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Tracking glacial erosion and glacier occupation in the Alps with the unique combination of measurement and modeling of 10Be, 14C, and 36Cl in bedrock

English title Tracking glacial erosion and glacier occupation in the Alps with the unique combination of measurement and modeling of 10Be, 14C, and 36Cl in bedrock
Applicant Ivy-Ochs Susan
Number 135448
Funding scheme Project funding (Div. I-III)
Research institution Labor für Ionenstrahlphysik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geology
Start/End 01.09.2011 - 30.09.2014
Approved amount 195'982.00
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Keywords (8)

Alps; glacial erosion; cosmogenic nuclides; 10Be 14C 36Cl; Last Glacial Maximum; Lateglacial; Holocene;

Lay Summary (English)

Lead
Lay summary
The distinctive and unique character of the Alps; from the deep U-shaped valleys to the jagged ridges above the cirques document the work of glaciers over hundreds of millenia. Repeated glaciation plays as well a key role in generation of relief and sets limits to overall topography in the Alps. Never-the-less, relatively little is known about the rates and patterns in space and time of how subglacial erosion works. Quite fundamental questions such as: How long did it take for glaciers to carve the deep troughs and overdeepenings?, How did the trough shoulder itself form?, and How does the shape of cirques evolve? remain unanswered. In this project we combine detailed understanding of the morphologic setting in the chosen study sites based on field mapping and DEM analyses with cosmogenic nuclide determinations and modeling. Cosmogenic nuclides are made in the upper decimeters of rock that is exposed to cosmic rays. Removal of rock due to erosion by glaciers will remove nuclides that were produced before the glaciation. But depending on how deeply the glacier erodes not all nuclides will be removed. Because different nuclides (10Be, 14C, and 36Cl) have different production depth patterns we can combine them to quantify the depth of glacial erosion by sampling granite/granodiorite at select spots in a valley or cirque transect. The inclusion of in-situ produced 14C in quartz is key. Because 14C decays more rapidly than the other two nuclides, it can be used to constrain if and for how long a site was covered by ice during the last 15,000 years. A key component of the proposed study is the modelling of periods of exposure, coverage and depth of glacial erosion into the bedrock based on the obtained radionuclide data. We begin work this summer at first sites (in the regions of Haslital Switzerland and Zillertal Austria), additional sites will be carefully evaluated based on field investigations and DEM analyses. As the sites lie in the realms of Last Glacial Maximum (ca. 25,000 years ago), Lateglacial (between 18,000 and 11,000 years ago) and Holocene paleoglaciers we will not only shed light on how fast and where in the landscape glaciers erode but will provide additional pieces to the puzzle of the timing of climate variations during the last 25,000 years.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
A deglaciation model of the Oberhasli, Switzerland
Wirsig Christian, Zasadni Jerzy, Ivy‐Ochs Susan, Christl Marcus, Kober Florian, Schlüchter Christian (2016), A deglaciation model of the Oberhasli, Switzerland, in Journal of Quaternary Science, 31(1), 46-59.
Combined cosmogenic 10Be, in situ 14C and 36Cl concentrations constrain Holocene history and erosion depth of Grueben glacier (CH)
Wirsig Christian, Susan Ivy-Ochs, Akçar Naki, Lupker Maarten, Hippe Kristina, Wacker Lukas, Vockenhuber Christof, Schlüchter Christian (2016), Combined cosmogenic 10Be, in situ 14C and 36Cl concentrations constrain Holocene history and erosion depth of Grueben glacier (CH), in Swiss Journal of Geosciences, 109(3), 379-388.
Dating the onset of LGM ice surface lowering in the High Alps
Wirsig Christian, Zasadni Jerzy, Christl Marcus, Akçar Naki, Ivy-Ochs Susan (2016), Dating the onset of LGM ice surface lowering in the High Alps, in Quaternary Science Reviews, 143, 37-50.
Subglacial abrasion rates at Goldbergkees, Hohe Tauern, Austria, determined from cosmogenic 10Be and 36Cl concentrations
Wirsig Christian, Susan Ivy‐Ochs Susan, Reitner Jürgen, Christl Marcus, Vockenhuber Christof, Bichler Mathias, Reindl Martin, Subglacial abrasion rates at Goldbergkees, Hohe Tauern, Austria, determined from cosmogenic 10Be and 36Cl concentrations, in Earth Surface Processes and Landforms .

