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| Titel |
Quantifying the magnitude, spatiotemporal variation and age of aquatic CO2 fluxes in western Greenland |
| VerfasserIn |
Hazel Long, Susan Waldron, Trevor Hoey, Mark Garnett, Jason Newton |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250101610
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| Publikation (Nr.) |
 EGU/EGU2015-789.pdf |
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| Zusammenfassung |
| High latitude regions are experiencing accelerated atmospheric warming, and understanding
the terrestrial response to this is of crucial importance as: a) permafrost soils hold vast
amounts (1672 Pg; Tarnocai et al., 2009) of carbon (C) which may be released and feedback
to climate change; and, b) ice sheet melt in this region is accelerating, and whilst this will
cause albedo and heat flux changes, the role of this in atmospheric gas release is poorly
known. To understand how sensitive arctic environments may respond to future warming, we
need measurements that document current C flux rates and help to understand C cycling
pathways.
Although it has been widely hypothesised that Arctic regions may become increasingly
significant C sources, the contribution of aquatic C fluxes which integrate catchment-wide
sources has been little studied. Using a floating chamber method we directly measured CO2
fluxes from spatially distributed freshwaters (ice sheet melt, permafrost melt, and
lakes/ponds) in the Kangerlussuaq region of western Greenland during the early part of the
summer 2014 melt season. Fluxes from freshwaters with permafrost sources were in the
range -3.15 to +1.28 μmol CO2 m-2 s-1. Fluxes from a river draining the ice sheet and the
Russell Glacier were between -2.19 and +4.31 μmol CO2 m-2 s-1. These ranges show the
systems can be both sources (efflux) and sinks (influx) of CO2. Much freshwater data
worldwide shows CO2 efflux, and recording river/stream systems being a CO2 sink is
unusual.
Analysis of dissolved inorganic carbon (DIC) concentrations of the water sources
revealed higher concentrations of DIC in the meltwater of permafrost systems (0.66-1.92
mmol) than the ice melt system (0.07 to 0.17 mmol), as well as differences in the carbon
stable isotope ratio ranges (δ13C permafrost-melt, -9.5 to -1.2 permil; δ13C ice-melt, -11.7 to
7.3 permil).
Where we recorded CO2 efflux we collected effluxed CO2 for radiocarbon analysis, and
here we will present the first estimates of gas-age from ice and permafrost melt. The
measured age of the released gas, along with stable isotope ratios of the DIC, can be used to
identify the source and dominant transport processes of the CO2 in these systems.
We use these data to test the hypothesis that the age of the CO2 efflux from the
ice-meltwater will be older than that from the permafrost-meltwater because the
source of CO2 in the ice-meltwater is considered to be sintered air or trapped organic
matter.
By directly measuring aquatic CO2 efflux and age from this climatically sensitive arctic
location and quantifying drawdown in high-pH ice melt streams, we have a unique dataset
that aids understanding of key feedbacks affecting the impact of projected future climate
change. |
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