A penultimate glacial monsoon record from Hulu Cave and two-phase glacial terminations
TL;DR: Oxygen isotope records of three stalagmites from Hulu Cave, China, extend the previous high-resolution absolute-dated Hulu Asian Monsoon record from the last to the penultimate glacial and deglacial periods as discussed by the authors.
Abstract: Oxygen isotope records of three stalagmites from Hulu Cave, China, extend the previous high-resolution absolute-dated Hulu Asian Monsoon record from the last to the penultimate glacial and deglacial periods. The penultimate glacial monsoon broadly follows orbitally induced insolation variations and is punctuated by at least 16 millennial-scale events. We confirm a Weak Monsoon Interval between 135.5 ± 1.0 and 129.0 ± 1.0 ka, prior to the abrupt increase in monsoon intensity at Asian Monsoon Termination II. Based on correlations with both marine ice-rafted debris and atmospheric CH 4 records, we demonstrate that most of marine Termination II, the full rise in Antarctic temperature and atmospheric CO 2 , and much of the rise in CH 4 occurred within the Weak Monsoon Interval, when the high northern latitudes were probably cold. From these relationships and similar relationships observed for Termination I, we identify a two-phase glacial termination process that was probably driven by orbital forcing in both hemispheres, affecting the atmospheric hydrological cycle, and combined with ice sheet dynamics.
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TL;DR: An absolute-dated oxygen isotope record from Sanbao cave, central China, is presented that completes a Chinese-cave-based record of the strength of the East Asian monsoon that covers the past 224,000 years, supporting the idea that tropical/subtropical monsoons respond dominantly and directly to changes in Northern Hemisphere summer insolation on orbital timescales.
Abstract: Stalactites, stalagmites and the many other forms of mineral deposits found in caves are a mainstay of climate studies, recording oxygen isotope ratios in limestone laid down over time. That pattern links to the water temperature of ancient oceans, and thus to climate. A new oxygen isotope record from Sanbao Cave, central China, tells the story of the region's climate stretching back 200,000 years, filling gaps in the record of a particularly important climate event, the East Asian monsoon. High-resolution speleothem records from China have provided insights into the factors that control the strength of the East Asian monsoon1,2,3,4. Our understanding of these factors remains incomplete, however, owing to gaps in the record of monsoon history over the past two interglacial–glacial cycles. In particular, missing sections have hampered our ability to test ideas about orbital-scale controls on the monsoon5,6,7, the causes of millennial-scale events8,9 and relationships between changes in the monsoon and climate in other regions. Here we present an absolute-dated oxygen isotope record from Sanbao cave, central China, that completes a Chinese-cave-based record of the strength of the East Asian monsoon that covers the past 224,000 years. The record is dominated by 23,000-year-long cycles that are synchronous within dating errors with summer insolation at 65° N (ref. 10), supporting the idea that tropical/subtropical monsoons respond dominantly and directly to changes in Northern Hemisphere summer insolation on orbital timescales5. The cycles are punctuated by millennial-scale strong-summer-monsoon events (Chinese interstadials1), and the new record allows us to identify the complete series of these events over the past two interglacial–glacial cycles. Their duration decreases and their frequency increases during glacial build-up in both the last and penultimate glacial periods, indicating that ice sheet size affects their character and pacing. The ages of the events are exceptionally well constrained and may thus serve as benchmarks for correlating and calibrating climate records.
1,603 citations
Cites background from "A penultimate glacial monsoon recor..."
...Our data further indicate that (1) the duration and frequency of the millennial-scale events change systematically throughout the course of a glacial period, and (2) that the general nature of these changes is reproducible for the last two glacial periods....
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TL;DR: The sign of the correlation between the AM and temperature switches around 1960 is suggested, suggesting that anthropogenic forcing superseded natural forcing as the major driver of AM changes in the late 20th century.
