Subglacial Conditions on Lomonosovfonna Vary Spatially with Tidewater Glaciers Nordenskiöldbreen and Negribreen

Sammanfattning

Lomonosovfonna is a high-altitude ice field on Svalbard archipelago, interconnected with multipleoutlet glaciers of varying ice dynamics. The polar region is characterised by its high population ofsurging glaciers, which undergo semi-regular cycles of drastically altered ice flow; months—multiannual long active surge phases with extreme ice velocities, followed by longer inactive phases ofslow ice flow, typically in a multidecade manner. The underlying causes of glacier surges are yetrelatively unknown but are hypothesised to be related to subglacial hydrological systems and thermalstates, two conditions with closely related mechanics. As bed echo intensity varies with the presence orabsence of liquid water at the ice-bed contact, radio echo sounding can be used to survey subglacialconditions. Impulse radar data collected over Lomonosovfonna, was analysed in the aim to examine aspatial variation of subglacial water. Strong echo intensity of emitted radar signals is assumed tocorrespond to wetter conditions, whereas weak reflectivity points towards an absence of subglacialwater. Excessive subglacial water affects long-term ice dynamics and mass balance by increased basalsliding. This study suggests that the distribution of subglacial water, between the basin areas ofNordenskiöldbreen and Negribreen, fed by the Lomonosovfonna ice field, varies spatially. It was foundthat the prevalence of liquid water at the ice-bed interface varies in an east west direction, coincidingwith the two different catchment areas. Data points intersecting Negribreen exhibit higher bedreflectivity as compared to those intersecting Nordenskiöldbreen, reflecting the nature of their icedynamics. The results strengthen the theory that subglacial drainage versus meltwater input at the icebed interface plays a crucial role in the glaciers’ respective tendency to exhibit stable state or surge.