Organization(s):

University of Arizona

What does this program measure?

The program measures accumulated cosmogenic 10Be.

How does this program work?

Approximately 8 sealed plastic carboys filled with purified water are left at MLO for a period of 1-3 years. The carboys will be retrieved at the end of this period, and the concentration of accumulated cosmogenic 10Be will be measured. The carboys are made of thick, UV resistant polyethylene suitable for the extreme conditions at MLO.

Why is this research important?

Information taken from "36Cl production in naturally and artificially irradiated targets (Part of the CRONUS-Earth Initiative), by Marke Zreda and Darin Desilets, University of Arizona)

A major source of uncertainty in applying cosmogenic nuclides to terrestrial surface exposure dating is a lack of knowledge of the spatial dependence of nuclide production rates. Existing scaling models that describe this dependence are all parameterizations of cosmic ray surveys or output from nuclear cascade models. These surveys and modeling results are invaluable, but must ultimately be tested against real measurements of cosmogenic nuclide production in terrestrial materials. The most important variable to constrain is the altitude dependence of production rates, which varies by a factor of ~50 between the tropopause and sea level.

Exposing chemically pure target materials along altitude transects at several geomagnetic latitudes allows meutron fluxes to be measured over the exposrue period at existing neutron monitors to correct for changes in solar modulation. Exposure times of 1-5 years will be required depending on the altitude of the site, the amount of target exposed, and the background fo the process blank.

Are there any trends in the data?

How does this program fit into the big picture?

What is it's role in global climate change?

Mauna Kea, Hawaii is the top candidate for a low latitude transect for several reasons: (a) location within the U.S. will make logistics easier; (b) a range of elevation from sea level to 4000m can be covered; (c) targets can be left at existing astronomy facilities where they will be relatively secure; (d) a neutron monitor is currently operating nearby on Haleakala, Maui; (e) we and others have performed extensive measurements of neutron fluxes in Hawaii; (f) we have already measured cosmogenic nuclide production attenuation length in lava flows on Mauna Kea.

Comments and References