Global atmospheric teleconnections during Dansgaard–Oeschger events

Markle, B. R.; Steig, Eric J.; Buizert, Christo; Schoenemann, Spruce W.; Bitz, Cecilia M.; Fudge, T. J.; Pedro, J. B.; Ding, Qinghua; Jones, Tyler R.; White, James W. C.; Sowers, Todd

doi:10.1038/ngeo2848

Cited by 127 publications

(173 citation statements)

References 38 publications

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“…(4) Yet interlab reproducibility (INSTAAR CRDS-CFA vs. UW CRDS) of down-sampled dxs has a low R 2 value of 0.29, but still within the same range of values between ∼ 1 and 4 ‰. These results suggest that the inherent noise in dxs measurements may make this parameter most useful at timescales of centuries to millennia when the range of WDC dxs increases to ∼ 0 to 12 ‰ (Markle et al, 2017).…”

Section: Wais Divide Ice Core Testsmentioning

confidence: 76%

Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores

et al. 2017

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Abstract. Water isotopes in ice cores are used as a climate proxy for local temperature and regional atmospheric circulation as well as evaporative conditions in moisture source regions. Traditional measurements of water isotopes have been achieved using magnetic sector isotope ratio mass spectrometry (IRMS). However, a number of recent studies have shown that laser absorption spectrometry (LAS) performs as well or better than IRMS. The new LAS technology has been combined with continuous-flow analysis (CFA) to improve data density and sample throughput in numerous prior ice coring projects. Here, we present a comparable semiautomated LAS-CFA system for measuring high-resolution water isotopes of ice cores. We outline new methods for partitioning both system precision and mixing length into liquid and vapor components -useful measures for defining and improving the overall performance of the system. Critically, these methods take into account the uncertainty of depth registration that is not present in IRMS nor fully accounted for in other CFA studies. These analyses are achieved using samples from a South Pole firn core, a Greenland ice core, and the West Antarctic Ice Sheet (WAIS) Divide ice core. The measurement system utilizes a 16-position carousel contained in a freezer to consecutively deliver ∼ 1 m × 1.3 cm 2 ice sticks to a temperature-controlled melt head, where the ice is converted to a continuous liquid stream and eventually vaporized using a concentric nebulizer for isotopic analysis. An integrated delivery system for water isotope standards is used for calibration to the Vienna Standard Mean Ocean Water (VSMOW) scale, and depth registration is achieved using a precise overhead laser distance device with an uncertainty of ±0.2 mm. As an added check on the system, we perform inter-lab LAS comparisons using WAIS Divide ice samples, a corroboratory step not taken in prior CFA studies. The overall results are important for substantiating data obtained from LAS-CFA systems, including optimizing liquid and vapor mixing lengths, determining melt rates for ice cores with different accumulation and thinning histories, and removing system-wide mixing effects that are convolved with the natural diffusional signal that results primarily from water molecule diffusion in the firn column.

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Section: Wais Divide Ice Core Testsmentioning

confidence: 76%

Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores

et al. 2017

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“…This could be explained by an important contribution of sublimated moisture with kinetic fractionation. Additionally, the significant negative correlation between d ln and δ 18 O in summer precipitation on the East Antarctic Plateau (Figure c) should indicate the effect of kinetic fractionation during sublimation because the influences of equilibrium fractionation and kinetic fractionation during snow formation on deuterium excess are eliminated by the logarithmic definition (Markle et al, ; Schoenemann et al, ; Schoenemann & Steig, ; Uemura et al, ). When the δ 18 O is lower (corresponding to lower temperature and RH), stronger kinetic fractionation during sublimation is expected, and vice versa.…”

Section: Discussionmentioning

confidence: 99%

“…The second‐order parameters of δD, δ 18 O, and δ 17 O, d‐excess and 17 O‐excess, defined as d‐excess = δD − 8 × δ 18 O (Dansgaard, ) and 17 O‐excess = ln(δ 17 O + 1) − 0.528 × ln(δ 18 O + 1) (Barkan & Luz, ; Landais et al, ; Luz & Barkan, ), can preserve a climatic signal from the moisture source region (Angert et al, ; Johnsen et al, ; Jouzel et al, ; Jouzel et al, ; Landais et al, ; Masson‐Delmotte et al, ; Markle et al, ; Merlivat & Jouzel, ; Uemura et al, ; Vimeux et al, , ), imprinted by kinetic fractionation of water stable isotopes during evaporation. The d‐excess is mainly controlled by the sea surface temperature (SST) and/or relative humidity (RH) at the moisture source region (Merlivat & Jouzel, ; Steen‐Larsen, Sveinbjörnsdottir, et al, ; Uemura et al, ), though the effect of SST has been questioned by direct observations of water stable isotopes in water vapor in the marine boundary layer (Steen‐Larsen et al, , ).…”

