『Abstract
We describe the climatology, hydrology and biogeochemistry of
an extreme nitrogen deposition event that occurred in the highly
glacierised environment of the European High Arctic during June
1999. Meteorological analysis, three-dimensional air mass trajectories
and a 3D transport model show that blocking high pressures over
Scandinavian and the rapid advection of western European pollution
toward Svalbard were sufficient to cause the most concentrated
(1.15 ppm NO3-N and 1.20 ppm NH4-N),
high magnitude (total 26 mm and up to 2.4 mm h-1 at
30 m above sea level) nitrogen deposition event on record in this
sensitive, high Arctic environment (78.91゜N, 11.93゜E). Since the
event occurred when much of the catchment remained frozen or under
snow cover, microbial utilisation of nitrogen within snow-packs
and perennially unfrozen subglacial sediments, rather than soils,
were mostly responsible for reducing N export. The rainfall event
occurred long before the annual subglacial outburst flood and
so prolonged (ca. 10 day) water storage at the glacier bed further
enhanced the microbial assimilation. When the subglacial outburst
eventually occurred, high runoff and concentrations of NO3- (but not NH4+)
returned in the downstream rivers. Assimilation accounted for
between 53 and 72％ of the total inorganic nitrogen deposited during
the event, but the annual NO3-
and NH4+ runoff yields were still
enhanced by up to 5 and 40 times respectively. Episodic atmospheric
inputs of reactive nitrogen can therefore directly influence the
biogeochemical functioning of High Arctic catchments, even when
microbial activity takes place beneath a glacier at a time when
terrestrial soil ecosystems remain frozen and unresponsive.
Keywords: Nitrogen enrichment; Arctic ecosystems; Arctic glaciers;
Meltwater biogeochemistry』
Introduction
Field site
Methods
Hydrology and hydrochemistry
Meteorology and atmospheric chemistry measurements
Trajectory modelling
Transport model
Nitrogen mass balance
Results
Hydrometeorology
Chemistry
Mass balance
Atmospheric modelling
Discussion
Atmospheric conditions responsible for the event
Biogeochemical response of the Midtre Lovenbreen（最初のeの頭に´）
catchment
Insights from nitrogen mass balance
Conclusions
Acknowledgements
References