REMNANT OF THE ICE AGE MEETS 21ST CENTURY CLIMATE: MODELING OF THE FORM, FLOW, AND FUTURE OF BARNES ICE CAP, BAFFIN ISLAND, CANADA (Invited Presentation)

As one of the last remnants of the Laurentide Ice Sheet, the 5800 m² Barnes Ice Cap in central Baffin Island, Nunavut, Canada, owes a good deal of its form, flow, and existence to climates of the past. In-situ data from the 1960s-1980s, combined with more recent airborne and satellite observations, provide an unusually rich platform for investigating the stability of the ice cap and projecting its future evolution. We use a three-dimensional thermomechanical ice-flow model to simulate steady state and transient configurations of Barnes Ice Cap in response to historical, modern and future climates. The model includes a basal friction law to account for variable basal sliding, and accounts for viscosity contrasts between the softer Pleistocene- and stiffer Holocene ice. It is coupled to a calibrated model of surface mass-balance that translates air temperature and precipitation into mass loss or gain, and demonstrates a pronounced sensitivity of the ice cap to temperature over precipitation.

Millennial-scale sensitivity tests reveal a tendency for the ice cap to adjust its form from elongate to radial, highlighting the imprint of inherited ice-cap geometry. Ice dynamics play a significant role on these timescales, with basal sliding exerting almost twice the influence on ice-cap evolution as Pleistocene versus Holocene ice viscosity. Situated on a low and gently sloping bed, Barnes Ice Cap has maintained a stable configuration over the last ~2000 by virtue of its own topography through the feedback between mass balance and elevation. Simulations show that the 1960-2013 mean climate has crossed a threshold of ice-cap viability, and that under projected future climates, Barnes Ice Cap will likely disappear within 300 years. Ice dynamics play almost no role in the ice cap’s projected demise given the rapid pace of warming. This picture of a stagnating ice mass rapidly melting on the landscape contrasts with that of the modern continental ice sheets, where dynamic mass losses are important, and in some places, dominant. It may be representative, however, of the behavior of other Arctic glaciers and ice caps, which are expected to be key contributors to 21^st century sea-level rise.