Section: Introductionmentioning

confidence: 99%

Influence of Summer Sublimation on δD, δ¹⁸O, and δ¹⁷O in Precipitation, East Antarctica, and Implications for Climate Reconstruction From Ice Cores

et al. 2019

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In central Antarctica, where accumulation rates are very low, summer sublimation of surface snow is a key element of the surface mass balance, but its fingerprint in isotopic composition of water (δD, δ18O, and δ17O) remains unclear. In this study, we examined the influence of summer sublimation on δD, δ18O, and δ17O in precipitation using data sets of isotopic composition of precipitation at various sites on the inland East Antarctica. We found unexpectedly low δ18O values in the summer precipitation, decoupled from surface air temperatures. This feature can be explained by the combined effects of weak or nonexistent temperature inversion and moisture recycling associated with sublimation‐condensation processes in summer. Isotopic fractionation during the moisture‐recycling process also explains the observed high values of d‐excess and 17O‐excess in summer precipitation. Our results suggest that the local cycle of sublimation‐condensation in summer is an important process for the isotopic composition of surface snow, water vapor, and consequently precipitation on inland East Antarctica.

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“…420 000 years at Vostok (Petit et al, 1999), 720 000 years at Dome F (Kawamura et al, 2017) and 800 000 years at Dome C (EPICA, 2004(EPICA, , 2006. Even though reconstructions from ice cores from Greenland and West Antarctica do not extend as far back as from East Antarctica, high resolution analyses of these cores provide very fine temporal resolution from which the seasonal cycle can be resolved (Vinther et al,10 2010; Markle et al, 2017). Seasonal variations are also imprinted in the snow isotopic composition of high accumulation sites in coastal areas of Antarctica (Morgan, 1985;Masson-Delmotte et al, 2003;Küttel et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Archival processes of the water stable isotope signal in East Antarctic ice cores

Casado¹,

Landais²,

Picard³

et al. 2017

Preprint

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Abstract. The oldest ice core records are obtained from the East Antarctic plateau. Water isotopes records are key to reconstructing past climatic conditions over the ice sheet and at the evaporation source. The accuracy of climate reconstructions depends on knowledge of all the processes affecting water vapour, precipitation and snow isotopic compositions. Fractionation processes are well understood and can be integrated in Rayleigh distillation and isotope enabled climate models. However, a quantitative understanding of processes potentially altering the snow isotopic composition after the deposition is still missing. 5In low accumulation sites, such as those found in Antarctica, these poorly constrained processes are likely to play a significant role and limit the interpretation of isotopic composition.Here, we combine observations of isotopic composition in the vapour, the precipitation, the surface snow and the buried snow from Dome C, a deep ice core site on the East Antarctic Plateau. At the seasonal scale, we suggest a significant impact of 10 metamorphism on surface snow isotopic signal compared to the initial precipitation signal. Particularly, in summer, exchanges of water molecules between vapour and snow are driven by the sublimation/condensation cycles at the diurnal scale. Using highly resolved isotopic composition profiles from pits in five Antarctic sites, we identify common patterns, despite different accumulation rates, which cannot be attributed to the seasonal variability of precipitation. Altogether, the difference in the signals observed in the precipitation, surface snow and buried snow isotopic composition constitute evidences of post-deposition 15 processes affecting ice core records in low accumulation areas. 1The Cryosphere Discuss., https://doi

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Global atmospheric teleconnections during Dansgaard–Oeschger events

Cited by 127 publications

References 38 publications

Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores

Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores

Influence of Summer Sublimation on δD, δ¹⁸O, and δ¹⁷O in Precipitation, East Antarctica, and Implications for Climate Reconstruction From Ice Cores

Archival processes of the water stable isotope signal in East Antarctic ice cores

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Global atmospheric teleconnections during Dansgaard–Oeschger events

Cited by 127 publications

References 38 publications

Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores

Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores

Influence of Summer Sublimation on δD, δ18O, and δ17O in Precipitation, East Antarctica, and Implications for Climate Reconstruction From Ice Cores

Archival processes of the water stable isotope signal in East Antarctic ice cores

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Influence of Summer Sublimation on δD, δ¹⁸O, and δ¹⁷O in Precipitation, East Antarctica, and Implications for Climate Reconstruction From Ice Cores