CENPERM Seminar – University of Copenhagen

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Center for Permafrost (CENPERM) > Events > Events 2017 > Previous Events 2017 > CENPERM Seminar

CENPERM Seminar

Prof. Ellen Martin and Prof. Jon Martin, University of Florida
Neglected fluxes: Understanding the evolution of weathering as the Greeland Ice Sheet retreats.

Recent studies document extreme fluxes of bioavailable nutrients sourced to the ocean from proglacial rivers draining the Greenland Ice Sheet (GrIS). However, little is known of fluxes from deglaciated watersheds that are disconnected from the GrIS and drain only local precipitation and active layer melt. These two types of watersheds have distinct water:rock ratios, sediment exposure ages, and climate conditions. Changes in relative contributions from proglacial and deglaciated watersheds may drive previously observed increases in deep sea Pb isotope records over the past 25,000 yrs. Therefore, we hypothesize that changes in watershed contributions associated with ice retreat produce variations in isotopic, nutrient, and CO2 fluxes. To test this hypothesis, we sampled gases, water, stream bedload, and bedrock from two proglacial and nine deglaciated watersheds in the Kangerlussuaq, Sisimiut and Narsarsuaq regions during field deployments in 2013 and 2017. We also gauged several deglaciated streams in 2017. We will present data that suggest (1) changes in radiogenic isotope ratios reflect the extent of weathering in each watershed, (2) CO2 consumption through weathering decreases with increased weathering extent, (3) hyporheic zones are the site of much weathering in proglacial rivers, and (4) proglacial discharge can be both a source and sink of CO2 and CH4. These results have implications for understanding past ice sheet dynamics and future impacts of ice sheet retreat on isotopic, nutrient and CO2 fluxes.

Everybody is welcome, no registration.