# WAIS Divide Ice Core 2400 Year Sulfate and Nitrate Isotope Data
#----------------------------------------------------------------------- 
#                World Data Center for Paleoclimatology, Boulder 
#                                  and 
#                     NOAA Paleoclimatology Program 
#----------------------------------------------------------------------- 
# NOTE: Please cite original reference when using these data,
# plus the Online Resource and date accessed.
#
# Online_Resource: http://www.ncdc.noaa.gov/paleo/study/14172
#
# Original_Source_URL: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/wais2013d15n.txt
# 
# Description/Documentation lines begin with #
# Data lines have no #
#
# Archive: Ice Cores
#--------------------
# Contribution_Date
#	Date: 2013-03-28    
#	Updated: 2014-10-07
#--------------------
# Title
#	Study_Name: WAIS Divide Ice Core 2400 Year Sulfate and Nitrate Isotope Data
#--------------------
# Investigators
#       Investigators: Sofen, E.D.; Alexander, B.; Steig, E.J.; Thiemens, M.H.; Kunasek, S.A.; Amos, H.M.; Schauer, A.J.; Hastings, M.G.; Bautista, J.; Jackson, T.L.; Vogel, L.E.; McConnell, J.R.; Pasteris, D.R.; Saltzman, E.S.  
#--------------------
# Description_and_Notes
#	Description: Isotopic composition of sulfate and nitrate from 3 WAIS Divide Ice Cores.  Data set updated 10/7/2014 to add age model, correct citation,
#	and add additional data (accumulation, MSA, NO3-, H2O2, Sulfur, Acid, NA+, water d18O).
#--------------------
# Publication 
#       Authors: Sofen, E.D., B. Alexander, E.J. Steig, M.H. Thiemens, S.A. Kunasek, H.M. Amos, A.J. Schauer, M.G. Hastings, J. Bautista, T.L. Jackson, L.E. Vogel, J.R. McConnell, D.R. Pasteris, and E.S. Saltzman 
#       Published_Date_or_Year: 2014-06-11     
#       Published_Title: WAIS Divide ice core record suggests sustained changes in the chemical formation pathways of sulfate and nitrate aerosol since the 19th century
#       Journal_Name: Atmospheric Chemistry and Physics
#       Volume: 14
#       Edition: 
#       Issue: 11
#       Pages: 5749-5769
#       DOI: 10.5194/acp-14-5749-2014
#       Online_Resource: http://www.atmos-chem-phys.net/14/5749/2014/acp-14-5749-2014.html
#       Abstract: The 17O excess (D17O = d17O-0.52 x d18O) of sulfate and nitrate reflects the relative importance of their different production pathways in the atmosphere. A new record of sulfate and nitrate D17O spanning the last 2400 years from the West Antarctic Ice Sheet Divide ice core project shows significant changes in both sulfate and nitrate D17O in the most recent 200 years, indicating changes in their formation pathways. The sulfate D17O record exhibits a 1.1 per mil increase in the early 19th century from (2.4 +/- 0.2) per mil to (3.5 +/- 0.2) per mil, which suggests that an additional 12-18% of sulfate formation occurs via aqueous-phase production by O3, relative to that in the gas phase. Nitrate D17O gradually decreases over the whole record, with a more rapid decrease between the mid-19th century and the present day of 5.6 per mil, indicating an increasing importance of RO2 in NOx cycling between the mid-19th century and the present day in the mid- to high-latitude Southern Hemisphere. The former has implications for the climate impacts of sulfate aerosol, while the latter has implications for the tropospheric O3 production rate in remote low-NOx environments. Using other ice core observations, we rule out drivers for these changes other than variability in extratropical oxidant (OH, O3, RO2, H2O2, and reactive halogens) concentrations. However, assuming OH, H2O2, and O3 are the main oxidants contributing to sulfate formation, Monte Carlo box model simulations require a large (>= 260%) increase in the O3 /OH mole fraction ratio over the Southern Ocean in the early 19th century to match the sulfate D17O record. This unlikely scenario points to a~deficiency in our understanding of sulfur chemistry and suggests other oxidants may play an important role in sulfate formation in the mid- to high-latitude marine boundary layer. The observed decrease in nitrate D17O since the mid-19th century is most likely due to an increased importance of RO2 over O3 in NOx cycling and can be explained by a 60-90% decrease in the O3 / RO2 mole fraction ratio in the extratropical Southern Hemisphere NOx-source regions.