Abstract: A record from Wanxiang Cave, China, characterizes Asian Monsoon (AM) history over the past 1810 years. The summer monsoon correlates with solar variability, Northern Hemisphere and Chinese temperature, Alpine glacial retreat, and Chinese cultural changes. It was generally strong during Europe's Medieval Warm Period and weak during Europe's Little Ice Age, as well as during the final decades of the Tang, Yuan, and Ming Dynasties, all times that were characterized by popular unrest. It was strong during the first several decades of the Northern Song Dynasty, a period of increased rice cultivation and dramatic population increase. The sign of the correlation between the AM and temperature switches around 1960, suggesting that anthropogenic forcing superseded natural forcing as the major driver of AM changes in the late 20th century.
861 citations
TL;DR: Variability of the Asian Monsoon over the past 400,000 years correlates with the ends of glacial periods, and AM records for the past four glacial terminations can be precisely correlated with those from ice cores and marine sediments, establishing the timing and sequence of major events.
Abstract: 230Th-dated oxygen isotope records of stalagmites from Sanbao Cave, China, characterize Asian Monsoon (AM) precipitation through the ends of the third- and fourthmost recent ice ages. As a result, AM records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments, establishing the timing and sequence of major events. In all four cases, observations are consistent with a classic Northern Hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets. Meltwater and icebergs entering the North Atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon, causing increases in atmospheric CO2 and Antarctic temperatures that drive the termination in the Southern Hemisphere. Increasing CO2 and summer insolation drive recession of northern ice sheets, with probable positive feedbacks between sea level and CO2.
782 citations
TL;DR: In this paper, a process-based summary of the multiple controls on speleothem oxygen-isotope values (d 18 O) in the atmosphere, soil, epikarst, and calcite, illustrated with case studies is presented.
615 citations
Additional excerpts
...…cool periods apparently coincident with Heinrich events, high d18O values may indicate a greater contribution of winter rainfall and are associated with wet periods in the southern hemisphere neo-tropics (Wang et al., 2004), an idea that has support from modeling studies (Chiang et al., 2003)....
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TL;DR: In this paper, the authors used a numerical climate model with an embedded oxygen-isotope model to assess what caused the shifts in the oxygen isotope signature of precipitation during a climate perturbation designed to mimic a Heinrich event.
Abstract: Carbonate cave deposits in India and China are assumed to record the intensity of monsoon precipitation, because the 18 O of the carbonate tracks the isotopic signature of precipitation. These records show spatially coherent variability throughout the last ice age and suggest that monsoon strength was altered during the millennial-scale climate variations known as Dansgaard‐Oeschger events and during the Heinrich cooling events. Here we use a numerical climate model with an embedded oxygen-isotope model to assess what caused the shifts in the oxygen-isotope signature of precipitation during a climate perturbation designed to mimic a Heinrich event. Our simulations show that a sudden increase in North Atlantic sea-ice extent during the last glacial period leads to cooling in the Northern Hemisphere, reduced precipitation over the Indian basin and weakening of the Indian monsoon. The precipitation is isotopically heavier over India and the water vapour exported to China is isotopically enriched. Our model broadly reproduces the enrichment of 18 O over Northern India and East Asia evident in speleothem records during Heinrich events. We therefore conclude that changes in the 18 O of cave carbonates associated with Heinrich events reflect changes in the intensity of Indian rather than East Asian monsoon precipitation.
501 citations
Cites background from "A penultimate glacial monsoon recor..."
...A change in δ 18 O p may result from a change in several local and non-local processes, including: the ratio of summer-to-spring precipitation (seasonality of precipitation affects δ 18 O p because summer rainfall has lighter—that is, more negative— δ 18 O values compared with spring precipitatio...
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References
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01 Jan 2013
TL;DR: The recent completion of drilling at Vostok station in East Antarctica has allowed the extension of the ice record of atmospheric composition and climate to the past four glacial-interglacial cycles.
Abstract: The recent completion of drilling at Vostok station in East Antarctica has allowed the extension of the ice record of atmospheric composition and climate to the past four glacial–interglacial cycles. The succession of changes through each climate cycle and termination was similar, and atmospheric and climate properties oscillated between stable bounds. Interglacial periods differed in temporal evolution and duration. Atmospheric concentrations of carbon dioxide and methane correlate well with Antarctic air-temperature throughout the record. Present-day atmospheric burdens of these two important greenhouse gases seem to have been unprecedented during the past 420,000 years.
