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Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments


Title (Dublin Core)

Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments

Description (Dublin Core)

<p>Climate change is affecting the rate of carbon cycling,
particularly in the Arctic. Permafrost degradation through deeper thaw and
physical disturbances results in the release of carbon dioxide and methane to
the atmosphere and to an increase in lateral dissolved organic matter (DOM)
fluxes. Whereas riverine DOM fluxes of the large Arctic rivers are well
assessed, knowledge is limited with regard to small catchments that cover
more than 40&thinsp;% of the Arctic drainage basin. Here, we use absorption
measurements to characterize changes in DOM quantity and quality in a low
Arctic (Herschel Island, Yukon, Canada) and a high Arctic (Cape Bounty,
Melville Island, Nunavut, Canada) setting with regard to geographical
differences, impacts of permafrost degradation, and rainfall events. We find
that DOM quantity and quality is controlled by differences in vegetation
cover and soil organic carbon content (SOCC). The low Arctic site has higher
SOCC and greater abundance of plant material resulting in higher
chromophoric dissolved organic matter (cDOM) and dissolved organic carbon
(DOC) than in the high Arctic. DOC concentration and cDOM in surface waters
at both sites show strong linear relationships similar to the one for the
great Arctic rivers. We used the optical characteristics of DOM such as cDOM
absorption, specific ultraviolet absorbance (SUVA), ultraviolet (UV)
spectral slopes (S275–295), and slope ratio (SR) for assessing quality
changes downstream, at base flow and storm flow conditions, and in relation to
permafrost disturbance. DOM in streams at both sites demonstrated optical
signatures indicative of photodegradation downstream processes, even over
short distances of 2000&thinsp;m. Flow pathways and the connected hydrological
residence time control DOM quality. Deeper flow pathways allow the export of
permafrost-derived DOM (i.e. from deeper in the active layer), whereas
shallow pathways with shorter residence times lead to the export of fresh
surface- and near-surface-derived DOM. Compared to the large Arctic rivers,
DOM quality exported from the small catchments studied here is much fresher
and therefore prone to degradation. Assessing optical properties of DOM and
linking them to catchment properties will be a useful tool for understanding
changing DOM fluxes and quality at a pan-Arctic scale.</p>

Creator (Dublin Core)

C. Coch
B. Juhls
S. F. Lamoureux
M. J. Lafrenière
M. Fritz
B. Heim
H. Lantuit

Subject (Dublin Core)


Publisher (Dublin Core)

Copernicus Publications

Date (Dublin Core)


Type (Dublin Core)


Identifier (Dublin Core)


Source (Dublin Core)

Biogeosciences, Vol 16, Pp 4535-4553 (2019)

Language (Dublin Core)


Relation (Dublin Core)

Provenance (Dublin Core)

Journal Licence: CC BY