Summer melt rates on Penny Ice Cap, Baffin Island: Past and recent trends and implications for regional climate

Abstract

[1] At latitude 67 N, Penny Ice Cap on Baffin Island is the southernmost large ice cap in the Canadian Arctic, yet its past and recent evolution is poorly documented. Here we present a synthesis of climatological observations, mass balance measurements and proxy climate data from cores drilled on the ice cap over the past six decades (1953 to 2011). We find that starting in the 1980s, Penny Ice Cap entered a phase of enhanced melt rates related to rising summer and winter air temperatures across the eastern Arctic. Presently, 70 to 100% (volume) of the annual accumulation at the ice cap summit is in the form of refrozen meltwater. Recent surface melt rates are found to be comparable to those last experienced more than 3000 years ago. Enhanced surface melt, water percolation and refreezing have led to a downward transfer of latent heat that raised the subsurface firn temperature by 10 C (at 10 m depth) since the mid-1990s. This process may accelerate further mass loss of the ice cap by pre-conditioning the firn for the ensuing melt season. Recent warming in the Baffin region has been larger in winter but more regular in summer, and observations on Penny Ice Cap suggest that it was relatively uniform over the 2000-m altitude range of the ice cap. Our findings are consistent with trends in glacier mass loss in the Canadian High Arctic and regional sea-ice cover reduction, reinforcing the view that the Arctic appears to be reverting back to a thermal state not seen in millennia.

Glacial Inception on Baffin Island: The Role of Insolation, Meteorology, and Topography

“…With this WRF configuration we find a reasonable reproduction of the ECMWF boundary conditions when we simulate present-day climate. Furthermore, precipitation on the coast matches observations at values of about 300 mm yr 21 , and the equilibrium line altitude is about 1400 m in our model, also agreeing with observations (Zdanowicz et al 2012). …”

“…Noah-MP (Niu et al 2011) is used for the land surface model. It includes four layers of snow and allows for refreezing, which is an important process on the Penny Ice Cap according to historical trends (Zdanowicz et al 2012). Noah-MP caps the snow water content at 2000 kg m 22 by default, and we removed this limit.…”

Greenland meltwater storage in firn limited by near-surface ice formation

“…However, similar changes in firn structure are observed in the Canadian Arctic 19,20,21 . A study of Greenland's percolation area 250 km north of our study site also indicates ice formation in the near surface 22 .…”

Glacier surface temperatures in the Canadian High Arctic, 2000–15

“…Ultimately, if the firn temperature reaches the pressure melting point, runoff from the firn may occur (Pfeffer and Humphrey, 1998). Increased rates of firn densification (Zdanowicz and others, 2012;Bezeau and others, 2013) and the growth of large ice bodies within the firn (Gascon and others, 2013b) have been observed across the Canadian Arctic in recent years. Gascon and others (2013b) speculate that this buildup of ice bodies could prevent deep penetration of meltwater into the firn and promote horizontal runoff, thereby increasing the percentage of snowmelt that runs off from higher elevation regions of ice caps.…”