# Vostok, Antarctica Ice Core 4G-2 61-58KYr Methane and d15N Data
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#                World Data Service for Paleoclimatology, Boulder 
#                                  and 
#                     NOAA Paleoclimatology Program 
#             National Centers for Environmental Information (NCEI)
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# Template Version 3.0
# Encoding: UTF-8
# NOTE: Please cite Publication, and Online_Resource and date accessed when using these data. 
# If there is no publication information, please cite Investigators, Title, and Online_Resource and date accessed. 
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# Online_Resource: https://www.ncdc.noaa.gov/paleo/study/23210 
#       Description: NOAA Landing Page
# Online_Resource: https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/vostok2017d15n.txt
#       Description: NOAA location of the template
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# Original_Source_URL:  
#       Description:
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# Description/Documentation lines begin with #
# Data lines have no #
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# Archive: Ice Core
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# Dataset DOI: 
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# Parameter_Keywords: atmospheric gas, nitrogen isotopes 
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# Contribution_Date
#	Date: 2017-12-07
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# File_Last_Modified_Date
#	Date: 2017-12-07
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# Title
#	Study_Name: Vostok, Antarctica Ice Core 4G-2 61-58KYr Methane and d15N Data
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# Investigators
#	Investigators: Fourteau, K.; Faïn X.; Martinerie P.; Landais A.; Ekaykin A.A.; Lipenkov V.Ya.; Chappellaz J.
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# Description_Notes_and_Keywords
#	Description: Vostok, Antarctica 61-58kY 4G-2 ice core d15N of N2.  
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# Publication 
#	Authors: Kévin Fourteau, Xavier Faïn, Patricia Martinerie, Amaëlle Landais, Alexey A. Ekaykin, Vladimir Ya. Lipenkov, and Jérôme Chappellaz
#	Published_Date_or_Year: 2017-12-13     
#	Published_Title: Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions 
#	Journal_Name: Climate of the Past Discussions
#	Volume: 13
#	Edition: 
#	Issue: 12
#	Pages: 1815-1830
#	Report_Number: 
#	DOI: 10.5194/cp-13-1815-2017
#	Online_Resource: https://www.clim-past.net/13/1815/2017/
#	Full_Citation: 
#	Abstract: We investigate for the first time the loss and alteration of past atmospheric information from air trapping mechanisms under low-accumulation conditions through continuous CH4 (and CO) measurements. Methane concentration changes were measured over the Dansgaard-Oeschger event 17 (DO-17, - 60 000 yr BP) in the Antarctic Vostok 4G-2 ice core. Measurements were performed using continuous-flow analysis combined with laser spectroscopy. The results highlight many anomalous layers at the centimeter scale that are unevenly distributed along the ice core. The anomalous methane mixing ratios differ from those in the immediate surrounding layers by up to 50 ppbv. This phenomenon can be theoretically reproduced by a simple layered trapping model, creating very localized gas age scale inversions. We propose a method for cleaning the record of anomalous values that aims at minimizing the bias in the overall signal. Once the layered-trapping-induced anomalies are removed from the record, DO-17 appears to be smoother than its equivalent record from the high-accumulation WAIS Divide ice core. This is expected due to the slower sinking and densification speeds of firn layers at lower accumulation. However, the degree of smoothing appears surprisingly similar between modern and DO-17 conditions at Vostok. This suggests that glacial records of trace gases from low-accumulation sites in the East Antarctic plateau can provide a better time resolution of past atmospheric composition changes than previously expected. We also developed a numerical method to extract the gas age distributions in ice layers after the removal of the anomalous layers based on comparison with a weakly smoothed record. It is particularly adapted for the conditions of the East Antarctic plateau, as it helps to characterize smoothing for a large range of very low-temperature and low-accumulation conditions.
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# Funding_Agency 
#	Funding_Agency_Name: European Community Seventh Framework Programme ERC2011
#	Grant: grant agreement no. 291062 (ERC Ice&Lasers)
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# Funding_Agency 
#	Funding_Agency_Name: INSU/CNRS
#	Grant: LEFE project NEVE-CLIMAT
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# Funding_Agency 
#	Funding_Agency_Name: Laboratoire International Associe Vostok
#	Grant: 
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# Funding_Agency 
#	Funding_Agency_Name: LabEx OSUG@2020
#	Grant: ANR10LABX56
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# Funding_Agency 
#	Funding_Agency_Name: ENS Paris-Saclay
#	Grant: 
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# Site_Information 
#	Site_Name: Vostok
#	Location: Antarctica
#	Country:  
#	Northernmost_Latitude: -78.4661
# 	Southernmost_Latitude: -78.4661
# 	Easternmost_Longitude: -106.8483
# 	Westernmost_Longitude: -106.8483
# 	Elevation: 3500 m
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# Data_Collection   
#	Collection_Name: Vostok2017d15N
#	Earliest_Year: 60829 
#	Most_Recent_Year: 58118
#	Time_Unit: Cal. Year BP
#	Core_Length: 36 m
#	Notes: This dataset is d15N of N2 measured along a section of the 4G-2 Vostok ice core from East Antarctica 895-931m; Earliest and most recent years were given according to the AICC2012 gas age scale;
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# Chronology_Information
#	Chronology: 
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# Variables 
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# Data variables follow are preceded by "##" in columns one and two.
# Data line variables format:  one per line, shortname-tab-variable components (what, material, error, units, seasonality, data type,detail, method, C or N for Character or Numeric data, free text) 
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## depth_m	depth, , , m, , , , ,N,
## d15N	d15N, , ,permil, , Ice cores,,values measured by mass spectrometry in extracted air after water and CO2 trap and corrected for O2/N2 chemical slope, N, 
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# Data:
# Data lines follow (have no #)
# Data line format - tab-delimited text, variable short name as header
# Missing Values: -999
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depth_m	d15N
895	0.46689757
895.5	0.434223392
896	0.422907715
896.5	0.419628326
897	0.454409654
897.5	0.42034719
898	0.449366957
898.6	0.441412646
901.5	0.463233745
902	0.460676969
902.5	0.480007932
903	0.464243023
903.5	0.462577191
904.5	0.480602634
905	0.457068714
905.5	0.45135824
905.98	0.477203738
906.6	0.460946342
907	0.470206528
907.5	0.445906058
908	0.442460413
909	0.435397861
909.48	0.466720594
909.95	0.469489284
911	0.445664511
911.5	0.46008428
912	0.455
912.5	0.464132467
913.5	0.458494096
914.025	0.440777167
914.5	0.489525483
915	0.479981819
915.5	0.452762834
916	0.450198775
916.5	0.454827781
917	0.45093107
917.5	0.463470457
918	0.451000847
918.5	0.443199862
920	0.461429488
921.5	0.454274241
922	0.483041592
922.5	0.482534116
924.26	0.498459193
924.32	0.487101687
924.6	0.466168098
925	0.463508136
926	0.473306383
926.52	0.489401976
927	0.473896683
927.4	0.492276348
928	0.490741461
928.5	0.487655971
930	0.46629736
930.46	0.454394316