Impact of glacier thickness in future sea-level rates from a GRACE constrained glacier model

Abstract:

Glacier volume and ice thickness information are critical inputs in glacier models for the present-day volume and transient rates of mass balance evolution. Currently, there is large uncertainty from glacier models in the projected mass loss and sea-level rates, particularly until the middle of this century. We have developed a regional glacier model based on the temperature index method and constrained by monthly observations from GRACE/GRACE-(FO) gravimetry. We incorporate glacier dynamics in the model calibration using two methods: i) volume-area scaling and ii) modeled glacier thickness information. We estimate the present and future mass loss rates from Gulf of Alaska and Canadian Archipelago using our regional model. We optimize our model based on monthly mass balance estimated from GRACE gravimetry from 2002-2016; the long-term mass loss rates are -36 ± 4 Gtyr^-1 in the Gulf of Alaska, -27 ± 2 Gtyr^-1 in the Baffin and -36 ± 4 Gtyr^-1 in the Ellesmere region. The work will assess the influence of glacier dynamics (from the two methods) in the future projected rates of mass loss. Since our regional model does not utilize direct observations in the model initialization, the model is validated against local observations. Finally, we assess the model performance based on uncertainties from the input parameters (climate reanalysis datasets), GRACE multi-year observations, and glacier dynamics in the projected sea-level estimates.