Thermal Regime Change of a Retreating Polythermal Glacier from Repeat Ground Penetrating Radar

Polythermal glaciers (i.e. glaciers that consist of some combination of both warm and cold ice) are common in the Arctic (e.g. Aschwanden and Blatter, 2005). Recent work (e.g. Rippin et al. 2011; Gusmeroli et al., 2012; Wilson and Flowers, 2013; Wilson et al., 2013) has focussed on how their polythermal structure might change in response to a warming climate. These studies suggest that the nature of future thermal regime change is complex, such that the relative volume of temperate ice in a shrinking glacier may increase or decrease, depending on local geographical, meteorological and hydrological parameters.

Here, we present a unique data-set from the well-studied glacier Midtre Lovénbreen in Svalbard, which has shown continued and sustained retreat in recent years. We have a network of ground penetrating radar (GPR) lines from this glacier, first surveyed in 2006 and then repeat-surveyed along exactly the same lines in 2012. Despite significant retreat and thinning, our data suggests that minimal changes in thermal regime have taken place over this period, reinforcing previous observations of a significant lag in the rate at which the thermal regime responds to mass balance changes (cf. Rippin et al., 2011). Such a ‘thermal lag’ has implications for evolving hydrological and dynamical behaviour of these glaciers, and also for the future mass balance response. In this paper, we comment on the observed changes and consider the implications for our understanding of future thermal regime evolution.

References

Aschwanden, A., and H. Blatter. 2005. Meltwater production due to strain heating in Storglaciären, Sweden. JGR, 110, doi:10.1029/2005JF000,328.

Rippin, D.M., J.L. Carrivick and C. Williams. 2011. Evidence towards a thermal lag in the response of Kårsaglaciären, northern Sweden, to climate change.  J. Glac., 57(205), 895-903.

Gusmeroli, A., P. Jansson, R. Pettersson and T. Murray. 2012. Twenty years of cold surface layer thinning at Storglaciaren, sub-Arctic Sweden, 1989-2009. J. Glac., 58(207), 3-10.

Wilson, N.J., G.E. Flowers and L. Mingo. 2013. Comparison of thermal structure and evolution between neighboring subarctic glaciers. JGR, 118(3), 1443-1459.

Wilson, N.J. and G.E. Flowers. 2013. Environmental controls on the thermal structure of alpine glaciers. The Cryosphere, 7(1), 167-182.