US International Trans-Antarctic Scientific Expedition (US ITASE) Glaciochemical Data

Sub-annually resolved ice core chemistry data from various sites on the West Antarctic Ice Sheet (WAIS) were obtained from 1999 to 2001 during the US International Trans-Antarctic Scientific Expedition (US ITASE) deployments. Researchers gathered data within the range of 76.0968° S to 90.0000° S and 0.0000° W to 148.7900° W and conducted experiments every 100 km looking for clues representing climatic conditions over the past 200 years. Ice cores, obtained for the glaciochemical component of the US ITASE research, were analyzed for soluble major ion content in order to determine the relationship between depth and the age of the upper ~60 m of firn (older snow pack that has been subjected to compaction and evaporation). At each core/pit site, a 7.6 cm ice core was drilled to a depth between 50 m and 70 m. High-resolution chemical analysis requiring 30 to 50 measurements per meter was used to define each core-chemistry year based on peaks in Na⁺, Ca²⁺, Mg²⁺, K⁺, NH₄⁺, Cl^-, NO₃^-, SO₄^2- (sea salt and non-sea salt), and CH₃SO₃^- (methylsulfonate). Extreme events such as volcanic eruptions provide absolute age horizons within each core that are easily identified in chemical profiles. Such chemical analysis is also useful for quantifying anthropogenic impact and biogeochemical cycling. In addition, snow accumulation rates reported as snow water equivalent (SWE) provided valuable information on ice sheet mass balance, sea level rise, and overall climate variability.

This data set currently contains Na⁺, Cl^-, SO₄^2-, sea salt SO₄^2-(ssSO4), non-sea salt SO₄^2-(nssSO4), and SWE measurements. The remaining ion data will be released as they are published. Core-chemistry tab-delimited text files, an accumulation rate Excel file, an Antarctic location map (GIF format), and a table of information for each core (GIF format) are available via FTP.

Citing These Data

Mayewski, P.A. and D.A. Dixon. 2005. US International Trans-Antarctic Scientific Expedition (US ITASE) glaciochemical data. Boulder, CO, USA: National Snow and Ice Data Center. Digital media.

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Overview Table

Category	Description
Data format	Chemistry data are in tab-delimited text files, and the accumulation data are in an Excel file. An Antarctic location map and a table of information for each core are both in GIF format.
Spatial coverage and resolution	Data were collected on the Western Antarctic Ice Sheet (WAIS) within the range of 76.0968° S to 90.0000° S and 0.0000° W to 148.7900° W. Each core was sampled approximately every 2 cm.
Temporal coverage and resolution	Data were collected from 1999 to 2001 during the Antarctic summer.
Tools for accessing data	The user will need a text editor and spreadsheet software to view the data.
File naming convention	File names correspond to the individual core/pit locations where the data were collected. Please visit Images to view a map of the core/pit locations.
File size	Files sizes range from 29 KB to 321 KB. The entire data set is approximately 2.3 MB.
Parameter(s)	Concentrations of the ions Na⁺, Cl^-, and SO₄^2- (sea salt and non-sea salt) were reported along with the snow water equivalent (SWE). The remaining data for Ca²⁺, Mg²⁺, K⁺, NH₄⁺, NO₃^-, and CH₃SO₃^- (methylsulfonate) will be released as they become published.
Procedures for obtaining data	Data are available via FTP.

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments

Investigators

Paul A Mayewski
Climate Change Institute
Global Science Center, University of Maine
Orono, ME, USA

Daniel A Dixon
Climate Change Institute
Global Science Center, University of Maine
Orono, ME, USA

Technical Contact

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

Acknowledgements

This grant was supported by the National Science Foundation (NSF) Office of Polar Programs (OPP) award OPP-9725057.

2. Detailed Data Description

Format

Chemistry data are in tab-delimited text files, and the accumulation data are in an Excel file. An Antarctic location map and a table of information for each core are in GIF format.

File Naming Convention

File names correspond to the year each core was extracted, along with individual core/pit locations where the data were collected. Data from cores obtained in the Central West Antarctic are preceded with "CWA". Data from cores obtained in the Ross Ice Drainage System obtained in 1995 are preceded with "RIDS". The Up-C core location refers to the Ice Stream C recently named the Kamb Ice Stream. The "SP95_Chem.txt" file contains data from the South Pole core recovered in 1995. The "SDM1994.txt" file contains data from the Siple Dome core recovered in 1994. The data from cores that were extracted prior to the US ITASE deployment in 1999 are included in this data set for comparison purposes. Please visit Images to view a map of the core/pit locations along with a table of information about each core.

File Size

Files sizes range from 29 KB to 321 KB. The entire data set is approximately 2.3 MB.

Spatial Coverage

Southernmost Latitude: 90.0000° S
Northernmost Latitude: 76.0968° S
Westernmost Longitude: 148.7900° W
Easternmost Longitude: 0.0000° W

Spatial Coverage Map

The map above shows the traverse routes of the U.S. portion of the International Trans-Antarctic Scientific Expedition (US ITASE).

Temporal Coverage

These US ITASE data were collected during the Antarctic summer from 1999 to 2001. These data were used for reconstruction of sub-annual scale climate variability and changes in the chemistry of the atmosphere over the last 200+ years.

