Collections allows the user to search in subsets of the existing catalogue. The collections are primarily data management projects that have been incorporated in the ADC catalogue. The collections currently served through ADC include (datasets may belong to multiple data collections):
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A high resolution (0.05 m) water isotopic record (d18O) is available from the NorthGRIP ice core. In this study we look into the water isotope diffusion history as estimated by the spectral characteristics of the d18O time series covering the last 16,000 years. The diffusion of water vapor in the porous medium of the firn pack attenuates the initial isotopic signal, predominantly having an impact on the high frequency components of the power spectrum. Higher temperatures induce higher rates of smoothing and thus the signal can be used as a firn paleothermometer. We use a water isotope diffusion model coupled to a steady-state densification model in order to infer the temperature signal from the site, assuming the accumulation and strain rate history as estimated using the GICC05 layer counted chronology and a Dansgaard-Johnsen ice flow model. The temperature reconstruction accurately captures the timing and magnitude of the Bølling-Allerød and Younger Dryas transitions. A Holocene climatic optimum is seen between 7 and 9 ky b2k with an apparent cooling trend thereafter. Our temperature estimate for the Holocene climatic optimum, points to a necessary adjustment of the ice thinning function indicating that the ice flow model overestimates past accumulation rates by about 10% at 8 ky b2k. This result, is supported by recent gas isotopic fractionation studies proposing a similar reduction for glacial conditions. Finally, the record presents a climatic variability over the Holocene spanning millennial and centennial scales with a profound cooling occurring at approximately 4000 years b2k. The new reconstruction technique is able to provide past temperature estimates by overcoming the issues apparent in the use of the classical d18O slope method. It can at the same time resolve temperature signals at low and high frequencies. ** For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.886044"! ** The overlapping NGRIP I and II core sampled with a 5 cm resolution an measured on an IRMS. Even though the depth is identical, it is not expected that the age is completely identical.
A high resolution (0.05 m) water isotopic record (d18O) is available from the NorthGRIP ice core. In this study we look into the water isotope diffusion history as estimated by the spectral characteristics of the d18O time series covering the last 16,000 years. The diffusion of water vapor in the porous medium of the firn pack attenuates the initial isotopic signal, predominantly having an impact on the high frequency components of the power spectrum. Higher temperatures induce higher rates of smoothing and thus the signal can be used as a firn paleothermometer. We use a water isotope diffusion model coupled to a steady-state densification model in order to infer the temperature signal from the site, assuming the accumulation and strain rate history as estimated using the GICC05 layer counted chronology and a Dansgaard-Johnsen ice flow model. The temperature reconstruction accurately captures the timing and magnitude of the Bølling-Allerød and Younger Dryas transitions. A Holocene climatic optimum is seen between 7 and 9 ky b2k with an apparent cooling trend thereafter. Our temperature estimate for the Holocene climatic optimum, points to a necessary adjustment of the ice thinning function indicating that the ice flow model overestimates past accumulation rates by about 10% at 8 ky b2k. This result, is supported by recent gas isotopic fractionation studies proposing a similar reduction for glacial conditions. Finally, the record presents a climatic variability over the Holocene spanning millennial and centennial scales with a profound cooling occurring at approximately 4000 years b2k. The new reconstruction technique is able to provide past temperature estimates by overcoming the issues apparent in the use of the classical d18O slope method. It can at the same time resolve temperature signals at low and high frequencies. ** For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.886045"! ** The data are measured discretely on an IRMS with a resolution of 2.5 cm. A late Holocene section with an age around 0.9 kab2k.
For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.56098"! ** In this file are hydrogen peroxide and oxygen isotope data from 3 snow pits dug beneath automatic depth gauges at Kento and Summit, and adjacent to a thermocouple string at Summit in 1995. Details of the methodology are found in McConnell et al. (1997).