#------------------
# Funding_Agency 
#       Funding_Agency_Name: US National Science Foundation
#       Grant: ANT-0538049, AGS-0704169
#------------------
# Site_Information 
#       Site_Name: WDC-05A
#       Location: Antarctica
#	Region: 
#	Country: 
#	Northernmost_Latitude: -79.4676 
# 	Southernmost_Latitude: -79.4676
# 	Easternmost_Longitude: -112.1251
# 	Westernmost_Longitude: -112.1251
# 	Elevation: 1806 m  
#------------------
# Data_Collection   
#	Collection_Name: WDC05Ad15N
#	Earliest_Year: 1775
#	Most_Recent_Year: 2008
#	Time_Unit: AD
#	Core_Length: 68.815 m
#	Notes: 
#------------------
# Chronology: 
#
# 
# 	
#----------------	
# Variables 
#
# Data variables follow (have no #)
# Data line variables format:  Variables list, one per line, shortname-tab-longname-tab-longname components (9 components: what, material, error, units, seasonality, archive, detail, method, C or N for Character or Numeric data) 
# WDC05A Nitrate d15N st. dev. per mil based on duplicate/triplicate measurements of samples
#
##depth_top_m	Depth top of sample interval, , , m, , ,top of sample, ,N
##depth_bot_m	Depth bottom of sample interval, , , m, , ,bottom of sample, ,N
##d15NNO3	delta 15N Nitrate, , , per mil, , , , ,N
##d15NNO3std	delta 15N Nitrate standard deviation, , , per mil, , , , ,N
#
#----------------
# Data:
# Data lines follow (have no #)
# Data line format - tab-delimited text, variable short name as header
# Missing Values:  
		
depth_top_m	depth_bot_m	d15NNO3	d15NNO3std
0	0.99	11.21	0.55
0.99	1.95	10.73	0.55
1.95	2.94	10.83	0.55
2.94	3.935	15.68	0.55
3.935	4.865	4.38	0.55
4.865	5.92	7.01	0.55
5.92	6.915	1.65	0.55
6.915	7.91	9.23	0.55
7.91	8.905	7.96	0.55
8.905	9.9	9.27	0.55
9.9	11	4.97	0.55
11	11.895	2.49	0.55
11.895	12.93	7.17	0.55
12.93	13.885	13.6	0.55
13.885	14.885	3.73	0.55
14.885	15.88	12.66	0.55
15.88	17	5.68	0.55
17	17.875	15.69	0.55
17.875	18.875	13.08	0.55
18.875	19.87	5.75	0.55
19.87	20.865	6.06	0.55
20.865	21.86	4.48	0.55
21.86	22.855	8.65	0.55
22.855	23.83	4.26	0.55
23.83	24.855	5.13	0.55
24.855	25.85	7	0.55
25.85	26.845	6.86	0.55
26.845	27.84	8.77	0.55
27.84	28.835	6.45	0.55
28.835	29.805	6.06	0.55
29.805	30.83	7.71	0.55
30.83	31.83	6.13	0.55
31.83	32.82	6.76	0.55
32.82	33.82	8.83	0.55
33.82	34.82	4.51	0.55
34.82	35.815	5.64	0.55
35.815	36.815	2.55	0.55
36.815	37.84	5.14	0.55
37.84	38.81	6.19	0.55
38.81	39.805	7.06	0.55
39.805	40.795	2.81	0.55
40.795	41.795	11.21	0.55
41.795	42.79	9.21	0.55
42.79	43.79	3.37	0.55
43.79	44.785	7.23	0.55
44.785	45.785	10.67	0.55
45.785	46.78	6.27	0.55
46.78	47.775	14.47	0.55
47.775	48.77	3.53	0.55
48.77	49.775	6.57	0.55
49.775	50.775	5.4	0.55
50.775	51.77	12.2	0.55
51.77	52.77	4.77	0.55
52.77	53.8	4.44	0.55
53.8	54.795	5.69	0.55
54.795	55.79	6.66	0.55
55.79	56.84	4.91	0.55
56.84	57.835	6.94	0.55
57.835	58.77	7.12	0.55
58.77	59.77	9.9	0.55
59.77	60.81	10.65	0.55
60.81	61.76	7.57	0.55
61.76	62.745	10.34	0.55
62.745	63.745	12.11	0.55
63.745	64.74	7.19	0.55
64.74	65.735	2.95	0.55
65.735	66.79	1	0.55
66.79	67.83	4.86	0.55
67.83	68.815	6.97	0.55
68.815	69.8	3.57	0.55