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| Titel |
Contrasting trends in floods for two sub-arctic catchments in northern Sweden – does glacier presence matter? |
| VerfasserIn |
H. E. Dahlke, S. W. Lyon, J. R. Stedinger, G. Rosqvist, P. Jansson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 16, no. 7 ; Nr. 16, no. 7 (2012-07-17), S.2123-2141 |
| Datensatznummer |
250013369
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| Publikation (Nr.) |
 copernicus.org/hess-16-2123-2012.pdf |
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| Zusammenfassung |
| Our understanding is limited to how transient changes in glacier response to
climate warming will influence the catchment hydrology in the Arctic and
Sub-Arctic. This understanding is particularly incomplete for flooding
extremes because understanding the frequency of such unusual events requires
long records of observation not often available for the Arctic and
Sub-Arctic. This study presents a statistical analysis of trends in the
magnitude and timing of flood extremes and the mean summer discharge in two
sub-arctic catchments, Tarfala and Abisko, in northern Sweden. The
catchments have different glacier covers (30% and 1%, respectively).
Statistically significant trends (at the 5% level) were identified for
both catchments on an annual and on a seasonal scale (3-months averages)
using the Mann-Kendall trend test. Stationarity of flood records was tested
by analyzing trends in the flood quantiles, using generalized least squares
regression. Hydrologic trends were related to observed changes in the
precipitation and air temperature, and were correlated with 3-months
averaged climate pattern indices (e.g. North Atlantic oscillation). Both
catchments showed a statistically significant increase in the annual mean
air temperature over the comparison time period of 1985–2009 (Tarfala and
Abisko p<0.01), but did not show significant trends in the total
precipitation (Tarfala p = 0.91, Abisko p = 0.44). Despite the similar climate
evolution over the studied period in the two catchments, data showed
contrasting trends in the magnitude and timing of flood peaks and the mean
summer discharge. Hydrologic trends indicated an amplification of the
streamflow and flood response in the highly glacierized catchment and a
dampening of the response in the non-glacierized catchment. The glacierized
mountain catchment showed a statistically significant increasing trend in
the flood magnitudes (p = 0.04) that is clearly correlated to the occurrence
of extreme precipitation events. It also showed a significant increase in
mean summer discharge (p = 0.0002), which is significantly correlated to the
decrease in glacier mass balance and the increase in air temperature
(p = 0.08). Conversely, the non-glacierized catchment showed a significant
decrease in the mean summer discharge (p = 0.01), the flood magnitudes
(p = 0.07) and an insignificant trend towards earlier flood occurrences
(p = 0.53). These trends are explained by a reduction of the winter snow pack
due to higher temperatures in the winter and spring and an increasing soil
water storage capacity or catchment storage due to progressively thawing
permafrost. |
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