GRIP Deuterium Excess Reveals Rapid and Orbital-Scale Changes in Greenland Moisture Origin

Department of Geological Sciences, University of Colorado at Boulder, Boulder, Colorado, United States
Science (Impact Factor: 33.61). 08/2005; 309(5731):118-21. DOI: 10.1126/science.1108575
Source: PubMed


The Northern Hemisphere hydrological cycle is a key factor coupling ice sheets, ocean circulation, and polar amplification of climate change. Here we present a Northern Hemisphere deuterium excess profile covering one climatic cycle, constructed with the use of delta18O and deltaD Greenland Ice Core Project (GRIP) records. Past changes in Greenland source and site temperatures are quantified with precipitation seasonality taken into account. The imprint of obliquity is evidenced in the site-to-source temperature gradient at orbital scale. At the millennial time scale, GRIP source temperature changes reflect southward shifts of the geographical locations of moisture sources during cold events, and these rapid shifts are associated with large-scale changes in atmospheric circulation.

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Available from: James W. C. White, Oct 10, 2015
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    • "Determining the geographic reach and precise timing of these rapid climate fluctuations is essential for establishing both the dominant forcing mechanisms and the underlying oceaneatmosphere processes by which these climatic changes are propagated globally. Changes in oceanic circulation and ice cover at Contents lists available at ScienceDirect Quaternary Science Reviews high northern latitudes are commonly considered as the drivers of Quaternary climate change (Alley et al., 1993; Grootes et al., 1993; Weaver and Hughes, 1994; Masson-Delmotte et al., 2005a, 2005b). However, whilst the abrupt climate events of the last deglaciation are well defined in ice-core records from the polar regions of both hemispheres, their manifestation beyond the poles is less well constrained (Shakun and Carlson, 2010; Newnham et al., 2012; Petherick et al., 2013), with a particularly significant lack of representation of Southern Hemisphere records. "
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    ABSTRACT: Understanding the global response to millennial-scale climatic events is essential to our comprehension of climatic teleconnections and projection of future change, however the extent and nature of their expression in areas of the Southern Hemisphere is often viewed as equivocal. Here we report uranium–thorium dating of speleothem formations sampled at Sudwala Cave in the north-eastern Lowveld region of South Africa's summer rainfall zone (SRZ). The growth intervals of multiple formations, alongside a detailed chronology and multi-proxy analysis of two periods of growth, 40–35 ka and 13.8–12.8 ka, in a stalagmite (SC1), provide information regarding key fluctuations in the palaeoclimatic and palaeoenvironmental conditions during the Late Pleistocene. High-resolution stable isotope, trace element, and micro-Raman analysis are used alongside petrographic investigation to provide a detailed assessment of the climatic conditions associated with the onset and termination of growth in SC1. The combined Raman and petrographic analysis represents a rare approach, enabling the identification of aragonite–calcite shifts both within and across growth intervals and diagenetic events, potentially significantly influencing the recorded signal and often resulting in the major loss of chemical information. Consequently, the identification of this post-depositional chemical alteration could become a crucial prerequisite in speleothem palaeoclimatology, particularly in areas prone to aragonite speleothem deposition susceptible to calcite conversion, such as cave sites hosted by dolomitic karst systems. The multiple proxies used in this study highlight the complex forcing relationships between climatically related environmental change and local cave conditions on speleothem precipitation, contesting a common paradigm by associating drier conditions at Sudwala with the initiation of speleothem growth. The growth interval identified in stalagmite SC1 during the late deglaciation (13.85–12.79 ka) coincides convincingly with both the Southern Hemispherically-Forced Antarctic Cold Reversal (14.1–12.8 ka), and the Younger Dryas (12.9–11.5 ka) of Northern Hemispheric origin, identifying Southern Africa as a vital location for the investigation of the hemispheric to global expression of the millennial-scale fluctuations of the last deglaciation.