Collaboration

Group / person Country
Types of collaboration
Université de Savoie France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Geological Survey Austria Austria (Europe)
- in-depth/constructive exchanges on approaches, methods or results
AGH University of Science and Technology Krakow Poland (Europe)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Nordic workshop on Cosmogenic Nuclide Dating 2014 Poster Refining the deglaciation chronology in the High Alps based on cosmogenic Be-10 11.06.2016 aarhus, Denmark Ivy-Ochs Susan; Wirsig Christian;
Nordic workshop on Cosmogenic Nuclide Dating 2014 Talk given at a conference Using cosmogenic 10Be and 36Cl to assess the depth of glacial erosion in the Alps 11.06.2016 Aarhus, Denmark Wirsig Christian; Ivy-Ochs Susan;
DPG Frühjahrstagung 2015 Talk given at a conference Erkenntnisse über die Geschichte eines Alpengletschers durch Kombination von kosmogenem Be-10, in-situ C-14 und Cl-36 25.03.2016 Heidelberg, Germany Wirsig Christian;
13th International Conference on Accelerator Mass Spectrometry (AMS-13) 2014 Talk given at a conference Combined cosmogenic Be-10 and Cl-36 nuclide concentrations constrain subglacial erosion rates 28.07.2014 Aixe en Provence, France Alfimov Vasily; Wirsig Christian;
EGU 2014 Poster Constraining local subglacial bedrock erosion rates with cosmogenic nuclides 27.04.2014 Vienna, Austria Wirsig Christian; Ivy-Ochs Susan;
DPG Frühjahrstagung 2014 Talk given at a conference Quantifizierung glazialer Erosion mit kosmogenen Nukliden 28.03.2014 Dresden, Germany Wirsig Christian;
8th International Conference on Geomorphology 2013 Talk given at a conference Timing of ice decay after the LGM in the high Alps 27.08.2013 Paris, France Schlüchter Christian; Wirsig Christian; Ivy-Ochs Susan; Alfimov Vasily;
DPG-Frühjahrstagung der Sektion AMOP 2013 Poster Datierung des Zerfalls der Eismasse des letzteiszeitlichen Maximums in den Alpen mit kosmogenem 10Be 18.03.2013 Hannover, Germany Ivy-Ochs Susan; Schlüchter Christian; Alfimov Vasily; Wirsig Christian;
Radiocarbon 2012 Poster A comparison of exposure-dated and radiocarbon-dated Sites in the Alps: What can we learn? 09.07.2012 Paris, France Ivy-Ochs Susan; Schlüchter Christian;
EGU 2012 Poster Combining cosmogenic Be, C, Al and Cl ‐ Quantifying depth of glacial erosion and timing of deglaciation 22.04.2012 Vienna, Austria Alfimov Vasily; Schlüchter Christian; Ivy-Ochs Susan; Wirsig Christian;


Knowledge transfer events



Self-organised

Title Date Place
Oral presentation and tour for gymnasium students Wettingen 19.11.2014 Zurich, Switzerland
Oral presentation and tour for gymnasium students Rämibühl 05.02.2014 Zurich, Switzerland
Oral presentation and tour for gymnasium students Wettingen 26.06.2013 Zurich, Switzerland
Oral presentation and tour for gymnasium students Wettingen 07.11.2012 Zurich, Switzerland
Oral presentation and tour for gymnasium students Rämibühl 08.02.2012 Zurich, Switzerland
Oral presentation and tour for gymnasium students Rämibühl 06.02.2012 Zurich, Switzerland

