Abstract
ABSTRACTWe study the evolution of the Juneau Icefield, one of the largest icefields in North America (>3700 km2), using the Parallel Ice Sheet Model (PISM). We test two climate datasets: 20 km Weather Research and Forecasting Model (WRF) output, and data from the Scenarios Network for Alaska Planning (SNAP), derived from spatial interpolation of observations. Good agreement between simulated and observed surface mass balance was achieved only after substantially adjusting WRF precipitation to account for unresolved orographic effects, while SNAP's climate pattern is incompatible with observations of surface mass balance. Using the WRF data forced with the RCP6.0 emission scenario, the model projects a decrease in ice volume by 58–68% and a 57–63% area loss by 2099 compared with 2010. If the modeled 2070–99 climate is held constant beyond 2099, the icefield is eliminated by 2200. With constant 1971–2010 climate, the icefield stabilizes at 86% of its present-day volume. Experiments started from an ice-free state indicate that steady-state volumes are largely independent of the initial ice volume when forced by identical scenarios of climate stabilization. Despite large projected volume losses, the complex high-mountain topography makes the Juneau Icefield less susceptible to climate warming than low-lying Alaskan icefields.
Highlights
Glaciers in Alaska and adjacent Yukon and British Columbia (∼87 000 km2; Kienholz and others, 2015) are substantial contributors to sea level rise
Juneau Icefield combines the characteristics of an ice cap and mountain glaciers leading us to question which of the two feedbacks will dominate under future climate conditions
This exceeds the range of 18–45% projected for all Alaskan glaciers with 14 general circulation models for RCP4.5 and RCP8.5 scenarios by Radić and others (2013)
Summary
Glaciers in Alaska and adjacent Yukon and British Columbia (∼87 000 km; Kienholz and others, 2015) are substantial contributors to sea level rise. Large icefields mantling complex mountainous topographies with strong relief are common in Alaska (e.g. Harding Icefield, Juneau Icefield, Stikine Icefield) Accurate projections of their mass changes are important for assessing the future contribution of Alaska’s glaciers to sea level rise. As outlet glaciers retreat, lowlying, high-ablating parts of the icefield are lost, leading to less negative icefield-wide specific mass balances. This stabilizing (negative) feedback competes with a destabilizing (positive) feedback due to glacier-wide thinning commonly referred to as the Bodvardsson effect (Bodvarsson, 1955) or climate-elevation feedback. Juneau Icefield combines the characteristics of an ice cap and mountain glaciers leading us to question which of the two feedbacks will dominate under future climate conditions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
