is associated with a d-excess decrease of 5‰, which suggests the importance of the ocean surface roughness in controlling d-excess in this region.
130 citations
TL;DR: In this paper, the discrepancy between central Greenland borehole temperatures and the isotopic composition of Last Glacial Maximum ice can be explained by a shift in the •5180-T relationship for the hydrological cycle linked to cooler tropical temperatures.
Abstract: The discrepancy between central Greenland borehole temperatures and the isotopic composition of Last Glacial Maximum ice can be explained by a shift in the •5180-T relationship for the hydrological cycle linked to cooler tropical temperatures. This concept is illustrated using a simple Rayleigh distillation model. An estimate for o•=A•5180/AT (LGM-Holocene) of-0.37 %o/oC is determined with a simple graphical technique.
129 citations
TL;DR: This article used a global compilation of 49 paired sea surface temperature-planktonic δ 18 O records to extract the mean of surface ocean seawater over the past 800 kyr, which they interpret to dominantly reflect global ice volume.
125 citations
TL;DR: In this article, a high-resolution record of East Asian air temperature over the past 130,000 years, based on soil bacterial lipid signatures preserved in a loess-paleosol sequence from the Mangshan loess plateau in China, was reported.
116 citations