Awards

Title Year
Silver Medal of ETH Zurich for outstanding Doctoral Thesis from Department of Earth Sciences 2016

Associated projects

Number Title Start Funding scheme
156187 Reconstructing patterns of bedrock glacial erosion and Lateglacial glacier extents in the Alps with field mapping and cosmogenic 10Be, 14C, and 36Cl analyses 01.10.2014 Project funding (Div. I-III)

Abstract

Glaciers have shaped the Alps. The landforms we see, such as U-shaped glacial troughs, trough shoulders and cirques, the marked relief, as well as the overall elevation of the Alps can all be attributed to the action of glaciers. Never-the-less, relatively little is known about the rates and patterns in space and time of how the process of subglacial erosion works. Quite fundamental questions such as: How long did it take for glaciers to carve the deep troughs and overdeepenings?, How did the trough shoulder itself form?, How do cirques evolve? remain unanswered. The goal of this proposal is to quantify the fundamental process of subglacial erosion. We propose to combine detailed understanding of the morphologic setting in the chosen study sites based on field mapping and DEM analyses with cosmogenic nuclide determinations and modeling. We specifically choose the unique combination of 10Be, 14C, and 36Cl in bedrock because of their different characteristics; markedly different half-lives (14C t½=5730 years, 36Cl t½=300,000 years, 10Be t½=1,390,000 years) and distinctly different production depth profiles. Production of 36Cl does not drop off as rapidly with depth in rock as does 10Be and 14C thus 36Cl can be used more effectively than the other two to quantify how much rock has been removed during glaciations. 14C decays much more rapidly than the other two nuclides, therefore it can be used to constrain how long a site has been covered by ice over the last 15-20 kyr. The inclusion of in-situ produced 14C in such studies is critical and very few research groups have this capability. For this investigation, we have chosen two study areas in the Alps, specifically Grimsel/Haslital region (Switzerland) and Zillertal (Austria) in which we will focus on the following basic questions in Alpine Quaternary geology and geomorphology:1) Was post-LGM (Last Glacial Maximum) ice surface lowering in the high Alps simultaneous with foreland deglaciation? We will exposure date truncated bedrock spurs and high-elevation erratics in Haslital and Zillertal with 10Be and 36Cl to address this question. 2) Was glacial erosion on the sides of the trough dominated by abrasion? The valley walls may have been formed during repeated pre-LGM glaciations and were only polished during the LGM. This will be tested by looking for inherited 36Cl and 10Be (nuclides acquired before the LGM) in the polished bedrock walls of Haslital and Zillertal. 3) What is the origin of the trough shoulder and the trough kante (edge of the trough)? Are they relict features? In that case 10Be and 36Cl concentrations in bedrock from the trough shoulder would contain inheritance. We plan to compare these landforms in the two study regions.4) Do cirques really evolve more through headwall retreat than from downwearing of the bed? If this is true bedrock on the outermost margin of a cirque may still contain nuclides, 10Be and especially 36Cl, acquired during the Lateglacial prior to Holocene readvances. Nuclide concentrations should decrease going in an up-glacier direction. In this regard 14C is crucial as it will show us the length of time that the cirque glacier was expanded (and the site was covered) during the Holocene. We have already chosen first sites, additional sites will be carefully evaluated based on field investigations and DEM analyses. A key component of the proposed study is the modelling of periods of exposure, coverage and depth of glacial erosion into the bedrock based on the obtained radionuclide data. The proposal investigators and collaborators have decades of experience in the interpretation of glacial landscapes in the Alps and application of cosmogenic nuclides in glacial geomorphological studies. The nuclide modeling will therefore be strictly constrained by plausible scenarios for periods of glacier expansion based on the known field record. We are uniquely positioned in the international community to use the three cosmogenic nuclides, 10Be, 14C and 36Cl, to study glacial erosion and the timing of glacial occupation.
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