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Radiocarbon dating of ice from a Kilimanjaro plateau glacier

Applicant Schwikowski Margit
Number 144388
Funding scheme Project funding (Div. I-III)
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Climatology. Atmospherical Chemistry, Aeronomy
Start/End 01.01.2013 - 30.09.2014
Approved amount 63'962.00
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All Disciplines (2)

Discipline
Climatology. Atmospherical Chemistry, Aeronomy
Hydrology, Limnology, Glaciology

Keywords (5)

Radiocarbon; Glacier ice; Carbonaceous particles; Dating; Kilimanjaro

Lay Summary (English)

Lead
Lay summary

Lead

Ice samples from the Northern Ice Field of Mount Kilimanjaro will be dated with a new radiocarbon method to resolve the controversy if the near extinction of the ice on Kilimanjaro is unprecedented over the last 11’700 years or has occurred several times throughout the Holocene.

Introduction

High-alpine ice cores from mid- and low-latitude glaciers and ice caps provide regional climate signals in areas inhabited by the majority of the world’s population. Interpreting the information contained in natural climate archives requires a precise chronology. For high-alpine ice cores there is a lack of an appropriate dating tool for the lowermost section since strong ice flow induced layer thinning limits counting of annual layers in the best case to a couple of centuries and is not suitable for the oldest and deepest ice. Glacier flow is dominated by the small-scale geometry of bedrock, resulting in a strongly non-linear depth-age relationship over time, which cannot be fully resolved using physical ice flow models. Under these circumstances, radiocarbon analysis using the insoluble organic carbon aerosol fraction can provide an absolute date.

Aims of the project

This novel radiocarbon approach will be applied on 48 ice samples collected from the Northern Ice Field during our 2011 expedition to Mount Kilimanjaro to help resolving the current debate about the age of the Kilimanjaro plateau glaciers. Palaeoclimate reconstructions based on six ice cores, assigned a basal age of 11’700 years. Another study claims that plateau glaciers on Kilimanjaro are subject to recurring cycles of waxing and waning controlled primarily by atmospheric moisture. An absence of the ice bodies was reconstructed for the period around 850 years ago.

Implications

The Kilimanjaro ice fields are subject to rapid areal shrinkage and thinning. They are expected to disappear within the next few decades. Resolving the controversy if the near extinction of the ice on Kilimanjaro is unprecedented over the last 11’700 years or has occurred several times throughout the Holocene might have wide implications for the understanding of the full range of natural climate variability in the tropics.

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
C-14 MEASUREMENTS OF ICE SAMPLES FROM THE JUVFONNE ICE TUNNEL, JOTUNHEIMEN, SOUTHERN NORWAY-VALIDATION OF A C-14 DATING TECHNIQUE FOR GLACIER ICE
Zapf A., Nesje A., Szidat S., Wacker L., Schwikowski M. (2013), C-14 MEASUREMENTS OF ICE SAMPLES FROM THE JUVFONNE ICE TUNNEL, JOTUNHEIMEN, SOUTHERN NORWAY-VALIDATION OF A C-14 DATING TECHNIQUE FOR GLACIER ICE, in RADIOCARBON, 55(2-3), 571-578.
MICROGRAM-LEVEL RADIOCARBON DETERMINATION OF CARBONACEOUS PARTICLES IN FIRN AND ICE SAMPLES: PRETREATMENT AND OC/EC SEPARATION
Cao Fang, Zhang Yan-Lin, Szidat Soenke, Zapf Alexander, Wacker Lukas, Schwikowski Margit (2013), MICROGRAM-LEVEL RADIOCARBON DETERMINATION OF CARBONACEOUS PARTICLES IN FIRN AND ICE SAMPLES: PRETREATMENT AND OC/EC SEPARATION, in RADIOCARBON, 55(2-3), 383-390.
The onset of Neoglaciation 6000 years ago in western Mongolia revealed by an ice core from the Tsambagarav mountain range
Herren Pierre-Alain, Eichler Anja, Machguth Horst, Papina Tatyana, Tobler Leonhard, Zapf Alexander, Schwikowski Margit (2013), The onset of Neoglaciation 6000 years ago in western Mongolia revealed by an ice core from the Tsambagarav mountain range, in QUATERNARY SCIENCE REVIEWS, 69, 59-68.

Collaboration

Group / person Country
Types of collaboration
Dr. Douglas Hardy, Department of Geosciences, University of Massachusetts United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved


Associated projects

Number Title Start Funding scheme
126515 Radiocarbon dating of glacier ice 01.01.2010 Project funding (Div. I-III)
126515 Radiocarbon dating of glacier ice 01.01.2010 Project funding (Div. I-III)

Abstract

High-alpine ice cores from mid- and low-latitude glaciers and ice caps provide regional climate signals in areas inhabited by the majority of the world’s population. Interpreting the information contained in natural climate archives requires a precise chronology. For high-alpine ice cores there is a lack of an appropriate dating tool for the lowermost section since strong ice flow induced layer thinning limits counting of annual layers in the best case to a couple of centuries and is not suitable for the oldest and deepest ice. Glacier flow is dominated by the small-scale geometry of bedrock, resulting in a strongly non-linear depth-age relationship over time, which cannot be fully resolved using physical ice flow models. Under these circumstances, radiocarbon analysis can provide an absolute date. Radiocarbon dating has been successfully applied to ice cores, when sufficient organic material such as wood fragments or insects was found. However, this has rarely been the case - a fact limiting the wider application of this technique. To overcome this problem, a recently developed approach is to use carbonaceous aerosols contained in the ice for radiocarbon dating. Carbonaceous particles are a major component of naturally occurring aerosols that are emitted ubiquitously or formed in the atmosphere and transported to potential ice core sites. Radiocarbon dating using the organic carbon fraction was applied by our group to different ice cores from Nevado Illimani (Andes, 6’300 m asl), Colle Gnifetti (Alps, 4’450 m asl), and Tsambagarav (Altai, 4’140 m asl). For the first two ice cores the ages cover a time span from 1’000 to more than 10’000 years, whereas the latter has a basal ice age of approximately 6’000 years. This novel radiocarbon approach is promising to help resolving the current debate about the age of the Kilimanjaro plateau glaciers. Palaeoclimate reconstructions based on six ice cores, assigned a basal age of 11’700 years. Another study claims that plateau glaciers on Kilimanjaro are subject to recurring cycles of waxing and waning controlled primarily by atmospheric moisture. An absence of the ice bodies was reconstructed for the period around 850 years ago. This proposal seeks funding for a 1-year extension of the 3-years SNF project “Radiocarbon dating of glacier ice” to finalize the PhD thesis of Alexander Zapf. The aim is the radiocarbon dating of 48 ice samples collected during our 2011 expedition to Kilimanjaro. A stratigraphic sequence of samples from the exposed vertical ice cliffs at the margins of the Northern Ice Field was obtained from horizons characterized by varying particle concentrations. The Kilimanjaro ice fields are subject to rapid areal shrinkage and thinning. They are expected to disappear within the next few decades. Resolving the controversy if the near extinction of the ice on Kilimanjaro is unprecedented over the last 11’700 years or has occurred several times throughout the Holocene might have wide implications for the understanding of the full range of natural climate variability in the tropics.
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