    Quaternary Science Reviews 02/2015; 110. DOI:10.1016/j.quascirev.2014.11.016 · 4.57 Impact Factor
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    • "Qualitative temperature reconstructions are available from stable water isotope (δ 18 O, δD) measurements along polar ice cores. However, quantitative temperature estimates based on the relationship between δ 18 O and temperature are limited for Greenland ice due to the influence of precipitation seasonality and source temperature changes (Krinner et al., 1997; Boyle, 1997; Masson-Delmotte et al., 2005). The isotopic composition of nitrogen trapped in air bubbles in the ice quantitatively constrains the magnitude of the fast temperature increases (Severinghaus et al., 1998; Severinghaus and Brook, 1999; Lang et al., 1999). "
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    ABSTRACT: During the last glacial cycle, Greenland temperature showed many rapid temperature variations, the so called Dansgaard-Oeschger (DO) events. The past atmospheric methane concentration closely followed these temperature variations, which implies that the warmings recorded in Greenland were probably hemispheric in extent. Here we substantially extend and complete the North Greenland Ice Core Project (NGRIP) methane record from Termination 1 back to the end of the last interglacial period with a mean time resolution of 54 yr. We relate the amplitudes of the methane increases associated with DO events to the amplitudes of the NGRIP temperature increases derived from stable nitrogen isotope (δ15N) measurements, which have been performed along the same ice core. We find the sensitivity to oscillate between 5 parts per billion by volume (ppbv) per °C and 18 ppbv °C-1 with the approximate frequency of the precessional cycle. A remarkably high sensitivity of 25.5 ppbv °C-1 is reached during Termination 1. Analysis of the timing of the fast methane and temperature increases reveals significant lags of the methane increases relative to NGRIP temperature for the DO events 5, 9, 10, 11, 13, 15, 19, and 20. We further show that the relative interpolar concentration difference of methane is 4.6 ± 0.7% between the DO events 18 and 19 and 4.4 ± 0.8% between the DO events 19 to 20, which is in the same order as in the stadials before and after DO event 2 around the Last Glacial Maximum.
    Climate of the Past Discussions 08/2013; 9(4):4655-4704. DOI:10.5194/cpd-9-4655-2013
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    • "The enhancement of the source–site temperature gradient enhances isotopic distillation and produces precipitation with lower δ 18 O levels during cold periods, increasing α. Contradicting earlier assumptions (Boyle, 1997), conceptual distillation models constrained by GRIP deuterium excess data suggest that this effect is most probably secondary (Masson-Delmotte et al., 2005). "
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    ABSTRACT: Air and water stable isotope measurements from four Greenland deep ice cores (GRIP, GISP2, NGRIP and NEEM) are investigated over a series of Dansgaard– Oeschger events (DO 8, 9 and 10), which are representative of glacial millennial scale variability. Combined with firn modeling, air isotope data allow us to quantify abrupt temperature increases for each drill site (1σ = 0.6 °C for NEEM, GRIP and GISP2, 1.5 °C for NGRIP). Our data show that the magnitude of stadial–interstadial temperature increase is up to 2 °C larger in central and North Greenland than in north-west Greenland: i.e., for DO 8, a magnitude of +8.8 °C is inferred, which is significantly smaller than the +11.1 °C inferred at GISP2. The same spatial pattern is seen for accumulation increases. This pattern is coherent with climate simulations in response to reduced sea-ice extent in the Nordic seas. The temporal water isotope (δ18O)–temperature relationship varies between 0.3 and 0.6 (±0.08) ‰ °C −1 and is systematically larger at NEEM, possibly due to limited changes in precipitation seasonality compared to GISP2, GRIP or NGRIP. The gas age−ice age difference of warming events represented in water and air isotopes can only be modeled when assuming a 26 % (NGRIP) to 40 % (GRIP) lower ac-cumulation than that derived from a Dansgaard–Johnsen ice flow model.
    Climate of the Past 05/2013; 9(3):1029-1051. DOI:10.5194/cp-9-1029-2013 · 3.38 Impact Factor
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