Réf. Stott & Mount 2006 - A

Référence bibliographique complète
STOTT T., MOUNT N. Alpine proglacial suspended sediment dynamics in warm and cool ablation seasons: Implications for global warming. Journal of Hydrology, 2006, Vol. 332, N°3-4, p. 259-270.

Abstract: Data on suspended sediment dynamics and loads obtained from the Torrent du Glacier Noir, Ecrins Massif, SE France, during the unusually warm 2003 and cooler 2004 ablation seasons are used to indicate the likely future impacts of climate warming on suspended sediment transport processes in temperate Alpine proglacial zones. Mean daily air temperature was 1.2 °C higher in 2003, mean streamflow of the Torrent du Glacier Noir was 2.3 times greater and the suspended sediment concentrations was between 3.1 and 4.1 times greater in July 2003, than for the same period in the 2004 ablation season.

Mots-clés
Suspended sediment load, Alpine, proglacial, global warming.

Organismes / Contact
Physical Geography and Outdoor Education, Liverpool John Moores University, I.M. Marsh Campus, Barkhill Road, Liverpool L17 6BD, United Kingdom. t.a.stott@ljmu.ac.uk
GIS/Physical Geography, School of Geography, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom. Nick.Mount@nottingham.ac.uk

(1) - Paramètre(s) atmosphérique(s) modifié(s)
(2) - Elément(s) du milieu impacté(s)
(3) - Type(s) d'aléa impacté(s)
(3) - Sous-type(s) d'aléa
Temperature Rivers    

Pays / Zone
Massif / Secteur
Site(s) d'étude
Exposition
Altitude
Période(s) d'observation
France Ecrins massif Torrent du Glacier Noir     2003-2004

(1) - Modifications des paramètres atmosphériques
Reconstitutions
 
Observations
 
Modélisations
 
Hypothèses
 

Informations complémentaires (données utilisées, méthode, scénarios, etc.)



(2) - Effets du changement climatique sur le milieu naturel
Reconstitutions
 
Observations
Comparison of 16-day monitoring periods in July 2003 and July 2004 showed that mean daily AT measured 1 km from the snout of the Glacier Noir was 1.2 °C higher in 2003, mean Q of the Torrent du Glacier Noir was 2.3 times greater and the SSL was between 3.1 and 4.1 times greater in July 2003, than for the same period in the 2004 ablation season. There is an increase in SSC during the 2004 observation period which is less apparent in 2003, most likely because higher ATs and consequently higher Q earlier in the 2003 melt season had removed available sediment before the study took place in July.

The rating curve method for estimating SSL (SSL QR) produced a total load for the 16-day study period in 2003 which, when corrected upwards to account for statistical bias, was 10314 ± 743 t or 95% of the SSL estimated from the turbidity record (SSLT) for the same period. In 2004 the corrected SSLQR estimate was 2 504 ± 126 t, while that from the 0–10000 mg/L range turbidity probe was tentatively 743 ± 122 t, and the estimate from a low range (0–750 mg/ L). Partech turbidity probe deployed at the site was 3474 ± 302 t. While the two SSL estimation methods in 2004 are not in perfect agreement, the contrasts between the two seasons is nevertheless very clear and is largely attributed to a mean monthly regional AT increase of ~2.0 °C over most of the 2003 ablation, perhaps combined with greater winter snowfall. The July 2003 SSL record, compared with July 2004, can be used to gain an insight into the impact of higher air temperatures on SSL.

It invites parallels to be drawn between the results from this study and likely impacts of higher alpine summer temperatures as a result of global warming. Such changes in SSLs have important implications for sediment transfer from mountain to piedmont zones, for stream ecology, for downstream channel stability and flood risk and for the hydro-electric industry.
Modélisations
 
Hypothèses
 

Sensibilité du milieu à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)
Streamflow and suspended sediment concentrations in function of temperature
In this study streamflow (Q) and suspended sediment concentrations (SSC) in a proglacial stream in the Ecrins National Park were monitored in the summers of 2003 and 2004.

Summer 2003 was exceptionally hot in France and adjacent countries, and the study uses this as a possible indication of future conditions under global warming. A lapse rate relationship established during July 2004 between Embrun daily mean temperatures and those at the study site is used to predict daily mean temperatures at the study site, which for June, July and August 2003, can be seen to be substantially higher than both 2004 and the 1997–2005 mean. The July 2003 and 2004 daily mean averages were 13.8 and 12.6°C, respectively. Based on this contrast in air temperatures between the 2003 and 2004 melt seasons, this study aimed to quantify the differences in streamflow, sediment load, and sediment dynamics between a ‘future’ warmer scenario, as witnessed in 2003 and ‘present’ conditions, as in 2004.


SSC and Q were continuously monitored for 16-day periods during July 2003 and July 2004. SSC was monitored by automated pump sampling during diurnal events in each season and supplemented by a 10 min turbidity record. Q was monitored at a range of flows and a rating curve used to convert a 10 min water level record into Q. Air temperature (AT) was also logged at 10 min intervals throughout the study.

(3) - Effets du changement climatique sur l'aléa
Reconstitutions
 
Observations
 
Modélisations
 
Hypothèses
 

Paramètre de l'aléa
Sensibilité du paramètres de l'aléa à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)
 
 

(4) - Remarques générales



(5) - Syntèses et préconisations