Differing Chemical Weathering Conditions in Meltwater Catchments of

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Differing Chemical Weathering Conditions in Meltwater Catchments of Western Greenland (C 54 A-06) K.

Differing Chemical Weathering Conditions in Meltwater Catchments of Western Greenland (C 54 A-06) K. Deuerling, J. Martin University of Florida, Department of Geological Sciences J. Gulley University of Texas Institute for Geophysics American Geophysical Union, Fluxes of Water and Methane Associated With Changing Permafrost: Earth and Beyond III, 09 December 2011

Glacial Foreland Stream Morphology Proglacial Streams • • ↑ discharge ↑ suspended sediment load

Glacial Foreland Stream Morphology Proglacial Streams • • ↑ discharge ↑ suspended sediment load ↓ vegetation mixed water source Deglaciated Streams • • ↓ discharge ↓ suspended sediment load ↑ vegetation precipitation water source

Current Greenland Permafrost Conditions • Continuous permafrost (tan) roughly following the -5°C mean annual

Current Greenland Permafrost Conditions • Continuous permafrost (tan) roughly following the -5°C mean annual temperature isotherm (Funder, 1989) • Discontinuous permafrost (yellow) • Isolated permafrost (red-orange) Local permafrost-draining stream (left) and lake (above), Paakitsoq, West Greenland. Nielsen (2010)/GEUS

Question How do weathering processes differ between the deglaciated and proglacial environments? Significance •

Question How do weathering processes differ between the deglaciated and proglacial environments? Significance • Elucidate effects of morphology, vegetation on weathering conditions in glacial foreland • Ground-truth how current weathering conditions are exported to marine records (sediments and dissolved load)

Field Site ETM+ Landsat Imagery • ~40 km northeast of Ilulissat (Jakobshavn) • Primarily

Field Site ETM+ Landsat Imagery • ~40 km northeast of Ilulissat (Jakobshavn) • Primarily tonalitic granodiorite bedrock (van Gool et al. , 2002) Google Earth • 4 streams sampled: 2 turbid proglacial (PG; red) 2 clear deglaciated (DG; blue)

Water Source • Separation indicates different water sources • Local precipitation (DG) and ice

Water Source • Separation indicates different water sources • Local precipitation (DG) and ice melt (PG)

Specific Conductivity • DG: downstream increase due to low water-rock ratio, longer retention time

Specific Conductivity • DG: downstream increase due to low water-rock ratio, longer retention time • PG: downstream decrease due to dilution

Specific Conductivity • DG: no trend between total suspended solids (TSS) and Sp. C

Specific Conductivity • DG: no trend between total suspended solids (TSS) and Sp. C • PG: direct relationship between TSS and Sp. C

Major Elements • Tonalitic granodiorite • • Plagioclase (Ca, Na) K-feldspar (K) Biotite (K,

Major Elements • Tonalitic granodiorite • • Plagioclase (Ca, Na) K-feldspar (K) Biotite (K, Fe, Mg) Amphiboles/pyroxenes (Ca, Fe, Mg) • DG streams: evolution of snowmelt, increased weathering of feldspars (Ca, Na) • PG streams: downstream dilution • ↑ Mg – weathering of mafic minerals

Summary • DG & PG streams have different water chemistries and potential weathering environments

Summary • DG & PG streams have different water chemistries and potential weathering environments • DG streams – feldspar weathering, long retention times, low water: rock • Enriched δD and δ 18 O • High Ca, Na+K values • Low Mg, Fe values • PG streams – mafic weathering in suspended sediments • Depleted δD and δ 18 O • Low intial Ca values • High initial Mg, K, Fe values Implications • As glaciers recede, deglaciated catchments become more important • Bulk chemical weathering signal changes • Solute/isotope fluxes to marine system change

Future Work • Mineralogical analyses of unweathered bedrock/regolith, bedload sediments, and suspended sediments (optical,

Future Work • Mineralogical analyses of unweathered bedrock/regolith, bedload sediments, and suspended sediments (optical, XRD) • Understand what is available to weather (bedrock/regolith) • Look for direct evidence for incongruent weathering & aluminosilicate formation (bedload/suspended load) • Calculate solute/isotope fluxes from each catchment type • Radiogenic isotopes of water, sediment, and rock samples • Discern degree of weathering, isotopic fluxes from each weathering environment • Investigate relationship of landscape age and flux • Expand further south

References • • • Craig (1961) Science 133: 1702 -1703. Funder (1989) Quaternary Geology

References • • • Craig (1961) Science 133: 1702 -1703. Funder (1989) Quaternary Geology of Canada and Greenland K-1, 741 -792. van Gool et al. (2002) Geology of Greenland Survey Bulletin 191, 13 -23. Henriksen et al. (2000) Geology of Greenland Survey Bulletin 185: 1 -98. Mernild et al. (2010) The Cryosphere 4: 231 -242. Nielsen (2010) Present Conditions in Greenland the Kangerlussuaq Area. GEUS Working Report. Schwartz and Zhang (2003) Fundamentals of Groundwater. John Wiley and Sons Inc. , New York, pp. 592. Greenland maps: Google Earth, http: //geography. about. com/library/blank/blxgreenland. htm Global Land Cover Facility Earth Science Data Interface (http: //glcfapp. glcf. umd. edu: 8080/esdi/index. jsp) Online Isotopes in Precipitation Calculator (http: //wateriso. eas. purdue. edu/waterisotopes/pages/data_access/oipc. html) Acknowledgements Funding provided by the University of Florida Faculty Enhancement Opportunity, University of Texas Institute for Geophysics, and the NSF Graduate Research Fellowship Program. Thanks to George Kamenov for ICP-MS guidance and Amy Brown for lab assistance and general discussion.

Questions?

Questions?

Trace Metals • PG streams enriched in Cr, Mn, Fe, Co, Ni, Ba, and

Trace Metals • PG streams enriched in Cr, Mn, Fe, Co, Ni, Ba, and Pb compared to DG streams • Weathering of mafic minerals