For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.56091"! ** Data in delta notation, standard is present day atmosphere. Ages are ice ages, calculated by linear interpolation of the Meese et al. (1997) timescale. Not gas ages: no calculation of the ice age-gas age offset in this data set.
For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.60023"! ** Calculated accumulation rates from 14C data (Table 3 in Lal and Jull (1997) compared with glaciological flow-model estimates (Cutler et al., 1995).
For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.56079"! ** Melted water was collected from the outside of samples taken for cation and anion analysis by UNH. An aliquot was taken for anion analysis (chloride, nitrate, sulfate) and the remainder was weakly acidified with HNO3 to yield a final pH of about 2, Be, Cl and Al carriers were added. The Be (and Al and Cl) were concentrated from melted ice using ion exchange resins. Be was eluted from the cation exchange column, precipitated as Be(OH)2 and ignited to BeO for accelerator mass spectrometry (AMS) measurement. AMS measurements at the Lawrence Livermore National Laboratory Center for Accelerator Mass Spectrometry (Davis et al., 1990). The 10Be (half-life =1.5x10^6 years) concentration was normalized to an ICN standard after carrier blank and boron background correction.
For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.55537"! ** Ion data set produced by the Glacier Research Group for the GISP2 D core, from 2 - 3040 m. 2 to 96 m is B core data. The remainder of data is from D core. D core samples were mechanically cleaned between 96-710m and 1370-1510m. All other samples were melted using a teflon coated aluminium apparatus which melted the center portion from a 3.5x3.5cm section of ice.
For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.55532"! ** The timescale includes revisions by D. A. Meese as of Sept 1994. Depths below 167 meters are those of the D core; above 167 meters the depths are those of the B core + 1.09 meters. Layer count ages at top depths where 0 BP represents AD 1950 SUMMER to AD 1949 SUMMER. d18O measured at the Quaternary Isotope Laboratory, Univ of Washington.
For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.56080"! ** Approx age of ice based on layer counting and delta 18O data for trapped air (Grootes et al., 1993; Sowers et al., 1993; Meese et al., 1994a; Stuiver et al., 1995). Typical errors in determination of 14C concentration in recent samples are 50-60 atoms/g, which includes statistical errors and uncertainties. The larger errors arise from multiple extractions, and in samples from depths 100.4 to 1518 from 14C-decay corrections.
For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.56083"! ** Official timescale of GISP2; created by combining the original layer-counted timescale of Meese et al (1994), to about 50,000 years, with a timescale constructed using trace gas measurements from the Vostok and GISP2 cores, placed on the SPECMAP marine timescale. See Bender et al. (1994) for details.
For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.56093"! ** Ice ages were calculated by linear interpolation from the Meese et al. timescale. Depth is midpoint of sample.
For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.60022"! ** Expected in-situ 14C is based on 14C production rate at surface for the present altitude (3.2 km), 200 atoms 14C/g ice/y (Jull et al., 1994), and model ice accumulation rates estimated by Cutler et al. (1995). The estimates are in-situ cosmogenic 14C (i.e. excluding trapped 14C). For total - trapped CO2, the amount of trapped 14CO2 is estimated from the amount of air in the ice (tab1) and assuming 250 ppm CO2 in air.
Paleoatmospheric records of trace-gas concentrations recovered from ice cores provide important sources of information on many biogeochemical cycles involving carbon, nitrogen, and oxygen. Here, we present a 106,000-year record of atmospheric nitrous oxide (N2O) along with corresponding isotopic records spanning the last 30,000 years, which together suggest minimal changes in the ratio of marine to terrestrial N2O production. During the last glacial termination, both marine and oceanic N2O emissions increased by 40 ± 8%. We speculate that our records do not support those hypotheses that invoke enhanced export production to explain low carbon dioxide values during glacial periods. ** For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.205718"!
For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.57226"! ** Measured from meltwater to obtain particle concentration along the shallow portions of the core (<1650 m) before it was replaced by LLS from solid core.
