10:45 AM - 12:15 PM
[ACC25-P06] Changes in the ice flow regime of Qaanaaq Glacier, northwestern Greenland
Keywords:glaciology, glacier, flow model
Glaciers and ice caps surrounding Greenland is rapidly losing mass. Mass loss of the glaciers affects the ice flow regime, and in turn flow changes affect glacier mass loss. Therefore, we need to observe flow velocity for a long period to understand mass changes of glaciers and ice caps. To investigate glacier mass loss and dynamics, we have studied Qaanaaq Glacier, northwestern Greenland since 2012. Because of recently increasing glacial meltwater discharge, the outlet streams of Qaanaaq Glacier flooded and destroyed a bridge and a road in 2015 and 2016. Thus, glacier changes are relevant to the local community in Qaanaaq. This study analyzes ice flow speed observed on Qaanaaq Glacier over the past decade and perform numerical modeling to reproduce past glacier changes.
Qaanaaq Glacier is one of the outlet glaciers of the Qaanaaq ice cap situated in northwestern Greenland (77°28'N, 69°13'W). On the glacier, we have performed field observations since 2012, including flow velocity and surface mass balance measurements. We installed aluminum poles at six locations (Site1–6) between 243 and 968 m a.s.l. The poles were surveyed in July or August in 2012–2022 (no survey in 2021 because of COVID-19) with a GNNS antenna and coordinates of the poles were obtained. The mean annual horizontal velocity was calculated from the displacement of the poles.
A glacier flow model was developed for the vertical cross section along the central flowline of Qaanaaq Glacier. The model computes two-dimensional flow velocities with the finite element method. The flow parameters used in the model were calibrated by the observed horizontal velocities. Glacier surface elevation and front position were updated by the observed surface mass balance and the modeled flow velocity to generate a geometry for the next time step. Velocity calculation and geometry update were repeated with a temporal resolution of one year.
Our observations indicated deceleration in the horizontal flow velocities at Sites 1–4. The change in flow velocity was the most significant at Site 3, showing a change from 20.54 m a−1 to 18.90 m a−1 over the 10 years. The flow rates at Sites 5 and 6 showed a slight increase after 2016. The model experiment showed that Qaanaaq Glacier retreated by 92 m over a decade, which was 15 m smaller than the observation. The calculated average surface elevation change over the 10 years was less negative than the observation.
Based on the initial results, we are in the process to improve the glacier model. In the presentation, we are going to report further experiments to reproduce the observed elevation and front position changes. The goal of our study is to clarify the influence of the changes in the ice dynamics on the recent thinning and retreat.
Qaanaaq Glacier is one of the outlet glaciers of the Qaanaaq ice cap situated in northwestern Greenland (77°28'N, 69°13'W). On the glacier, we have performed field observations since 2012, including flow velocity and surface mass balance measurements. We installed aluminum poles at six locations (Site1–6) between 243 and 968 m a.s.l. The poles were surveyed in July or August in 2012–2022 (no survey in 2021 because of COVID-19) with a GNNS antenna and coordinates of the poles were obtained. The mean annual horizontal velocity was calculated from the displacement of the poles.
A glacier flow model was developed for the vertical cross section along the central flowline of Qaanaaq Glacier. The model computes two-dimensional flow velocities with the finite element method. The flow parameters used in the model were calibrated by the observed horizontal velocities. Glacier surface elevation and front position were updated by the observed surface mass balance and the modeled flow velocity to generate a geometry for the next time step. Velocity calculation and geometry update were repeated with a temporal resolution of one year.
Our observations indicated deceleration in the horizontal flow velocities at Sites 1–4. The change in flow velocity was the most significant at Site 3, showing a change from 20.54 m a−1 to 18.90 m a−1 over the 10 years. The flow rates at Sites 5 and 6 showed a slight increase after 2016. The model experiment showed that Qaanaaq Glacier retreated by 92 m over a decade, which was 15 m smaller than the observation. The calculated average surface elevation change over the 10 years was less negative than the observation.
Based on the initial results, we are in the process to improve the glacier model. In the presentation, we are going to report further experiments to reproduce the observed elevation and front position changes. The goal of our study is to clarify the influence of the changes in the ice dynamics on the recent thinning and retreat.