Parameter or Variable

Parameter Description

The researchers analyzed a glaciochemical series of ion concentrations including Na⁺, Ca²⁺, Mg²⁺, K⁺, NH₄⁺, Cl^-, NO₃^- SO₄^2-, and CH₃SO₃^- (methylsulfonate). They studied annual accumulation rates by using snow water equivalents (SWE). They reported concentrations of the ions Na⁺, Cl^-, and SO₄^2- (sea salt and non-sea salt). The remaining data for Ca²⁺, Mg²⁺, K⁺, NH₄⁺, NO₃^-, and CH₃SO₃^- (methylsulfonate) will be released as they are published. The ionic composition of polar ice cores provides a stratigraphic tool for relative dating that can be extremely effective on the Western Antarctic Ice Sheet (WAIS). It also allows researchers to document changes in chemical species source emissions and to characterize the major atmospheric circulation systems affecting WAIS.

Unit of Measurement

Ion concentrations are reported in micrograms per liter (µg/L). SWE is reported in centimeters (cm).

Sample Data Record

3. Data Access and Tools

Data Access

Volume

Software and Tools

The user will need a text editor and spreadsheet software in order to view the data.

Related Data Collections

4. Data Acquisition and Processing

Sensor or Instrument Description

Data are generated using a new Sneed-Handley continuous melter system and an ion chromatograph (IC) instrument. The data consist of dissolved major ion concentrations at sub-annual resolution for the length of each core. The ions Na (sodium), NH4 (ammonium), K (potassium), Mg (magnesium), Ca (calcium), Cl (chloride), NO3 (nitrate), SO4 (sulfate), and MS (methylsulfonate) either individually or in combinations, indicate many different processes occurring in, around, or over Antarctica. By looking at these ion concentrations down ice cores, researchers can obtain accurately dated, sub-annual records of Antarctic meteorological and glaciochemical processes hundreds, or sometimes thousands of years into the past.

The University of Maine's continuous melter (UMCoM) system is housed in a dedicated clean room with HEPA filtered air. Standard clean room procedures are employed during melting. A Wagenbach-style continuous melter system was modified to include a pure Nickel melthead that can be easily dismantled for thorough cleaning. The system allows ice and firn to melt without wicking the meltwater into unmelted core. Unlike ice core melter systems in which the meltwater is directly channeled to online instruments for continuous flow analyses, the UMCoM system collects discrete samples for each chemical analysis under clean conditions.

Data Acquisition Methods

The US ITASE field season involved drilling numerous ice cores and collecting snow pit samples along several traverse segments (see map for core locations). At each core/pit site, a 7.6 cm ice core was drilled to a depth between 50 m and 70 m. Workers wearing non-particulating suits, polyethylene gloves, and particle masks sampled snow pits and processed ice cores. Samples were stored in precleaned polyethylene containers and stored below -15° C until melting immediately prior to chemical analysis. Major ions were analyzed using ion chromatography. High-resolution chemical analysis requiring 30 to 50 measurements per meter was used to define each core-chemistry year based on peaks in Na⁺, Ca²⁺, Mg²⁺, K⁺, NH₄⁺, Cl^-, NO₃^-, SO₄^2- (sea salt and non-sea salt), and CH₃SO₃^- (methylsulfonate).

5. References and Related Publications

Dixon, D., P.A. Mayewski, S.D. Kaspari, K.J. Kreutz, G.S. Hamilton, K. Maasch, S.B. Sneed, M.J. Handley. 2005. A 200-year sulfate record from sixteen Antarctic ice cores and associations with Southern Ocean sea ice extent. Annals of Glaciology 41, in press.

Dixon, D., P.A. Mayewski, S. Kaspari, S. Sneed and M. Handley. 2004. A 200 year sub-annual record of sulfate in West Antarctica from 16 ice cores. Annals of Glaciology 39: 545-556.

Kaspari, S.D., P.A. Mayewski, D.A. Dixon, S.B. Sneed, M.J. Handley. 2005. Sources and transport pathways of marine aerosol species into West Antarctica. Annals of Glaciology 41, in press.

Kaspari, S., P.A. Mayewski, D. Dixon, V.B. Spikes, S. Sneed, M. Handley and G.S. Hamilton. 2004. Climate variability in West Antarctica derived from annual accumulation-rate records from ITASE firn/ice cores. Annals of Glaciology 39: 585-594.

Mayewski, P.A. 2003. Antarctic oversnow traverse-based Southern Hemisphere climate reconstruction. Eos 84(22): 205 and 210.

6. Document Information

List of Acronyms

CWA: Central West Antarctic
FTP: File Transfer Protocol
ITASE: International Trans-Antarctic Scientific Expedition
NSIDC: National Snow and Ice Data Center
RIDS: Ross Ice Drainage System
SWE: Snow water equivalent
WAIS: Western Antarctic Ice Sheet

Depth (m)	YEAR (AD)	Na	Cl	SO4	nssSO4	ssSO4
0	2001	23.31	48.48	51.63	47.57146	4.058537
0.02	2000.962963	11.13	28.78	24.27	23.22935	1.04065
0.04	2000.925926	1.78	13.93	16.08	16.05919	0.020813
0.06	2000.888889	13.88	26.97	19.55	18.46772	1.082276
0.08	2000.851852	19.01	40.85	19.52	16.77268	2.747317
0.1	2000.814815	20.5	41.37	20.93	17.84968	3.080325
0.12	2000.777778	25.15	40.94	19.18	15.55854	3.621463
0.14	2000.740741	58.98	58.97	25.35	18.68984	6.660163
0.16	2000.703704	199.83	330.43	49.28	27.21746	22.06255
0.18	2000.666667	217.15	379.04	50.2	20.45746	29.74255
0.2	2000.62963	196.14	312.29	41.4	13.752	27.648