Additional Participants

Graduate Student

Kevin Carpenter
Daniel Voisin

Technician, Programmer

Sharon Sneed
Sallie Whitlow

Organizational Partners

New Mexico Tech

Project Period

September 1, 2000-May 31, 2002

Level of Access

Open-Access Report

Grant Number

0049041

Submission Date

9-9-2002

Abstract

This project was a pilot project to determine if the ice on Mt. Moulton provides a reliable record of past climatic conditions. The area of study is a several hundred-meter section of blue ice (Trench A) that spans the time period from approximately the early Holocene to over 492k years ago. Dating control is obtained through radiometrically-dated tephra layers (i.e., air fall deposits) within the section (Figure 1) originating from the adjacent Mt. Berlin. Fieldwork during the 1999-2000 field season included the trenching of the complete section with electric chain saws mounted on a wheeled frame. Blocks were extracted and cut-down to sample a continuous section from the 50-cm depth. Several overlapping trenches, some completed to a depth of 1 meter, were sampled to test the validity of sampling at the 50-cm depth. Individuals from New Mexico Tech, collaborators in the project, developed a detailed map of visible tephra layers using a GPS and collected additional tephra samples with the goal of dating layers not presently dated and for refining existing ages. Once samples were brought back to the lab, a glaciochemistry time series was developed for comparison with other such records from Antarctica as well as from Greenland ice cores. Through the use of an ion chromatograph, concentrations of the major ions found in the atmosphere are determined. The suite of chemical species measured includes Na2+, Ca2+, Mg2+, K+, NH4+, Cl-, SO42-, and NO3-. One sample per 20 cm of ice was analyzed over the last ~150k to obtain a coarsely-resolved record to test the reliability of the record. Figure 1 shows the relationship between the Na2+ time series and the location of the dated tephra layers, thus the age model developed for Trench A. A similarity in broad trends would suggest that Mt. Moulton ice contains a valid paleoclimatic record thereby warranting more detailed (i.e., a much higher resolution) sampling and analyses than done in this study. As this was a pilot project the only presentations made were at meetings of the U.S. Ice Core Working Group and at meetings for the Siple Dome ice-coring project.

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