5,469 citations
TL;DR: The recent completion of drilling at Vostok station in East Antarctica has allowed the extension of the ice record of atmospheric composition and climate to the past four glacial-interglacial cycles as discussed by the authors.
Abstract: The recent completion of drilling at Vostok station in East Antarctica has allowed the extension of the ice record of atmospheric composition and climate to the past four glacial–interglacial cycles. The succession of changes through each climate cycle and termination was similar, and atmospheric and climate properties oscillated between stable bounds. Interglacial periods differed in temporal evolution and duration. Atmospheric concentrations of carbon dioxide and methane correlate well with Antarctic air-temperature throughout the record. Present-day atmospheric burdens of these two important greenhouse gases seem to have been unprecedented during the past 420,000 years.
5,109 citations
TL;DR: In this paper, the authors present a detailed stable isotope record for the full length of the Greenland Ice-core Project Summit ice core, extending over the past 250 kyr according to a calculated timescale, and find that climate instability was not confined to the last glaciation, but appears also have been marked during the last interglacial (as explored more fully in a companion paper), and during the previous Saale-Holstein glacial cycle.
Abstract: RECENT results1,2 from two ice cores drilled in central Greenland have revealed large, abrupt climate changes of at least regional extent during the late stages of the last glaciation, suggesting that climate in the North Atlantic region is able to reorganize itself rapidly, perhaps even within a few decades. Here we present a detailed stable-isotope record for the full length of the Greenland Ice-core Project Summit ice core, extending over the past 250 kyr according to a calculated timescale. We find that climate instability was not confined to the last glaciation, but appears also to have been marked during the last interglacial (as explored more fully in a companion paper3) and during the previous Saale–Holstein glacial cycle. This is in contrast with the extreme stability of the Holocene, suggesting that recent climate stability may be the exception rather than the rule. The last interglacial seems to have lasted longer than is implied by the deep-sea SPECMAP record4, in agreement with other land-based observations5,6. We suggest that climate instability in the early part of the last interglacial may have delayed the melting of the Saalean ice sheets in America and Eurasia, perhaps accounting for this discrepancy.
4,367 citations
TL;DR: The record links North Atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer East Asian Monsoon originates and generally agrees with the timing of temperature changes from the Greenland Ice Sheet Project Two (GISP2).
Abstract: Oxygen isotope records of five stalagmites from Hulu Cave near Nanjing bear a remarkable resemblance to oxygen isotope records from Greenland ice cores, suggesting that East Asian Monsoon intensity changed in concert with Greenland temperature between 11,000 and 75,000 years before the present (yr. B.P.). Between 11,000 and 30,000 yr. B.P., the timing of changes in the monsoon, as established with 230Th dates, generally agrees with the timing of temperature changes from the Greenland Ice Sheet Project Two (GISP2) core, which supports GISP2's chronology in this interval. Our record links North Atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer East Asian Monsoon originates.
2,759 citations
TL;DR: A hydraulic model of the water exchange between the Red Sea and the world ocean is used to derive the sill depth—and hence global sea level—over the past 470,000 years, finding that sea-level changes of up to 35 m occurred, coincident with abrupt changes in climate.
Abstract: The last glacial cycle was characterized by substantial millennial-scale climate fluctuations1,2,3,4,5, but the extent of any associated changes in global sea level (or, equivalently, ice volume) remains elusive. Highstands of sea level can be reconstructed from dated fossil coral reef terraces6,7, and these data are complemented by a compilation of global sea-level estimates based on deep-sea oxygen isotope ratios at millennial-scale resolution8 or higher1. Records based on oxygen isotopes, however, contain uncertainties in the range of ±30 m, or ±1 °C in deep sea temperature9,10. Here we analyse oxygen isotope records from Red Sea sediment cores to reconstruct the history of water residence times in the Red Sea. We then use a hydraulic model of the water exchange between the Red Sea and the world ocean to derive the sill depth—and hence global sea level—over the past 470,000 years (470 kyr). Our reconstruction is accurate to within ±12 m, and gives a centennial-scale resolution from 70 to 25 kyr before present. We find that sea-level changes of up to 35 m, at rates of up to 2 cm yr-1, occurred, coincident with abrupt changes in climate.
1,485 citations