The influence of ground ice distribution on geomorphic dynamics since the Little Ice Age in proglacial areas of two cirque glacier systems Jean-Baptiste Bosson, 1 * Philip Deline, 2 Xavier Bodin, 2 Philippe Schoeneich, 3 Ludovic Baron, 4 Marie Gardent 2 and Christophe Lambiel 1 1 Institut des dynamiques de la surface terrestre, Université de Lausanne, Lausanne, Switzerland 2 Laboratoire EDYTEM, Université de Savoie, CNRS, Le Bourget-du-Lac, France 3 Institut de Géographie Alpine, PACTE/Territoire, Université Joseph Fourier, Grenoble, France 4 Institut des sciences de la Terre, Université de Lausanne, Lausanne, Switzerland Received 15 August 2013; Revised 13 October 2014; Accepted 14 October 2014 *Correspondence to: Jean-Baptiste Bosson, Institut des dynamiques de la surface terrestre, Université de Lausanne, Lausanne, Switzerland. E-mail: jean-baptiste.bosson@unil.ch ABSTRACT: Holocene glaciers have contributed to an abundance of unstable sediments in mountainous environments. In perma- frost environments, these sediments can contain ground ice and are subject to rapid geomorphic activity and evolution under condition of a warming climate. To understand the influence of ground ice distribution on this activity since the Little Ice Age (LIA), we have investigated the Pierre Ronde and Rognes proglacial areas, two cirque glacier systems located in the periglacial belt of the Mont Blanc massif. For the first time, electrical resistivity tomography, temperature data loggers and differential global position- ing systems (dGPS) are combined with historical documents and glaciological data analysis to produce a complete study of evolution in time and space of these small landsystems since the LIA. This approach allows to explain spatial heterogeneity of current internal structure and dynamics. The studied sites are a complex assemblage of debris-covered glacier, ice-rich frozen debris and unfrozen debris. Ground ice distribution is related to former glacier thermal regime, isolating effect of debris cover, water supply to specific zones, and topography. In relation with this internal structure, present dynamics are dominated by rapid ice melt in the debris- covered upper slopes, slow creep processes in marginal glacigenic rock glaciers, and weak, superficial reworking in deglaciated moraines. Since the LIA, geomorphic activity is mainly spatially restricted within the proglacial areas. Sediment exportation has occurred in a limited part of the former Rognes Glacier and through water pocket outburst flood and debris flows in Pierre Ronde. Both sites contributed little sediment supply to the downslope geomorphic system, rather by episodic events than by constant supply. In that way, during Holocene and even in a paraglacial context as the recent deglaciation, proglacial areas of cirque glaciers act mostly as sediment sinks, when active geomorphic processes are unable to evacuate sediment downslope, especially because of the slope angle weakness. Copyright © 2014 John Wiley & Sons, Ltd. KEYWORDS: proglacial area; permafrost; glacier–permafrost interaction; debris-covered glacier; ground ice; sediment transfer system Introduction Glacier shrinkage, initiated at the end of the Little Ice Age (LIA: AD 1300–1850/60 in the Alps; Ivy-Ochs et al., 2009) and accelerated since the mid 1980s, has led to the rapid growth of many pro- glacial areas worldwide (Vaughan et al., 2013). These recently deglaciated areas are incredibly dynamic and rapidly changing as a result of intensive paraglacial readjustment and high sedi- ment flux (Ballantyne, 2002; Meigs et al., 2006; Otto et al., 2009; Carrivick et al., 2013). Proglacial areas have a key role in the sediment cascade systems in mountainous environments (Geilhausen et al., 2012). As a function of their ability to transfer sediment load downslope, they can act ‘either as a sink or as a source of sediment’ (Owens and Slaymaker, 2004, p. 15). In high relief and permafrost environments, proglacial areas may have one or both of two characteristics in relation with sediment flux. First, there may be thick moraine accumulations. Repeated Holocene fluctuations of heavily debris-covered glaciers can result in the formation of moraine ramparts (also called dams, dumps or bastions: Shroder et al., 2000; Benn et al., 2003; Hambrey et al., 2008). These landforms are especially common in flatter terrain dominated by high rock walls, such as cirques or valley floors inherited from the last Pleistocene glaciation, where the linkage between the glacial and the hydrological transport systems is inefficient (Benn et al., 2003). Second, there may be strong glacier–permafrost interac- tions. As a consequence of development of polythermal glacier systems within the periglacial belt (Cuffey and Paterson, 2010) and of ice recession, massive ice, ice-cemented and ice-free sed- iments may coexist in proglacial areas (Reynard et al., 2003; Haeberli, 2005; Kneisel and Kääb, 2007; Ribolini et al., 2010). As shown by examples in mountainous and polar regions, glacier EARTH SURFACE PROCESSES AND LANDFORMS Earth Surf. Process. Landforms (2014) Copyright © 2014 John Wiley & Sons, Ltd. Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/esp.3666